U.S. patent application number 09/952089 was filed with the patent office on 2002-03-07 for wavy composite tubular structures.
Invention is credited to Pratt, William F..
Application Number | 20020028332 09/952089 |
Document ID | / |
Family ID | 26941384 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020028332 |
Kind Code |
A1 |
Pratt, William F. |
March 7, 2002 |
Wavy composite tubular structures
Abstract
Construction and advantages of tubular structures made from wavy
composite, conventional composites, and damping materials is
revealed. The use of sinuous or wavy composite structures as a
capable replacement for crossply laminates is disclosed. By
combining wavy composite laminae in various waveforms, offsets,
angular orientations and material combinations, it is possible to
provide axial, torsion, or shear properties equivalent to
unidirectional materials but without the limitations related to
fiber discontinuity, labor costs for fabrication, and weakness at
seams where laminates overlap. Several examples of both wavy
crossply laminates and unidirectional crossply laminates are
analyzed and compared.
Inventors: |
Pratt, William F.; (Pleasant
Grove, UT) |
Correspondence
Address: |
Thompson E. Fehr
Suite 300
Goldenwest Corporate Center
5025 Adams Avenue
Ogden
UT
84403
US
|
Family ID: |
26941384 |
Appl. No.: |
09/952089 |
Filed: |
September 10, 2001 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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09952089 |
Sep 10, 2001 |
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09238873 |
Jan 27, 1999 |
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6287664 |
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60027975 |
Oct 9, 1996 |
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60240645 |
Oct 16, 2000 |
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60251094 |
Dec 1, 2000 |
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Current U.S.
Class: |
428/364 |
Current CPC
Class: |
A63B 2209/02 20130101;
B29L 2031/52 20130101; Y02T 50/40 20130101; B29C 70/16 20130101;
B64C 27/473 20130101; F16D 3/50 20130101; F16F 9/306 20130101; F16C
2326/06 20130101; B29K 2995/0046 20130101; A63B 60/00 20151001;
A63C 5/075 20130101; A63B 59/50 20151001; B64C 1/12 20130101; B32B
1/00 20130101; B63B 2231/52 20130101; B32B 5/12 20130101; B64C
2001/0072 20130101; A63B 60/54 20151001; F16C 2326/43 20130101;
Y10T 428/2913 20150115; A01K 87/00 20130101; B29C 70/086 20130101;
B63H 23/34 20130101; A63C 5/07 20130101; B63B 32/57 20200201; B63B
5/24 20130101; B64C 2027/4736 20130101; A63B 53/10 20130101; A63B
2102/18 20151001; F16C 3/026 20130101; B29L 2031/5263 20130101;
B64C 1/066 20130101 |
Class at
Publication: |
428/364 |
International
Class: |
D02G 003/00 |
Claims
What I claim as my invention is:
1. A golf club shaft, which comprises: a shaft; a viscoelastic
layer having a side attached to a surface of said shaft; and a
sinuous wavy composite layer attached to said viscoelastic layer on
a side opposite to the side of said viscoelastic layer that is
adjacent to said shaft.
Description
BACKGROUND OF THE INVENTION
[0001] The control of noise and vibration in composite structures
is an important area of current research in aerospace, automotive
and other industries. For example, spacecraft vibrations initiated
by attitude adjusting thrusters, motors and thermally induced
stresses inhibit accurate aiming of antennas and other equipment
carried by the craft. Such vibrations can cause severe damage to
the craft and its associated equipment. Fatigue failure of
structural components can occur at stresses well below static load
limits.
[0002] Traditional passive noise and vibration control methods are
heavy, bulky, and perform only marginally. For example, the
acoustics of aerospace vehicles during launch are severe enough to
cause damage to payloads and guidance control systems and could
cause failure of the mission. Typically, standard metallic and
composite technologies rely upon the use of heavy acoustic blankets
to reduce the damaging effects of sound pressure fields during
launch. Structurally amplified acoustic and vibration energy
exacerbates the problem due to low inherent damping in fairings and
other structural components. A practical way of increasing damping
and improving acoustic properties in mechanical structures is
required.
[0003] Composite materials have been used to construct a wide
variety of structural elements, including tubes, enclosures, beams,
plates and irregular shapes. Objects as diverse as rocket motor
housings and sporting goods, notably skis, archery arrows, vaulting
poles and tennis rackets have been structured from composite
materials. While composite constructions have offered many
significant advantages, such as excellent strength and stiffness
properties, together with light weight, the poor vibration damping
properties of such construction have been of concern.
[0004] The invention relates to fiber reinforced composite
structures and applications that use wavy fiber patterns in the
plane of the laminate, and that increase damping with little or no
sacrifice in strength.
[0005] The invention also relates to the methods and apparatus for
manufacturing the aforementioned composite material structures.
[0006] Another aspect of the invention is directed toward the
fabrication of a wavy fiber pre-preg (fibers preimpregnated with
epoxy resin). Such pre-pregs not only have an aesthetic appeal but
also may be fabricated with selected variable volume fractions to
accommodate a variety of applications.
[0007] The present invention relates to fiber reinforced resin
matrix composites, and more particularly, to improved crossply
laminate structures made from wavy composite materials. Such
materials and structures made from wavy composites have enhanced
structural properties and represent a greatly enhanced method of
manufacturing crossply laminates.
[0008] Fiber reinforced resin matrix composites have been used for
decades to provide stiff and strong lightweight structures to a
wider field of applications in aerospace, sports, automotive,
marine, civil infrastructure, and consumer markets. Favorable
characteristics include high stiffness and strength to weight
ratios, corrosion resistance, and tailorable structural properties.
Disadvantages primarily involve cost, especially labor costs in
fabricating practical structures.
[0009] Because of its anisotropy, fiber reinforced composites can
be used to tailor the properties of the structure to the expected
loads in a very efficient manner, especially if structural loads
are limited to bending only, axial loads only, or torsion loads
only, etc. When applied loads on a structure are uncertain or are
known but involve many modes (i.e. axial, bending, and torsion for
example) then in these cases, careful design and multiple fiber
orientations are necessary to prevent failure of the structure. In
these cases, multiple fiber orientations can give the structure of
the composite properties that range from anisotropic to
quasi-isotropic to isotropic depending on the materials or laminate
structure (Hyer 1997).
[0010] There are three basic methods used to obtain isotropy or
near-isotropy in composite structures. These three methods use
special materials such as chopped fiber mats and woven fiber cloth,
filament winding, and ply stacking of oriented cloth or
unidirectional pre-preg. Each method has its advantages and
disadvantages. Fiber mats or sprayed chopped fibers are easy to use
and give near isotopic properties but cannot be used to tailor the
stiffness and strength properties of composites to efficiently
resist loads and are not typically used in other than light loading
conditions.
[0011] Woven fiber cloth can be made in a number of fiber
orientations, weights, and weaves, and can be tailored to a degree
but are typically more expensive, usually require manual lay-up
fabrication methods, and can limit the flexibility of the design if
the fiber orientation is not optimal for the particular
application. Additionally, woven cloth fibers are typically cut,
interrupting fiber continuity especially where primary orientation
of the fiber must be changed abruptly.
[0012] Filament winding methods offer continuity of fibers and
automation as primary advantages but can present significant
difficulties in obtaining the necessary fiber orientations for
efficient structural properties. In these cases, it is customary to
interrupt the fiber continuity to add layers of unidirectional
pre-preg to accomplish the desired structural properties.
Additional disadvantages include significant investment in capital
and other fabrication issues.
[0013] Ply stacking of unidirectional and/or woven cloth offers the
most flexible method of making composite structures that meet the
desired properties of the structure. Advantages include not only
flexible manufacturing, but include ease in compaction, more
uniform properties, and minimal investment in capital equipment.
Disadvantages include interruption of fiber continuity, and high
labor costs (Reinfelder, Jones et al. 1998) Therefore, a need
exists for a method and a composite structure that provides
multiple fiber orientations, has the characteristics of ply-stacked
composite structures, can be automated, and minimizes or eliminates
the interruption of fibers.
[0014] The present invention relates to fiber reinforced resin
matrix composites, and more particularly, to improved tubular wavy
composite based laminate structures with high damping, and improved
torsional properties. The present invention relates to a
generalized tubular wavy composite structure that is easier to
manufacture, and can be used to create high quality, high
capability, golf club shafts, baseball bats, automotive drive
shafts, helicopter drive shafts, fishing rods, oil drilling pipe,
and other tubular or structural members where damping, stiffness,
and strength are important.
DESCRIPTION OF RELATED ART
[0015] The following terms used herein will be understood to have
their ordinary dictionary meaning as follows:
[0016] Composite: made up of distinct parts. In the general sense,
refers to any fiber reinforced material but especially any cured
fiber reinforced matrix structure.
[0017] Crossply, crossply lay-up, or crossply laminate: Two or more
laminae made from unidirectional pre-preg arranged in such a manner
that the primary direction of the fiber or strong material
direction in the layers differ in orientation, or "cross" each
other.
[0018] Fiber: a thread or a structure or object resembling a
thread. A slender and greatly elongated natural or synthetic
filament. (Includes metal fibers)
[0019] Lamina(te): a thin plate . . . : layer(s)
[0020] Matrix: material in which something is enclosed or
embedded.
[0021] Offset: In the context of this invention, means a
generalized lead or lag of one waveform relative to another,
similar to a phase angle in electronic engineering.
[0022] Off-axis: In the context of this invention, means a
rotational difference of the strong axis between one laminae
waveform relative to another or some reference.
[0023] Pre-preg: Fiber reinforced, resin matrix impregnated
materials where the matrix is partially cured and ready for use. A
special "uncured" case of the more general term "Composite".
[0024] Resin: an uncured binder, especially an uncured polymer
binder or matrix used to bind fibers or fibrous materials; the
matrix component of an uncured pre-preg.
[0025] Viscoelastic: having appreciable and conjoint viscous and
elastic properties. Note: a special case of the term "viscoelastic"
is "anisotropic viscoelastic", which is a viscoelastic material
reinforced with fibers that give the material anisotropic
properties. When the term viscoelastic is used in the text it
should be construed to encompass this special case.
[0026] Wavy crossply, wavy crossply lay-up, or wavy crossply
laminate: Two or more wavy fiber laminae arranged in such a manner
that the primary direction of the fiber or strong material
direction in the layers differ in orientation.
[0027] Wavy: The pattern of fiber lay that has a sinusoidal look,
especially a sinuous wavy fiber in the plain of a laminate; the
wave pattern need not be periodic or uniform.
[0028] Composite: made up of distinct parts. In the general sense,
refers to any fiber reinforced material but especially any cured
fiber reinforced matrix structure.
[0029] Crossply, crossply lay-up, or crossply laminate: Two or more
laminae made from unidirectional pre-preg arranged in such a manner
that the primary direction of the fiber or strong material
direction in the layers differ in orientation, or "cross" each
other.
[0030] Fiber: a thread or a structure or object resembling a
thread. A slender and greatly elongated natural or synthetic
filament. (Includes metal fibers)
[0031] Lamina(te): a thin plate . . . : layer(s)
[0032] Matrix: material in which something is enclosed or
embedded.
[0033] Offset: In the context of this invention, means a
generalized lead or lag of one waveform relative to another,
similar to a phase angle in electronic engineering.
[0034] Off-axis: In the context of this invention, means a
rotational difference of the strong axis between one laminae
waveform relative to another or some reference.
[0035] Pre-preg: Fiber reinforced, resin matrix impregnated
materials where the matrix is partially cured and ready for use. A
special "uncured" case of the more general term "Composite".
[0036] Resin: an uncured binder, especially an uncured polymer
binder or matrix used to bind fibers or fibrous materials; the
matrix component of an uncured prepreg.
[0037] Viscoelastic: having appreciable and conjoint viscous and
elastic properties. Note: a special case of the term "viscoelastic"
is "anisotropic viscoelastic", which is a viscoelastic material
reinforced with fibers that give the material anisotropic
properties. When the term viscoelastic is used in the text it
should be construed to encompass this special case.
[0038] Wavy crossply, wavy crossply lay-up, or wavy crossply
laminate:
[0039] Two or more wavy fiber laminae arranged in such a manner
that the primary direction of the fiber or strong material
direction in the layers differ in orientation.
[0040] Wavy: The pattern of fiber lay that has a sinusoidal look,
especially a sinuous wavy fiber in the plain of a laminate; the
wave pattern need not be periodic or uniform.
[0041] Fiber: a thread or a structure or object resembling a
thread. A slender and greatly elongated natural or synthetic
filament. (Includes metal fibers)
[0042] Matrix: material in which something is enclosed or
embedded.
[0043] Viscoelastic: having appreciable and conjoint viscous and
elastic properties. Note: a special case of the term "viscoelastic"
is "Anisotropic Viscoelastic", defined below. When the term
viscoelastic is used in the following text it should be construed
to encompass this special case.
[0044] Lamina(te): a thin plate . . . : LAYER(S)
[0045] Composite: made up of distinct parts.
[0046] CWC: (Continuous Wave Composite) defines any fiber-matrix
combination having at least one fiber without a break (or
interruption) and having a pattern which can be defined by a
mathematical algorithm. It generally has a wavy appearance. It can
consist of "unidirectional" fibers (although in this case the
fibers would be placed in a wavy pattern) or woven cloth (which
also will have a wavy pattern to the warp or weft).
[0047] CWCV: (Continuous Wave Composite Viscoelastic) defines a
combination of CWC and viscoelastic materials designed to induce
damping in a structure.
[0048] CWC-AV: (Anisotropic Viscoelastic) defines a viscoelastic
material or matrix with an embedded wavy fiber pattern. Such a
material would have anisotropic, elastic, and viscoelastic
properties. It is a special case of both CWC laminates and
"viscoelastic" and can be used in conjunction with conventional CWC
fiber-matrix combinations to provide damping and unique structural
properties. Any use of "CWC" or "viscoelastic" in the following
text can be construed to encompass this special case.
[0049] One of the simplest and often very effective passive damping
treatments involves the use of thermo-viscoelastic (TVE) materials.
These materials, represented by Avery-Dennison's FT series (FT-1191
is one example), exhibit both elastic and dissipative qualities
which make them useful in a number of passive damping
treatments.
[0050] Some of the first uses of thermo-viscoelastic materials to
increase structural damping involved the use of surface patches of
aluminum foil and viscoelastic adhesives. Called constrained or
embedded-layer damping, these methods produce modest gains in
damping.
[0051] One of the more common passive damping methods, Constrained
Layer Damping or CLD (Kerwin, 1959), is achieved by bonding a thin
layer of metal sheet, usually aluminum, to an existing structure
with a viscoelastic adhesive. Shear strains develop in the
viscoelastic material when the original structure bends or extends.
Damping occurs when the deformation of the viscoelastic adhesive
creates internal friction in the viscoelastic material, generating
heat and thus dissipating energy.
[0052] Compared to an undamped structure, this approach, is
modestly successful but its effectiveness decreases markedly as the
ratio of the thickness of the base structure to the thickness of
the viscoelastic material increases (Hwang and Gibson, 1992). Thus
surface treatments alone cannot provide significant levels of
damping to structural members where greater strength and stiffness
are important. Hwang and Gibson (1992) reported this problem and
showed that the advantage of aluminum foil viscoelastic constrained
layer damping was eclipsed by the inherent damping in conventional
composites when the required thickness of the structure exceeds
about eight millimeters (0.3 inches). They determined that a
.+-.45.degree. graphite/epoxy composite provided approximately
uniform damping of about 1.5% in thick sections, that was at least
one order of magnitude greater than comparable aluminum
structures.
[0053] Co-cured composite-viscoelastic structures are formed when
layers of uncured fiber composites and TVE (thermal-viscoelastic or
viscoelastic) materials are alternately stacked and cured together
in an oven. Damping occurs in these structures when a load causes
differential movement of the opposing laminates, causing shearing
in the sandwiched viscoelastic material. The various methods that
use this concept of differential shearing of the viscoelastic
material can be classified by the fiber orientation methods used to
induce damping in the TVE material.
[0054] Conventional angled ply composite designs use .+-..theta.
lay-ups of straight fiber pre-preg materials to encase the
viscoelastic layers, and were first proposed by Barrett (1989) in a
design for damped composite tubular components. Barrett combined
the concepts of constrained layer damping with anisotropic shear
coupling in the constraining composite layers to create a tube that
achieved both high damping and high axial stiffness. Barrett's
research showed that maximum shearing was experienced at the ends
of the tubes and that clamping the constraining layers of the tube
at the ends eliminated much of the damping effect, rendering the
design impractical for most applications.
[0055] Chevron patterned designs also use conventional angled ply
(.+-..theta.) composite lay-ups of straight fibers but vary the
fiber orientation several times throughout the structure in a given
laminate. Called SCAD (Stress Coupled Activated Damping), it was
first proposed by Benjamin Dolgin of NASA and implemented by Olcott
et al. (1991a).
[0056] In Olcott's implementation of Dolgin's design, each
composite layer is comprised of multiple plies of pre-preg
composite material arranged in a series of chevron-like patterns.
Each composite layer is also comprised of several "segments" of
material where the fiber angle in a given segment is oriented in a
single direction throughout its thickness. Segments on opposite
sides of the embedded viscoelastic material have the opposite
angular orientation. At least two adjacent segments in a given
composite layer are required to form a chevron and are joined
together by staggering and overlapping the pre-preg plies in the
segment.
[0057] By tailoring the fiber angle, thickness, and segment
lengths, significant shearing in the viscoelastic layer was
observed over the entire structure, not just at the ends as in
Barrett's design (Olcott et al., 1991b; Olcott, 1992).
[0058] Olcott's research showed that the fiber orientation, segment
length, segment overlap length, material choice, and material
thickness, had to be carefully controlled to maximize damping in a
structure (Olcott, 1992). His best design, built and tested, was a
51 cm (20 inch) tube that used a fiber lay of .+-.25.degree. and a
segment length of 3.8 cm (1.5 inches). This single damping layer
tube produced almost 9% damping in the axial mode. Olcott also
experimented with the use of chevron damping patterns in the
flanges of a composite "I" beam with good success [Olcott, 1992
#19].
[0059] Pratt, et. al. [Pratt, 1997 #105] proposed several processes
for making the wavy composites contemplated by Dolgin, their use in
combination with viscoelastic materials for increased damping in
composite structures, and the manufacture and use of several
specialized wave forms.
[0060] The following publications, incorporated herein by
reference, are cited for further details on this subject.
[0061] 1. Pratt, W. F. (1998). "Damped Composite Applications and
Structures Using Wavy Composite Patterns," Patent Application
60/027,975. US & PCT.
[0062] 2. Pratt, W. F. (1999). "Patterned Fiber Composites,
Process, Characterization, and Damping Performance," Ph.D.
Dissertation. Provo, Utah, Brigham Young University, 195 pgs.
(Note: not yet publicly released as of Sept. 19, 2000).
[0063] 3. Pratt, W. F. (2000). "Method of making damped composite
structures with fiber wave patterns," U.S. Pat. No. 6,048,426. US
& PCT, Brigham Young University.
[0064] 4. Darrow, Burgess, "Reinforced Web," 1931, U.S. Pat. No.
1,800,179.
[0065] 5. Dolgin, Benjamin P., "Composite Passive Damping Struts
for Large Precision Structures," 1990, U.S. Pat. No. 5,203,435.
[0066] 6. Dolgin, Benjamin P., "Composite Struts Would Damp
Vibrations," NASA Technical Briefs, 1991, Vol. 15, Issue 4, p.
79.
[0067] 7. Hyer, M. W. (1997). "Stress Analysis of Fiber-Reinforced
Composite Materials," The McGraw-Hill Companies, Inc.
[0068] 8. Mellor, J. F. (1997). "Development and Evaluation of
Continuous Zig-zag Composite Damping Material in Constrained Layer
Damping," Masters Thesis, Provo, Utah, Brigham Young
University.
[0069] 9. Olcott, D. D., (1992). "Improved Damping in Composite
Structures Through Stress Coupling, Co-Cured Damping Layers, and
Segmented Stiffness Layers," Ph.D. Thesis, Provo, Utah, Brigham
Young University,
[0070] 10. Reinfelder, W., C. Jones, et al. (1998). "Fiber
reinforced composite spar for a rotary wing aircraft and method of
manufacture thereof", U.S. Pat. No. 5,755,558. US, Sikorsky
Aircraft Corporation.
[0071] 11. Trego, A. (1997). "Modeling of Stress Coupled Passively
Damped Composite Structures in Axial and Flexural Vibration,"
Brigham Young University, Ph.D. Thesis, Provo, Utah, Brigham Young
University.
[0072] 12. Pratt, W. F. (1998). "Damped Composite Applications and
Structures Using Wavy Composite Patterns," Patent Application
60/027,975. US & PCT.
[0073] 13. Pratt, W. F. (1999). "Patterned Fiber Composites,
Process, Characterization, and Damping Performance," Ph.D.
Dissertation. Provo, Utah, Brigham Young University, 195 pgs.
(Note: not yet publicly released as of Sept. 19, 2000).
[0074] 14. Pratt, W. F. (2000). "Method of making damped composite
structures with fiber wave patterns," U.S. Pat. No. 6,048,426. US
& PCT, Brigham Young University.
[0075] 15. Pratt, W. F. (2000). "Crossply Wavy Composite
Structures," Provisional Patent Application 60/240,645. US &
PCT.
[0076] 16. Dolgin, Benjamin P., "Composite Passive Damping Struts
for Large Precision Structures," 1990, U.S. Pat. No. 5,203,435.
[0077] 17. Dolgin, Benjamin P., "Composite Struts Would Damp
Vibrations," NASA Technical Briefs, 1991, Vol. 15, Issue 4, p.
79.
[0078] 18. Hyer, M. W. (1997). "Stress Analysis of Fiber-Reinforced
Composite Materials," The McGraw-Hill Companies, Inc.
[0079] 19. Olcott, D. D., (1992). "Improved Damping in Composite
Structures Through Stress Coupling, Co-Cured Damping Layers, and
Segmented Stiffness Layers," Ph.D. Thesis, Provo, Utah, Brigham
Young University.
[0080] 20. Cabales, Raymund S.; Kosmatka, John B.; Belknap, Frank
M., "Golf shaft for controlling passive vibrations," 1999, U.S.
Pat. No. 5,928,090.
[0081] 21. Cabales, Raymund S.; Kosmatka, John B.; Belknap, Frank
M., "Golf shaft for controlling passive vibrations," 2000, U.S.
Pat. No. 6,155,932.
[0082] 22. Pratt, William. F; Allen, Matthew; Jensen, C. Greg,
"Designing with Wavy Composites," SAMPE Technical conference, 2001,
Vol. 45, Book 1, pp 302-215.
[0083] 23. Pratt, William. F; Allen, Matthew; Skousen, Troy S.,
"Highly Damped Lightweight Wavy Composites," Air Force Technical
Report AFRL-VS-TR-2001 -tbd, 2001.
[0084] 24. Easton, James L.; Filice, Gary W.; Souders, Roger;
Teixeira, Charles, "Tubular metal ball bat internally reinforced
with fiber composite," 1994, U.S. Pat. No. 5,364,905.
[0085] 25. Lewark, Blaise A., "Reinforced baseball bat," 2000, U.S.
Pat. No. 6,036,610.
[0086] 26. Sample, Joe M., "Break resistant ball bat," 20001, U.S.
Pat. No. 6,238,309.
[0087] Pratt (reference 1) proposed the use of wavy composite
contemplated by Dolgin (references 5 and 6) as constraining layers
for a soft viscoelastic damping material in several combinations of
wavy composite, viscoelastic, and conventional materials.
Additionally, Pratt proposed the use of "wavy pre-preg for use with
or without a separate viscoelastic layer" but did not teach or
further amplify the construction or benefits. Pratt (reference 2,
page 92) proposed, constructed, and tested balanced wavy composite
crossply samples (without viscoelastic layers) for the purpose of
determining the properties of wavy composite.
[0088] Darrow (reference 4) proposed a device for obtaining a
permanent sinuous waveform in metallic wires for the production of
rubber tires but never contemplated modern fibers, resin systems
and composite structures.
[0089] Dolgin (reference 5) proposed a specialty composite
structure made from opposing chevron and sinusoidal patterned
composite lamina constraining a viscoelastic layer. In reference 6
Dolgin stated that the production of wavy sinusoidal pre-preg
should be possible but did not describe any process or apparatus.
Neither reference taught or cited any method of constructing or
using wavy or chevron patterned composites as replacements for
unidirectional pre-preg based wavy crossply laminates.
[0090] Hyer (reference 7) is a good all-around and current basic
composite book that covers the properties of composites, especially
unidirectional pre-preg based crossply laminates. Wavy composite is
not mentioned at all.
[0091] Mellor (reference 8) proposed the use of standard
bi-directional cloth in a zig-zag (chevron) pattern contemplated by
both Dolgin and Olcott as a constraining layer for viscoelastic
materials. No use of this concept as a structural material in a
wavy crossply structure was contemplated, mentioned, or taught.
[0092] Olcott (reference 9) predated Mellor and proposed,
fabricated, and tested the chevron patterns used as constraining
layers for viscoelastic damping layers contemplated by Dolgin.
Olcott did not contemplate use of wavy or chevron patterned laminae
without the use of viscoelastic layers.
[0093] Reinfelder, et al, (reference 10) discussed the construction
of a rotary wing spar for use on a helicopter. It is a good example
of the superiority of crossply laminates and is an example of an
application that could benefit from the use of wavy crossply
laminate structures.
[0094] Trego (reference 11) extended the Finite Element Analysis
model proposed by Olcott (reference 9) and built several chevron
based constrained layer damping tubes to validate the model. No
mention of using wavy composites in wavy crossply lay-ups was made
or proposed.
[0095] Crossply lay-ups, as discussed by Reinfelder, et al, and
Hyer, typically involve the use of unidirectional pre-preg with
fiber orientations designed to maximize the desired structural
properties. For example, if a tube is to be loaded in the
longitudinal or axial mode, most if not all of the unidirectional
fibers would be oriented in the longitudinal (or 0.degree.)
direction for maximum stiffness. Some small percentage of total
fibers in the tube may be oriented perpendicular to these fibers
for hoop strength, to prevent separation, or to prevent buckling,
but such fibers would not resist longitudinal loads. Such tubes are
easy to make by cutting an appropriate length of unidirectional
pre-preg from a roll and rolling the composite onto a mandrel. No
fibers (for the 0.degree. layers) are cut or interrupted. Loads are
resisted best when fibers are not cut. If cut, loads between such
fibers are transmitted through the matrix or resin and stiffness
and strength can be considerably reduced. A tube with all or mostly
0.degree. fibers would be very efficient in resisting longitudinal
loads but would not resist any significant torque or bending loads
because such loads would be resisted primarily by the shear
strength of the matrix and not by fibers.
[0096] A better design for resisting torque loads in a tube would
be to add additional layers of fibers oriented at angles to the
longitudinal axis so that the fibers would spiral around the tube.
Such fibers would provide the primary resistance to torque loads
and would provide resistance to shearing loads along the neutral
axis during bending similar to a truss like structure. To avoid
cutting the fibers (except at the ends of a tube) the
unidirectional pre-preg would have to be spirally wound on the tube
which is a concept that sounds simple, but in reality is extremely
difficult to do correctly. More typically, the unidirectional
materials are cut at an angle from a larger sheet and the
"off-axis" rectangle of material thus created is rolled on to the
tube as is done for the longitudinal fiber plies. This leaves a
series of cut fibers that spiral around the tube ending on a
discernable seam that runs the length of the tube. This represents
a potentially significant weakness in the crossply laminate. If
several such layers of opposing "off-axis" plies are used, the
normal practice is to offset the ending and beginning of such plies
so that the seams of each layer are offset. (Reinfelder, et al,
1998).
[0097] Pratt (reference 1) proposed the use of wavy composite
contemplated by Dolgin (references 5 and 6) as constraining layers
for a soft viscoelastic damping material in several combinations of
wavy composite, viscoelastic, and conventional materials.
Additionally, Pratt proposed the use of "wavy pre-preg for use with
or without a separate viscoelastic layer" but did not teach or
further amplify the construction or benefits. Pratt (reference 2,
page 92) proposed, constructed, and tested balanced wavy composite
crossply samples (without viscoelastic layers) for the purpose of
determining the properties of wavy composite. Pratt (reference 15)
revealed and taught the advantages of using wavy crossply composite
laminates in structures to provide improved structural properties,
especially resistance to torque, bending, and axial loads.
[0098] Dolgin (reference 5) proposed a specialty composite
structure made from opposing chevron and sinusoidal patterned
composite lamina constraining a viscoelastic layer. In reference 6
Dolgin stated that the production of wavy sinusoidal pre-preg
should be possible but did not describe any process or apparatus.
Neither reference taught or cited any method of constructing or
using wavy or chevron patterned composites as replacements for
unidirectional pre-preg based wavy crossply laminates, nor the use
of combinations of wavy crossply laminates in conjunction with
Dolgin's (references 5 and 6) wavy damping methods.
[0099] Hyer (reference 7) is a good all-around and current basic
composite book that covers the properties of composites, especially
unidirectional pre-preg based crossply laminates. Wavy composite is
not mentioned at all.
[0100] Olcott (reference 9) proposed, fabricated, and tested the
chevron patterns used as constraining layers for viscoelastic
damping layers contemplated by Dolgin. Olcott did not contemplate
use of wavy or chevron patterned laminae without the use of
viscoelastic layers.
[0101] Crossply lay-ups, as discussed by Reinfelder, et al, and
Hyer, typically involve the use of unidirectional pre-preg with
fiber orientations designed to maximize the desired structural
properties.
[0102] Cabales, et.al. in references 20 and 21 propose the
construction of golf club shafts using concepts invented by Dolgin
(reference 5) and techniques proposed by Olcott (reference 19). The
basic design contemplated by Cabales, et.al. relied on two load
bearing laminates on the inside and outside of the shaft, placing a
"damping device" in the space between these laminates using
viscoelastic and "V" or "herringbone" fiber patterns proposed by
Olcott (reference 19). These V or herringbone patterns are
constructed from strips of unidirectional material that is cut on
an angle and then joined by a series of overlapping butt joints
(reference 19). Such methods are impractical in the extreme
requiring an estimated 70 separate pieces of composite for one
"damping device" that must be hand assembled for one shaft.
Additionally, because of the inherent weakness of the overlapped
butt joints, a minimum of four layers must be used for any V or
herringbone damping layer (reference 19). Such a shaft, if it can
be accurately assembled at all, would weigh at least 50% more than
a steel golf shaft and would therefore be unacceptable to the
public. In short, such a design is impractical if not
impossible.
[0103] Finally, Cabales, et.al. did not contemplate the use of wavy
or sinuous fiber reinforced materials either in their claims or the
disclosure of the invention but instead specifically cited Olcott's
"V" or herringbone method in the claims. Additionally, Cabales,
et.al. state that the use of precisely controlled regions or
lengths of viscoelastic material application are required for the
efficient damping of higher vibration modes of the shaft. More
recent research in references 22 and 23 show that peak damping
frequency and damping magnitude at any given frequency are only
functions of the wave period and will dampen all modes based on the
characteristics of the material. Since Olcott did not use methods
of testing that produce an accurate characterization or material
nomograph of the "V", herringbone, or "zig-zag" laminate design,
such an understanding of the material's true properties was never
accomplished and Olcott and others were left to erroneously
conclude that damping performance was a function of the length of
the damping regions and not a function of the period of the
pattern. Finally, Cabales et.al. indicate that the "V" or
"herringbone", or "zig-zag" patterns in the layers (items 10 &
12 in FIGS. 1-3, and items 310 & 312 in FIGS. 4-5) are joined
along their length to the structural layers of the shaft (items 16
& 18 FIGS. 1-5) which defeats the differential shearing action
necessary for damping. This means that these layers would be
essentially non-functional and would contribute little if anything
to the damping performance of the shaft. As shown by Pratt, et.al.
in References 1-15,22, and 23 wavy damping layers must be free to
shear differentially to be effective. The same is true for the "V"
or "herringbone", or "zig-zag" patterns contemplated by Cabales,
et.al.
[0104] In reference 15, Pratt revealed an enhanced method of making
composite structures with crossply characteristics but constructed
entirely from wavy composite. Pratt showed how wavy composite
pre-preg can be used to create virtually seamless crossply-like
laminates with little or no interruption of fibers. Such a laminate
displays the properties of both unidirectional and crossply
characteristics in that it can efficiently resist both axial and
transverse shearing loads.
[0105] Application of Dolgin's sinuous or wavy composite damping
concept shown in FIG. 1 on a base structure made either with
conventional composite materials (unidirectional, woven cloth),
isotropic materials (steel, aluminum, etc.), or wavy crossply
materials (FIG. 25, Item 7), provides for an efficient,
lightweight, and highly damped golf club (FIG. 32) as one example.
Such a golf shaft requires only 10 separate pieces of material
including two viscoelastic layers, can be assembled in a few
minutes and is capable of automated assembly, and is at least 25%
lighter than a typical steel shaft of the same stiffness. Therefore
there remains a need for a practical method of making golf club
shafts (and other devices) using Dolgin's sinuous or wavy composite
damping concept that has heretofore not been contemplated by
others.
[0106] Easton, et.al. in Reference 24 describes an internally
reinforced metal ball bat wherein the internal reinforcing material
is comprised of bi-directional composite cloth layers applied to
the interior of the barrel. The advantages cited were
reinforcement, added strength and quicker shape recovery after
impact. Lewark in Reference 25 reinforced a wooden bat in the
handle region with bi-directional composite cloth layers to provide
for breakage resistance. Sample in Reference 26 provided
reinforcement to the handle of a wooden bat with straight fibers
oriented along the length of the handle. None of these references
mention wavy composite nor a method for reinforcing the handle of a
bat with crossply wavy composite nor adding damping to the body of
the bat using wavy composite damping layers. This is true for
wooden bats, hollow metal bats, composite bats, or hybrid designs
combining wood, and/or metal, and/or composite.
GENERAL DESCRIPTION
[0107] The composite structures of this invention may take a
variety of forms, including plates with or without stiffeners,
beams, curved surfaces, or irregular shapes. In any event, each
structure has at least one CWC laminate and at least one
viscoelastic layer. The viscoelastic layer need not be a separate
material or layer but may be formed by a thin boundary layer of
matrix from the composite during curing; such a CWC material would
of course have a special matrix.
[0108] Damping is induced in the structure primarily by the
differential shearing of the viscoelastic layer by the CWC
laminate. This shearing induces elongation of the long chain
polymers in the viscoelastic which in turn generates heat, causing
energy loss in the structure. This energy loss accounts for the
primary source of damping in the structure.
[0109] There remains a need for a composite structure capable of
diverse configuration with improved damping characteristics and
which avoids the limitations of the structural approaches
heretofore suggested for use with composite materials.
SUMMARY OF THE INVENTION
[0110] The terminology CWC (continuous wave composite) will be used
to define any fiber-matrix combination having at least one fiber
without a break (or interruption) and having a pattern which can be
defined by a mathematical algorithm. Typically, such curves have
G.sup.1 geometric continuity. A fourier series expansion is a
mathematical algorithm which can, in general, be used to define
nearly any desired shape such as a pseudo random, square wave,
straight line, triangular wave or any of the shapes shown in FIGS.
1-6.
[0111] The terminology CWCV (continuous wave composite
viscoelastic) will be used to define a composite structure which
uses at least one layer of CWC material having viscoelastic
properties (or `anisotropic viscoelastic`); or at least one layer
of CWC material combined with at least one layer of viscoelastic
material either in a sandwich construction or adjacent
construction.
[0112] A CWCV is defined by specifying the angle of the fiber lay
along the composite layers (e.g. the orientation angles of the
fiber with respect to the loading direction), the thickness of the
composite layers, and the number of composite and viscoelastic
layers in the structure.
[0113] The lay of fiber in a CWCV composite layer is varied
continuously in a periodic wavelike form. A simple sinusoid wave
form may be used, however, other wave forms which may or may not be
periodic may also be used. It is also envisioned to employ an
optimal wave form for damping particular vibration frequencies at
particular locations of a structure.
[0114] The ends of a CWCV structure according to the present
invention may be restrained without significantly reducing the
overall damping properties of the structure. There results a
structural element possessing high axial stiffness and low weight.
The structural elements of this invention offer markedly superior
damping capabilities but are nevertheless useable with simple
attachment fixtures and methods.
[0115] Damping is induced in the structure primarily by the
differential shearing of the viscoelastic layer by the CWC
laminate. This shearing induces elongation of the long chain
polymers in the viscoelastic which in turn generates heat, causing
energy loss in the structure. This energy loss accounts for the
primary source of damping in the structure.
[0116] The invention also includes fiber patterns which change
their wavelength and/or waveform along the loading direction. The
inventor has discovered that for a given frequency and temperature
many viscoelastic adhesives will require an optimal wavelength to
maximize damping in the structure. While a structure with a
constant wavelength can be optimized for a given frequency and/or
temperature, placement of a changing wavelength or waveform can
optimize a structure for a broader range of frequencies and/or
temperatures.
[0117] Stress coupled composite structures having one fiber angle
at any given point along the loading direction are not able to
withstand as much stress as one having multiple angles contained
within a matrix. This is because failures occur in composite
materials starting at areas of maximum in-plane shear stress in the
composite layer, and propagate in the matrix material along the
fiber direction.
[0118] The present invention further envisions complex fiber
patterns, such as those shown in FIGS. 2-4, generated by an
algorithm for optimizing pattern and/or shape, wave period, wave
amplitude, structural stiffness, and structural damping. Using
techniques similar to electronic signal processing, wave forms can
be generated algorithmically which vary wave patterns by mixing two
or more algorithmically defined waves with one or more differences
in shape, period, amplitude, etc. For example:
[0119] A period modulated wave shape where two or more waves of
differing period with or without the same amplitude, combined into
one composite shape. This could be used to optimize damping and/or
stiffness in complex structures where modal vibration and/or
forcing functions require special design considerations.
[0120] An amplitude modulated wave shape could be used to modify
stiffness and damping properties at varying positions in the
structure.
[0121] A wave shape composed of two or more similar or dissimilar
wave forms of different periods such that the combined wave form
shows a mixed characteristic of all such combined waves. This would
allow tailoring of structural properties for multiple modes and
forcing functions.
[0122] A bessel based wave shape, a fourier series driven shape,
sawtooth, trapezoidal, square wave, and modulated (by other similar
or dissimilar wave forms) patterns.
[0123] Optimized patterns not necessarily algorithmically driven
which are tailored by an optimization program to provide special
structural response characteristics.
[0124] Random and/or neo-random patterns, and patterns which are a
mixture of random or neo-random and periodic wave shapes.
[0125] A structure which uses conventional straight fiber
composites to constrain an anisotropic viscoelastic material.
[0126] It has been shown that higher frequency resonance or forcing
functions require shorter wave periods for optimization of damping
in CWCV structures. See, for example, the following publications
incorporated herein by reference:
[0127] 1. Pratt, W. F., Rotz, C. A. and Jensen, C. G. 1996
"Improved Damping and Stiffness in Composite Structures Using
Geometric Fiber Wave Patterns," Proceedings of the ASME Noise
Control and Acoustics Division, Vol. NCA 23-2, pp. 37-43.
[0128] 2. Pratt, W. F., Rotz, C. A., and Jensen, C. G., 1996, "On
the Use of Continuous Wave Composite Structures in Stress Coupled
Interlaminar Damping," Advanced Materials: Development,
Characterization Processing, and Mechanical Behavior Book of
Abstracts, Vol. MD 74, pp. 63-64.
[0129] 3. Pratt, W. F., Rotz, C. A., and Jensen, C. G., 1996, "On
the Use of Continuous Wave-like Geometric Fiber Patterns in
Composite Structures to Improve Structural Damping," Proceedings of
the ASME Aerospace Division, Vol. AD 52, pp. 415-433.
[0130] In summary, a continuous wave fiber composite material
according to the present invention may include one or more
anisotropic composite layers with or without viscoelastic
properties, and therefore respectively used without or with a
separate viscoelastic layer. Of course, one may also utilize
composite layers with viscoelastic properties (i.e., the
viscoelastic material may comprise all or part of the matrix
material binding the fibers) and separate viscoelastic layers as
well. Features of the pattern of reinforcing fibers may
include:
[0131] A constant wavelength and/or waveform (see FIG. 1);
[0132] A wavelength and/or waveform that varies along the length of
the structure (see FIG. 2);
[0133] A pattern in one CWC laminae having multiple wavelengths
and/or waveforms (see FIG. 4); and
[0134] Multiple combinations of CWC laminae and viscoelastic layers
using one or more of the above features (see FIGS. 3 and 5).
[0135] In a further aspect of the present invention, an apparatus
and method for manufacturing composite materials such as those
described above are also envisioned.
[0136] Generally, characteristics of the processes and machines
include:
[0137] laying the fiber(s) in a controlled pattern which can be
periodic or non-periodic;
[0138] producing a fiber reinforced composite material consisting
of matrices containing continuous fibers. The matrices can consist
of conventional polymers, viscoelastic materials, or more exotic
materials including (but not limited to) metal, ceramic, or
combinations of materials. The fibers can consist of unidirectional
tow or woven mats.
[0139] The present invention is directed to the use of wavy
composite and damping materials in basic structural components
typically representing parts of panels, plates, and beams.
[0140] The invention is also directed to a CWC (continuous wave
composite) which forms a continuously wavy pre-preg for use with or
without a separate viscoelastic layer.
[0141] In both the CWCV and CWC structures, the wavy characteristic
of the fiber is optimally varied in at least one of a period,
amplitude or shape characteristic.
[0142] In accordance with another aspect of the invention, there is
provided a fiber reinforced viscoelastic tape with may be used in
many diverse applications.
[0143] The invention is also directed to the use of basic wavy
composite damping structural components to form specific practical
devices and applications.
[0144] The present invention is directed to "continuous wave
composite viscoelastic" (CWCV) structures, as well as the methods
and apparatus of manufacturing them.
[0145] The composite structures of this invention may take a
variety of forms, including tubes, plates, beams or other regular
or irregular shapes. In any event, a typical structure will at a
minimum include a first stiffness layer or matrix, a damping
material, and a second stiffness layer or matrix. Each stiffness
layer or matrix will include at least one reinforcing fiber and
will be at least several thousandths of an inch thick. Layers with
multiple plies and of much greater thickness; e.g. several inches,
are envisioned. The fibers of a multi-ply layer may be of similar
or dissimilar orientation. The damping material may be of any
appropriate thickness, depending upon the application involved, as
well as the properties of the damping material selected. The
damping material may comprise another layer interposed between the
stiffness layers, or may be incorporated into the stiffness layer.
Typically, the damping material will be as thin as is practical, to
avoid adding excess weight to the structure. It is not unusual,
however for a layer of damping material to exceed in thickness the
total thickness of the stiffness layers. The stiffness layers may
be constructed of any of the reinforcing fibers and matrix
materials which would otherwise be appropriate for a particular
application. The damping material will ordinarily be selected to
provide optimum damping loss at the temperatures and vibrational
frequencies expected to be encountered by the composite
structure.
[0146] The present invention is directed to an improved composite
structure and method for manufacturing the same from wavy fiber
pre-preg materials. Generally, characteristics of the structure and
methods include:
[0147] Two or more wavy laminae used in opposing patterns or offset
patterns in a composite structure, where the laminate properties
created have variable crossply characteristic.
[0148] Laminate properties that can be tailored by the stacking
sequence, waveform, offset, axis orientation, and material
used.
[0149] Wavy crossply structures that can be laid down by tape
laying machines and apparatus with as little as one axis of
control.
[0150] Wavy crossply structures that minimize the interruption of
fibers thereby making the laminate stronger and less prone to
failure.
[0151] Wavy composite pre-preg can be used to create virtually
seamless crossply-like laminates with little or no interruption of
fibers. This is simply accomplished by combining two or more wavy
composite plies using opposing waveforms in its simplest form, or
by using combinations of opposing and offset wavy composite
waveforms to form the laminate. Such a laminate displays the
properties of both unidirectional and crossply characteristics in
that it can efficiently resist both axial and transverse shearing
loads.
[0152] The fact that such a structure, which has fibers oriented in
multiple directions, can be laid down with standard automation
equipment (with as little as one axis of control) makes the
structure and method economical. This is in contrast to laminates
and methods used to make conventional unidirectional pre-preg based
crossply laminates which cannot readily be automated. Additionally,
experience has shown that wavy pre-preg can be more easily draped
over contoured surfaces and tooling, further easing
fabrication.
[0153] Finally, there is a finite maximum width to pre-preg
(typically 60 inches maximum) which often causes laminators to have
to splice and overlap sheets of unidirectional pre-preg together to
form large laminae. This is especially true for off-axis
unidirectional laminae. This introduces seams which often represent
a significant weakness in the laminate (see FIG. 27, items 12-14).
Wavy composite can be easily spliced together across the width
without the need to interrupt the edge fibers (see FIG. 27, item 1
and 15). Since the present invention discloses how wavy composite
laminae can be combined to produce crossply laminate structures, it
is now possible to create such structures with a minimum of
interruption of fiber continuity and without overlapping seams. In
fact, wavy crossply tubes have been made that exhibit no
discernable seam, have no interruption of fibers (except naturally
at the ends of the tubes), and which display classic crossply
laminate characteristics.
[0154] The present invention also relates to the use of wavy
composite and unidirectional composite in crossply lay-ups in the
generalized fabrication of tubes, wing spars, rotary wing spars,
and similar structures.
[0155] The present invention is directed to an improved composite
structure and method for manufacturing the same from wavy fiber
pre-preg materials. Generally, characteristics of the structure and
methods include:
[0156] Wavy composite structures with high damping consisting of at
least one wavy composite layer combined with at least one
viscoelastic damping layer.
[0157] Two or more wavy laminae used in opposing patterns or offset
patterns in a composite structure, where the laminate properties
created have variable crossply characteristic that can be tailored
by the stacking sequence, waveform, offset, axis orientation, and
material used.
[0158] Wavy crossply structures that can be laid down by tape
laying machines and apparatus with as little as one axis of
control.
[0159] Wavy crossply structures that minimize the interruption of
fibers thereby making the laminate stronger and less prone to
failure.
[0160] The present invention also relates to the use of wavy
composite and unidirectional composite in crossply lay-ups in the
fabrication of tubes, golf club shafts, torque tubes, drive shafts,
fishing rods, baseball bats, and similar structures.
[0161] The present invention also relates to the use of wavy
composite and unidirectional composite in crossply lay-ups using
interrupted viscoelastic methods as shown in Figures in the
fabrication of tubes, golf club shafts, torque tubes, drive shafts,
fishing rods, baseball bats, and similar structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0162] The accompanying drawings (FIGS. 1-12), were incorporated in
the original patent and constitute a part of the specifications and
preferred embodiment for that invention. They are presented here as
reference and further explanation for FIGS. 13-22.
[0163] FIG. 1 is an exploded perspective view of a composite
material according to a generalized embodiment of the present
invention. It is an exploded perspective view of the Dolgin
invention, reference 5.
[0164] FIG. 2 is an exploded perspective view of a composite
material according to an alternate embodiment of the present
invention.
[0165] FIG. 3 is an exploded perspective view of a composite
material according to another alternate embodiment of the present
invention.
[0166] FIG. 4 is a perspective view illustrating two examples of
matrices according to yet another embodiment of the present
invention.
[0167] FIG. 5 is an exploded perspective view of a composite
material according to yet another alternate embodiment of the
present invention.
[0168] FIGS. 6A, 6B and 6C are exploded perspective view of a
composite material and damping layer coupled to an isotropic layer
in accordance with another embodiment of the invention.
[0169] FIG. 7 is a schematic illustration of an apparatus according
to the present invention for manufacturing a composite
material.
[0170] FIGS. 8A and 8B are illustrations of bent fibers showing how
the volume fraction is enhances with the use of bending.
[0171] FIG. 9 is a schematic illustration of an alternate apparatus
according to the present invention for manufacturing a composite
material.
[0172] FIG. 10 is a schematic illustration of another alternate
apparatus according to the represent invention for manufacturing a
composite material.
[0173] FIG. 11 is a schematic illustration of yet another alternate
apparatus according to the present invention for manufacturing a
composite material.
[0174] FIG. 12 is a schematic illustration of still another
alternate apparatus according to the present invention for
manufacturing a composite material.
[0175] The accompanying drawings (FIGS. 13-21), which are
incorporated in and constitute a part of the specification,
illustrate preferred embodiments of the invention, and serve to
explain the principles of the invention.
[0176] FIG. 13 shows a perspective view and series of end views of
a CWCV plate, according to an alternate embodiment of the present
invention. It is the most basic CWCV laminate building block
consisting of opposing waves constraining a viscoelastic layer as
shown in FIG. 1.
[0177] FIG. 14 shows a perspective view and a series of end views
of CWCV plates with damped CWCV hat-stiffeners, according to an
alternate embodiment of the present invention.
[0178] FIG. 15 shows a perspective view and a series of end views
of CWCV structures with damped CWCV laminates and I-beam,
C-channel, Z-channel stiffeners, according to an alternate
embodiment of the present invention.
[0179] FIG. 16 shows a perspective view and a series of end views
of CWCV structures with damped CWCV laminates and core materials
used to give the structure shape, according to an alternate
embodiment of the present invention.
[0180] FIG. 17 shows end views of aerodynamically shaped CWCV
structures with damped CWCV laminates and CWCV hat-stiffeners,
and/or I beam and/or channel stiffeners, according to an
alternative embodiment of the present invention.
[0181] FIG. 18 shows a perspective view of a CWCV plate and a
series of end views of damped CWCV laminates and CWCV structures
with CWCV hat-stiffeners or I-beam stiffeners, according to an
alternative embodiment of the present invention.
[0182] FIG. 19 shows a perspective view and end views of damped
CWCV materials used to build a snow ski, water ski, snow board,
etc. with damped CWCV laminates on one side, and common core
materials, metal edgings, and surface materials, to enhance damping
and dynamic properties, according to an alternative embodiment of
the present invention.
[0183] FIG. 20 shows a perspective view and end views of damped
CWCV materials used to build a snow ski, water ski, snow board,
etc. with damped CWCV laminates sandwiching a common core material,
in addition to metal edgings and surface materials, to enhance
damping and dynamic properties, according to an alternative
embodiment of the present invention.
[0184] FIG. 21 shows a perspective view and end views of damped
CWCV materials used to build a snow ski, water ski, snow board,
etc. with damped CWCV laminates wrapped around a common core
material, in addition to metal edgings and surface materials, to
enhance damping and dynamic properties, according to an alternative
embodiment of the present invention.
[0185] FIG. 22 shows a perspective view and a series of cutaway
views of CWCV tubular components with damped CWCV laminates,
according to a generalized embodiment of the present invention.
[0186] FIG. 23 is an exploded perspective view of a balanced wavy
crossply lay-up used to perform stiffness and strength tests on
wavy composite material according to reference 2.
[0187] FIG. 24 is an exploded perspective and corresponding side
view of a wavy crossply layup with a unidirectional ply interposed
for the purpose of improving laminate properties according to a
generalized embodiment of the present invention.
[0188] FIG. 25 is a top-down side view of different wavy crossply
lay-ups for the purpose of improving laminate properties according
to a generalized embodiment of the present invention.
[0189] FIG. 26 is a top-down side view of different unidirectional
crossply lay-ups for the purpose of comparison to the present
invention.
[0190] FIG. 27 is an illustration of the advantages of joining
adjacent wavy composite plies to make wider laminae compared to
typical methods used to join adjacent off-axis unidirectional
materials to create wider laminae.
[0191] FIG. 28 illustrates the ease with which wavy composites can
be used to construct efficient crossply-like layups compared to
unidirectional ply methods.
[0192] FIG. 29 is an example of a using wavy composite offset by an
angle with respect to a reference axis, with improved laminate
properties according to a generalized embodiment of the present
invention.
[0193] FIG. 30 is an exploded perspective view of one concept of
the present invention which uses the basic structure of the Dolgin
concept (reference 5), augmented by the addition of unidirectional
plies to the wavy constraining layers for the purpose of increasing
stiffness, according to a generalized embodiment of the present
invention.
[0194] FIG. 31 is a perspective view of one concept of the present
invention which uses the basic structure of the Dolgin concept
(reference 5), augmented by the addition of unidirectional plies to
the wavy constraining layers for the purpose of increasing
strength, were the constrained viscoelastic layer is discontinuous
for the purpose of increasing strength, according to a generalized
embodiment of the present invention.
[0195] FIG. 32 shows the construction of a typical golf club shaft
with damping layers and wavy composite used to provide superior
properties, according to a generalized embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0196] The CWCV shown in FIGS. 13-22 show a fiber pattern that is
generally sinusoidal with a constant wave form, period, etc. Since
the damping properties are frequency and temperature dependent, and
since the selection of an optimal wave shape can be influenced by
the desired structural response, a non-periodic, non-sinusoidal
wave shape may be the preferred optimal CWC. There are other
variables such as selection of materials, relative thickness of
laminates, etc., not shown or discussed below that are important
for correct design in addition to selection of wave shape, etc. The
selection of these details will be necessarily customized for
different designs and will be obvious to one skilled in the art.
The discussions below are intended to illuminate the general design
of CWCV that will be common to most CWCV structures and that will
result in optimal strength, damping and stiffness. Therefore, wave
shapes, relative sizes and thickness of component laminates, etc.,
will require analysis by the designer based on the desired
structural response. The representations of these design parameters
in FIGS. 13 through 22 are exemplary only.
Basic CWCV Plate
[0197] The CWCV plate is the most basic unit built with these new
materials. It can be shaped and bent to make stiffener building
blocks. CWCV plates, stiffeners and cores cab be combined in any
combination to form intermediate structural members. The
intermediate structural members can be combined with additional
CWCV building blocks to form larger structures.
[0198] FIG. 13a is a plate with two layers of CWC and an
intermediate layer of viscoelastic and represents any combination
of waveforms shown in FIGS. 1-5. The CWC layers may be made with
bi-directional cloth as well as unidirectional fibers.
[0199] In FIG. 13a the plate (1) is comprised of two CWC laminates
of opposing wave forms (4 & 5) constraining a viscoelastic
layer (2). In FIG. 13a-1 two of the laminates shown in FIG. 13a are
combined without a viscoelastic layer in between so that the CWC
laminates which are bonded together without the benefit of a
viscoelastic layer are of a matched waveform (Item 5). The laminate
representation is (4)/(2)/(5)/.sub.2(2)/(- 4) where the number in
parenthesis represents the material type as discussed above, and
the subscript denotes the number of laminates of the indicated
type. It has been found that balancing a multi-laminate CWCV plate
in this manner gives the most efficient damping and strength
performance. Two or more plates as shown in FIG. 13a-1 can be
combined to form thicker laminates as shown in FIG. 13a-2 (6).
[0200] The CWCV plate shown in FIG. 13a has its primary damping
properties along the direction of the fiber pattern. The transverse
damping properties are not as pronounced. FIG. 13b is a way of
combining two CWCV laminates oriented at different angles with
respect to each other and bonded by a viscoelastic layer. This
allows the engineer and designer to design structures with
efficient damping properties in more than one direction. The
example shown in FIG. 13b shows two CWCV plates oriented at
90.degree. with respect to each other. Items 4, 2, and 5 from FIG.
13a are combined with an additional viscoelastic layer (2) and
another laminate (4a, 2, 5a) which are oriented in a different
direction.
[0201] The laminate in FIG. 13b, provides efficient damping in more
than one direction but represents an unbalanced ply laminate. The
plate shown in FIG. 13c is a way of combining four CWCV plates with
the top and bottom plates oriented in the same direction and the
intermediate two plates oriented in another direction. Of course it
is possible to combine multiple plates as shown in FIG. 13a, 13a-1
and 13a-2 in various directions to provide efficient damping and
strength properties according to the design goals of the
engineer.
[0202] FIG. 13d shows a CWC laminate (4) combined with viscoelastic
materials (2) and conventional materials (7) which can be composed
of traditional cross-ply laminates, isotropic materials, plastics,
or other materials according to the design criteria of the
engineer. In this case the conventional materials are shown
constraining a central CWC laminate.
[0203] FIG. 13e shows the same basic structure of 13d but instead
of a single CWC laminate, the conventional material (7) constrains
an opposing CWCV plate (such as shown in FIG. 13a). The designer is
not limited to a single CWC laminate or a single CWCV plate but may
combine any of the structures shown in 13a, 13a-1, 13a-2, 13b, and
13c to produce a CWCV plate with tailored properties of stiffness
and damping in one or multiple directions.
[0204] FIGS. 13f and 13g show the same concepts as FIG. 13d and 13e
with one conventional material constraining layer (7) removed. The
comments for 13d and 13e apply equally to these figures. It is
therefore possible to produce a CWCV plate with tailored properties
of stiffness and damping in one or multiple directions.
[0205] FIG. 13h shows a single conventional material (7)
constrained on two sides by a CWCV plate. As shown in FIG. 13h the
constraining CWC laminates (4 or 5) do not have to be opposing
waveforms, but may if the designer chooses. FIG. 13i shows the same
basic structure as FIG. 13h only with multiple CWCV plates.
[0206] In summary, it is possible for the designer to combine
multiple layers of CWC laminates, viscoelastic materials, and
conventional materials in any number of configurations according to
the design criteria of the engineer. The examples of FIG. 13 are
for illustrative purposes and other combinations will be obvious to
one skilled in the art.
CWCV Stiffener Building Blocks
[0207] According to one aspect of the invention, a CWCV plate is
bent to form any of the other building blocks all of which are
termed "stiffeners". There are four basic shapes of a stiffener
building block including the hat-stiffener, the I-beam, the
C-channel, and the Z-channel. The terminology "hat-stiffener" will
mean any channel shaped stiffener commonly used on lightweight
structures. Generally they are "U" shaped in cross section but they
can be any cross sectional shape such as semi-circle, "V" shaped,
three sided square, etc.
[0208] The CWCV hat-stiffener is shown as Item 1 in FIG. 14 and is
a basic building block for intermediate structural members and
larger structures. For example, it can be used in combination with
CWCV or conventional material plates to form a beam (for short
widths) or part of a panel (for greater widths). The CWCV
plate-hat-stiffener combination is an intermediate structural
building block for several other larger structures such as panels,
beams, curved surfaces, aerodynamic surfaces, rotor blades,
propellers, skis, snow boards, any monocoque structure, and many
practical structural members.
[0209] As shown in FIG. 14a (perspective view) a generalized
hat-stiffened panel would consist of a hat-stiffener (1) shown with
a (for example) sinusoidal wave form, (2) a structural laminate or
a CWCV laminate (no wave form shown), and (3) a second structural
laminate or a CWCV laminate (no wave form shown), or, a special
surface treatment or material.
[0210] The composition of the hat-stiffener (FIG. 14a, Item 1)
could include any one of the CWCV plates shown in FIG. 13. The
laminates of FIG. 14a (2) and (3) could consist of one or more of
the following: a) one or more opposing CWCV plates (from FIG. 13),
and b) a conventional structural material such as an isotropic
metal, a conventional composite laminate, or any other suitable
structural material.
[0211] FIGS. 14b through 14e show end views of only a few of the
possible combinations of CWCV hat-stiffeners, conventional
materials, CWCV plates, and viscoelastic materials (not shown to
scale), and are meant to serve as examples for the structure shown
in FIG. 14a.
[0212] In FIGS. 14b and 14e the hat-stiffener (1) consists of three
laminates and two damping layers (shown shaded). In one embodiment
all three laminates would consist of CWC laminates (4) & (5),
and would constrain two viscoelastic or anisotropic viscoelastic
damping layers (6). Two of the CWC laminates would be of one
pattern (4) on the inner and outer surfaces of the hat-stiffener,
with an opposing CWC laminate (5) (a laminate having the same basic
pattern of (4) but with a 180.degree. phase shift), in the middle.
(Figures are not drawn to scale.) An alternative embodiment would
have the three laminates consist of one each of a CWC laminate, an
opposing CWC laminate, and a conventional laminate or other
material, constraining two viscoelastic or anisotropic viscoelastic
damping layers (6). The three structural laminates are joined
together at the "feet" for good bonding and structural purposes,
the damping material being omitted in the region of the feet for
this purpose. It is not necessary to configure the damping layers
as shown (e.g. in an inverted "U" shape, on top and sides) but the
damping layer may be on the top only, on the side only, or
eliminated altogether, depending on the requirements of the
designer. These examples were given using more than one
viscoelastic layer and CWC laminate; of course it is possible to
use any number of CWC laminates, viscoelastic layers, or
conventional material layers, in any combination, to accomplish the
design goals.
[0213] The laminate (2) of FIG. 14a is shown as item (7) in FIG.
14b, could be composed of a conventional composite or other
structural material, and would thus represent the main load bearing
member in the plate. As shown, the feet of the hat-stiffener are
joined directly to the load bearing member (7) promoting strength
and good bonding. The laminate (3) of FIG. 14a is shown as Items
(4), (5), & (6) in FIG. 14b, and consists of two laminates and
two damping layers (shown shaded). In one embodiment both laminates
would consist of wavy pattern CWC laminates (4) & (5), and
would constrain two viscoelastic or anisotropic viscoelastic
damping layers (6). One of the CWC laminates would be of one
pattern (4), with an opposing CWC laminate (5). An alternative
embodiment would have the two laminates consist of a CWC laminate,
and a conventional laminate or other material, constraining two
viscoelastic or anisotropic viscoelastic damping layers (6). Only
two laminates are shown in FIG. 14b but it is possible to have any
number of alternating layers of opposing CWC laminates,
viscoelastic or anisotropic viscoelastic damping layers, and
conventional composites, according to the design criteria of the
engineer.
[0214] The laminate (2) & (3) of FIG. 14a is shown as items
(4), (5), & (6) in FIG. 14c and 14d consists of multiple
laminates and damping layers (shown shaded). In one embodiment the
laminates would consist of multiple wavy pattern CWC laminates (4)
& (5), and would constrain multiple viscoelastic or anisotropic
viscoelastic damping layers (6). Some of the CWC laminates would be
of one pattern (4), with opposing CWC laminates (5). An alternative
embodiment would have some of the laminates consist of CWC
laminates, with some of conventional laminate or other material,
constraining the viscoelastic or anisotropic viscoelastic damping
layers (6). It has been determined that the structure of FIG. 14c
provides the most efficient and lightweight balanced hat-stiffened
panel since it relies on the balanced laminate of FIG. 13b. Instead
of a flexible plate as shown in FIG. 13b, the two CWCV plates are
split, one becoming a hat-stiffener. It is possible to add an
additional plate where the two plates split to form the
hat-stiffener, so that the final cross section retains a uniform
thickness and laminate structure. The designer is not limited to
the use of only two plates. The "plate" makeup may include any of
the possible combinations discussed for FIG. 13, according to the
design criteria of the engineer. Other combinations will be obvious
to one skilled in the art.
[0215] The laminate (2) of FIG. 14a is shown as items (4), (5),
& (6) in FIG. 14d, and consists of multiple laminates and
damping layers (shown shaded). In one embodiment the laminates
would consist of opposing wavy pattern CWC laminates (4) & (5),
and would constrain viscoelastic or anisotropic viscoelastic
damping layers (6). An alternative embodiment would have the some
of the laminates consist of opposing CWC laminates, some
conventional laminates or other materials, all constraining the one
or more viscoelastic or anisotropic viscoelastic damping layers
(6). It is possible to have any number of alternating layers of
opposing CWC laminates, viscoelastic or anisotropic viscoelastic
damping layers, and conventional composites, according to the
design criteria of the engineer. The laminate (3) of FIG. 14a is
shown as item (7) in FIG. 14d, could be composed of a conventional
composite or other structural material, and would thus represent
the main load bearing member in the plate.
[0216] FIG. 14 shows only a few of the design possibilities of the
use of CWCV hat-stiffeners, CWCV plates, viscoelastic damping
materials, mixed (if desired) with conventional composite or other
materials. Other configurations will be obvious to one skilled in
the art.
I-beam, C-channel, Z-channel Building Blocks
[0217] The CWCV I-beam stiffener is shown as Item 1 in FIG. 15 and
is a basic building block for intermediate structural members and
larger structures. For example, it can be used in combination with
CWCV or conventional material plates to form a beam (for short
widths) or part of a panel (for greater widths). The CWCV
plate-I-beam stiffener combination is an intermediate structural
building block for several other larger structures.
[0218] As shown in FIG. 15a (perspective view) a CWCV I-beam
stiffener (1) would be combined with a structural laminate or a
CWCV plate (3) shown with a (for example) sinusoidal wave form, and
a second structural laminate or a CWCV plate (2) (no wave form
shown), or, a special surface treatment or material.
[0219] The I-beam stiffener (1) could consist of one or more of the
following: a) a conventional composite laminate, conventional
structural material such as an isotropic metal, or any other
suitable material, and/or b) one or more opposing CWC laminates
with one or more constrained damping layers of viscoelastic
material.
[0220] The flanges (2 & 3) could consist of one or more of the
following: a) one or more opposing CWC laminates constraining one
or more damping layers of viscoelastic material, and/or b) a
combination of CWC laminates, viscoelastic or anisotropic
viscoelastic damping layers, and conventional composites or other
suitable structural material.
[0221] FIGS. 15b through 15f show end views of only a few of the
possible combinations of CWCV stiffeners, conventional materials,
and CWCV.
[0222] FIG. 15b shows one example of a CWCV I-beam stiffener
combined with two CWCV plates (flanges). Any of the CWCV plates
shown in FIG. 13 could be combined to form the basic I-beam shown
in FIG. 15b.
[0223] FIG. 15c shows one example of a CWCV C-channel stiffener
combined with two CWCV plates (flanges). Any of the CWCV plates
shown in FIG. 13 could be combined to form the intermediate
structure shown in FIG. 15c.
[0224] FIG. 15d shows one example of a CWCV Z-channel stiffener
combined with two CWCV plates (flanges). Any of the CWCV plates
shown in FIG. 13 could be combined to form the basic intermediate
structure shown in FIG. 15d.
[0225] FIG. 15e and 15f amplify FIGS. 15c and 15d respectively to
show that the CWCV stiffeners may be formed without viscoelastic
materials in the "feet" to promote good bonding and strength.
[0226] As stated above, the examples of FIG. 15 are basic building
blocks for damped panels, beams, surfaces, and structural members.
FIG. 15 shows only a few of the design combinations in the use of
CWC laminates, CWCV plates, viscoelastic damping materials, mixed
(if desired) with conventional composite or other materials. Any of
the CWCV plates and/or combinations of materials shown in FIG. 13
could be used to make the four basic stiffener building blocks, and
any of the exampled intermediate CWCV structures.
CWCV Plate Sandwiched Core Intermediate Structural Member
[0227] As shown in FIG. 16a (perspective view) a CWCV plate
sandwiched core intermediate structural member would consist of a
core (3), a structural laminate or a CWCV plate (1) shown with a
(for example) sinusoidal wave form, and a second structural
laminate or a CWCV plate (2) (no wave form shown), or, a special
surface treatment or material.
[0228] The sandwiched core (3) could consist of one or more of the
following: a) a honeycombed material (3a) b) and/or (3b) a
structural foam, special core material for sound proofing, wood, or
any other suitable core material(s) and combinations commonly used
to provide form to the structure.
[0229] The plate (1 & 2) could consist of one or more of the
following: a) one or more opposing CWC laminates constraining one
or more damping layers of viscoelastic or anisotropic viscoelastic
material, and/or b) a combination of CWC laminates, viscoelastic or
anisotropic viscoelastic damping layers, and conventional
composites or other suitable structural material, or any of the
CWCV plates represented in FIG. 13.
[0230] FIGS. 16b & 16c show cutaway end views of only a few of
the possible combinations of conventional, CWC laminates, and
viscoelastic materials (not shown to scale), and are meant to
elaborate on the structure shown in FIG. 16a.
[0231] The plate (2) of FIG. 16a is shown as item (7) in FIG. 16b,
could be composed of a conventional composite or other structural
material, and would thus represent the main load bearing member in
the laminate.
[0232] The plate (1) of FIG. 16a is shown as items (4), (5), &
(6) in FIG. 16b, and consists of one or more laminates and damping
layers (shown shaded). In one embodiment the laminates would
consist of opposing wavy patterned CWC laminates (5) & (6),
constraining viscoelastic or anisotropic viscoelastic damping
layers (4). An alternative embodiment would have some of the
laminates consist of CWC laminates, some would consist of
conventional laminates or other suitable materials, all having the
purpose of constraining one or more viscoelastic or anisotropic
viscoelastic damping layers (4). Two CWC laminates are shown in
FIG. 16b but it is possible to have any number of alternating
layers of opposing CWC laminates, viscoelastic damping layers,
conventional composites, anisotropic viscoelastic, or other
materials, according to the design criteria of the engineer. As
shown, the sandwiched core is joined directly to the load bearing
member (7) promoting strength and good bonding. Of course the order
of items 4-7 could be reversed where the load bearing laminate (7)
was located on the outside of the core surface.
[0233] The laminates (1 & 2) of FIG. 16a are shown as items
(4-8) in FIG. 16c, and consists of multiple CWC laminates and
damping layers (shown shaded). In one embodiment the laminates
would consist of multiple wavy pattern CWC laminates (5) & (6),
and would constrain multiple viscoelastic or anisotropic
viscoelastic damping layers (4). Some of the CWC laminates would be
of one pattern (5), with opposing CWC laminates (6). An alternative
embodiment would have some of the laminates consist of CWC
laminates, with some of conventional laminate or other material,
constraining the viscoelastic or anisotropic viscoelastic damping
layers (4). The plate sandwiched core could include conventional
composites or other materials (Items 7 & 8) to provide
additional strength. It is also possible to eliminate laminate (7)
on the surface of the sandwiched core in FIG. 16c which would bond
the viscoelastic material (4) directly to the sandwiched core.
[0234] As stated above, the examples of FIG. 16 are basic building
blocks for damped plates, panels beams, surfaces, and structural
members. FIG. 16 shows only a few of the design combinations in the
use of CWCV plates laminated to various core materials.
CWCV Stiffeners and Sandwiched Core Structures
[0235] FIG. 17 shows one of the many possible uses and combinations
of CWCV building blocks (plates and stiffeners) and sandwiched core
CWCV structures as discussed for FIGS. 13-16 above, in the design
of aerodynamic structures (1 & 2). FIGS. 17a and 17c show two
such possibilities using a typical airfoil (1 & 2) as an
example. In FIG. 17a multiple CWCV hat-stiffeners (FIG. 14) are
combined with one or more CWCV plates (FIG. 13) and joined together
to form the airfoil (1). In FIG. 17c two CWCV plates (FIG. 13) are
applied to a sandwiched core (FIG. 16) to form the airfoil (2) and
are reinforced by two C-channel CWCV stiffeners (or conventional
stiffeners).
[0236] FIG. 17b shows a blown up view of a portion of the
hat-stiffened CWCV airfoil of FIG. 17a. FIG. 17b makes use of a
CWCV hat-stiffened intermediate structural member illustrated in
FIG. 14b. Hollow spaces (10) in the airfoil (1) could be left open
for the passage of heated or cooling air, fuel, fluids, or coolant,
or could be filled with sound deadening materials, structural foams
or other materials depending on the requirements of the design. The
above discussion illustrates one example of the use of CWCV basic
building block concepts of FIGS. 13-16 used in aerodynamic
structures; others will be obvious to one skilled in the art. Such
CWCV aerodynamic structures could be used in wings, control
surfaces, propeller blades, turbine blades, rotor blades, fan
blades, and any other aerodynamic structure where damping,
strength, and stiffness are important.
[0237] FIG. 17d shows a blown up view of a portion of the CWCV
sandwiched core and C-channel stiffened airfoil of FIG. 17c. FIG.
17d makes use of both the C-channel stiffener building block
illustrated in FIG. 15c and the sandwiched core of FIG. 16b. Hollow
spaces (10) in the airfoil (2) could be left open for the passage
of heated or cooling air, fuel, fluids, or coolant, or could be
filled in with sound deadening materials, structural foams or other
materials depending on the requirements of the design. Such CWCV
aerodynamic structures could be used in wings, control surfaces,
propeller blades, turbine blades, rotor blades, fan blades, and any
other aerodynamic structure where damping, strength, and stiffness
are important.
[0238] As previously discussed, the basic building blocks shown in
FIGS. 13 through 16 (and discussed above) can be used in any number
of combinations to provide unique damping, strength, stiffness, and
acoustic properties. Only two possible designs have been shown;
others will be obvious to a person skilled in the art that such
combinations would be possible and desirable in certain design
situations. Thus it is not necessary to limit the designer to only
one family of the many designs shown in FIGS. 13 through 16. For
example, using high temperature matrix and damping materials in a
fan blade (as shown in FIGS. 17a & 4c) would allow the use of
CWCV materials in the construction of damped compressor and turbine
fans. Cooling air would be passed through the airfoil spaces (48)
as is done for conventional metallic fan blades and would control
the temperature of the materials. Thus any of the basic designs of
FIGS. 13 through 16 could be used in any combination to attain a
desired structural characteristic.
CWCV Stiffeners, Plates, and Sandwiched Cores Used in Panels,
Floors, Beams & Other Structures
[0239] The use of highly damped materials is beneficial in the
building of virtually every structure. In civil structures the use
of the CWCV building blocks of FIGS. 13-16 can provide both
structural and damping performance not previously attainable. The
same can be said for aerospace, automotive, and other structures
where damping and structural dynamics are important.
[0240] FIG. 18 shows a few of the many possible uses and
combinations of CWCV hat-stiffeners, I-beam stiffeners, and in the
construction of larger panels, floors, beams, and structural
members. FIGS. 18a through 18e show several such possibilities.
There are many ways of making panels or floors from the various
CWCV building blocks (e.g. CWCV plates and stiffeners). FIG. 18a
shows a typical aircraft floor composed of CWCV I-beams from FIG.
15a coupled to a conventional floor plate or a CWCV plate from FIG.
13. FIG. 18b adds an additional conventional or CWCV plate for
added stiffness. FIG. 18c makes use of CWCV plates from FIG. 13 and
various combinations of CWCV hat-stiffeners from FIG. 14. Any
combination of the CWCV plates (FIG. 13) or stiffener building
blocks (FIGS. 14-16) can be used to construct these highly damped
panels. The examples in FIG. 18 are shown with a flat shape, but
these same combinations can be formed in any number of geometric
shapes.
[0241] There are many more possible combinations of CWCV laminates,
stiffeners, core materials, etc. that will be obvious to one
skilled in the art.
CWCV Building Blocks Used in Skis and Other Sports Equipment
[0242] Skis, snowboards, waterskis and other sports equipment can
benefit from the addition of structural materials with inherent
damping as represented by the use of CWCV building blocks. For
example, downhill racers rely on the dynamics of their skis ability
to provide solid contact with the ground and maintain control. Skis
that chatter are a hazard. Skis with inherent structural damping
are therefore of great value to the sport.
[0243] FIG. 19 shows an example of one of the many possible uses of
CWCV structures in the design of skis, snowboards, etc.
[0244] As shown in FIG. 19a (perspective view) a CWCV enhanced ski
would consist of a CWCV covered core (1 & 4) shown with a (for
example) sinusoidal wave form. The core (4) could consist of any of
the materials discussed in FIG. 16 above such as honeycomb, foam,
wood, etc. The core is strengthened by the addition of a CWCV plate
(1) which can consist of any of the examples discussed in FIG. 13,
and strengthened by the addition of any of the basic CWCV
stiffeners or other intermediate structures as discussed in FIGS.
14-16. Metallic (or other suitable material) edges (2) would be
bonded to the CWCV wrapped core (1 & 4). Typically a special
plastic or other material is bonded to the bottom of the ski (3) to
provide protection to the ski and to give the ski special surface
properties for better performance. Likewise a protective coating is
applied to the top and sides of the ski (5) to provide protection
to the core structure.
[0245] FIGS. 19b through 19d show cutaway end views of examples of
the use of CWCV plates and other materials in the design and
construction of a ski. In general, the combinations of conventional
and CWCV plates (FIG. 13), shown in FIGS. 19b-19d mirror the
possible combinations discussed in conjunction with FIG. 13. The
various combinations of CWC laminates (7 & 8) combined with
viscoelastic material (6), conventional laminates or isotropic
materials (9) and special protective surface materials (3) can be
arrayed as shown depending upon the dynamic properties desired.
[0246] Two specific examples of skis that have been built using
CWCV plates and conventional materials are shown in FIGS. 20 and
21. The ski discussed in FIG. 19 is shown in FIG. 20 assembled
(FIG. 20a) and in exploded view in FIG. 20b. In FIG. 20
conventional laminates "packs" (6) were replaced by combinations of
unidirectional carbon composite (7) viscoelastic layers (8) and
opposing CWC laminates (9 & 10). Torsional rigidity was
provided by the .+-.45.degree. bi-directional composite cloth. The
combination is laminated on to the core (4) and enveloped by
protective coatings (3 & 5) and cured in the standard
manner.
[0247] An alternative embodiment of the ski shown in FIG. 20 is
represented in FIG. 21 shown assembled (FIG. 21a) and in exploded
view in FIG. 21b. As shown in FIG. 21 the basic structure discussed
for FIG. 20 applies in this figure as well, except that the
alternating layers of viscoelastic (8) and CWC laminates (9 &
10) are wrapped around the bi-directional cloth-covered core (4).
The scaling shown in FIGS. 19-21 are exemplary of a few of the many
assembly methods available to the designer. By varying the amounts
of conventional composites (7 & 11) and CWCV plates (8-10) it
is possible to "tune" the dynamics of the ski.
[0248] There are many other combinations of viscoelastic or
anisotropic viscoelastic materials, and conventional composites,
special coatings, or other materials which can be used to design
and build the ski, and will be obvious to one skilled in the
art.
[0249] For example, in the case of the water ski, it may be
desirable to eliminate the metallic edges (2) and the special
covering for the bottom (3) or the top & sides (5). In this
case, the CWC laminates on the surface would provide the aesthetic
covering as well as the damping and structural properties of the
ski.
[0250] The example CWCV ski structures discussed above could be
used for snow skis, snow boards, surf boards, slalom skis, beams,
boards, and many sports equipment or structural components where
damping, strength, and stiffness are important. CWCV Tubes.
[0251] A CWCV tube can be made from the basic CWCV plate building
block discussed in FIG. 13. Although the basic structure shown in
FIG. 22e was contemplated by Dolgin, the use of stepped CWCV plates
as shown in FIGS. 22f and 22g was not. Neither was the use of the
non-sinusoidal wave forms of FIGS. 1-5. The use of the concepts in
FIGS. 1-5 and 13 in the design and the manufacture of tubular
structures can provide damping and reinforcement to diverse
structural components such as concrete pillars, pilings, beams, and
foam or other cored structures. For example, the use of CWC
bi-directional cloth where the fill fibers are straight and the
wavy fibers are oriented as in FIG. 22a will provide containment,
damping, and structural reinforcement for a concrete beam or
column. The use of CWCV structural reinforcement and damping will
provide additional safety margin, survivability, and increased
service life to a concrete structure. It is well-known that the use
of composite materials as a surface treatment for standard concrete
structures is highly desirable and becoming more common. None of
the current methods, however, add inherent damping to the
structure.
[0252] The CWCV tubes shown in FIGS. 22b through 22g can be used in
the manufacture and improved dynamics of sports equipment as
diverse as golf club shafts, arrow shafts, tennis rackets and
similar devices, baseball bats and similar devices, poles, shafts
(such as helicopter and automotive drive shafts), antennae
components, bicycle components and frames and fishing rods.
[0253] The tubular examples of FIG. 22 are shown with a round cross
section but any cross section can be used including elliptical,
square, rectangular, polygonal, aerodynamic, or even a special
irregular shape or combination of shapes designed to optimize
structural parameters. The tubular examples of FIG. 22 are also
shown of constant and uniform cross section throughout the length
of the tube. Of course it is possible to taper the tube, bend the
tube in any reasonable shape, or even create an irregular taper and
shape along its length depending on the application. It is a common
practice to construct a tube on a straight mandrel (for example)
remove it prior to curing, place it in a curved mold, and form
curved tubes of constant or variable cross section and shape. Such
a process would be used in the manufacture of a CWCV damped tennis
racket (for example). Of course any of the material combinations
discussed in conjunction with FIGS. 1-5, 13-16, could be used in
the manufacture of a CWCV tube.
[0254] A single layer of wavy composite has a fiber lay that
oscillates between a negative maximum angle and a positive maximum
angle in a pre-determined pattern. As a result, the individual
laminae will vary in stiffness and displacement characteristics
along its length as the angle of the fiber changes. Thus where the
angle is 0.degree. relative to the length of the waveform, the
laminae will have the characteristics of a 0.degree. unidirectional
composite, and where the angle diverges from 0.degree. the laminae
will have the characteristics of an off-axis unidirectional
laminae. If several opposing wavy composite laminae are joined
together in a symmetric lay-up (see FIG. 23), the laminate will
exhibit quasi-isotropic properties at any point along the
length.
[0255] Refer to FIG. 25. Items 5 and 6 refer to opposing pairs of
wavy composite laminae. Where the angle is at a .+-. maximum (item
10), the properties of the laminate will be like a .+-.
unidirectional crossply. These areas where the angles are at a .+-.
maximum will resist in-plane shear loads effectively but will have
a lower longitudinal or lengthwise stiffness. Where the angle is at
0.degree. (item 11) the laminate will have the properties of a
0.degree. unidirectional lay-up (Pratt 1999). These areas (where
the angle of the fibers is 0.degree. relative to the longitudinal
direction) will not resist shear loads effectively but will have a
greater lengthwise stiffness. These localized differences in
stiffness can be overcome by combining two pairs of wavy composite
laminae into a single laminate as is shown for item 7. The
structure of the wavy laminate enclosed by item 7 is hereafter
termed "wavy crossply laminate."
[0256] Thus, for one pair of opposing wavy laminae, the angle will
be at a .+-. maximum but the second pair of opposing wavy laminae
will have a fiber angle that is at 0.degree. or nearly 0.degree.
relative to the general direction of the laminate. This gives the
laminate an equivalent unidirectional lay-up of four total layers
where two of the layers are unidirectional plies with a .+-. fiber
orientation, and the other two layers were equivalent to two
0.degree. unidirectional laminae. The difference is that the
construction of a unidirectional version of a crossply laminate
cannot be easily automated; the construction of a wavy crossply
laminate can be automated. In the process of characterizing the
properties of damped wavy composites, several sample tubes
constructed from wavy composite with constrained viscoelastic
layers were compared to equivalent undamped unidirectional crossply
tubes. It was found that damped wavy tubes took significantly less
time to fabricate. As a result, and in an effort to save labor
time, several undamped tubes were manufactured using the lay-up
shown in FIG. 25, item 5 (one pair) as a replacement for the
undamped unidirectional tubes because of the ease with which wavy
tubes could be fabricated. The realization of the superior
handling, excellent stiffness and strength, and significant time
savings led to additional discoveries which are the subject of the
present invention.
[0257] The following discussion further amplifies the advantages of
using wavy composite pre-preg in wavy crossply lay-ups. FIG. 26
illustrates three typical crossply lay-ups that use several
unidirectional pre-preg plies (item 2) to build a laminate with
quasi-isotropic properties. In reference 10, Rienfelder, et al
showed how to construct a rotary wing spar using different
materials and ply stacking methods and cited superiority of
consolidation of the laminate, uniformity, and tailorability of the
laminate combinations as advantages. They further cite the
disadvantages of fiber winding techniques for this application as
"relate[d] to difficulties associated with expanding/urging the
fibers against the mold surfaces of the matched metal mold." It can
be concluded that in some applications, fiber plies or laminae made
from unidirectional materials cut off-axis will be preferable to
the use of fiber winding methods and that continuity of fibers of
such plies will be interrupted. The authors state that such plies
were butt-joined together and that such joints from additional
plies above and below in the stacking sequence were offset so that
adjacent butt-joints would not coincide.
[0258] This concept is shown in general in FIGS. 5 and 6. Pre-preg
made with unidirectional fibers comes in finite widths, typically
up to 1.5 meters in width, in very long lengths. The same is true
with cloth pre-preg, and wavy composites. Because of the limited
widths of pre-preg, there is a finite length of off-axis material
that can be cut from a roll of unidirectional pre-preg. In FIG. 27,
several unidirectional plies (12) are cut from a long continuous
sheet of unidirectional material. The plies are then buttjoined
(13) and overlapped (14) with other plies from the same cut of
material. The weakest link in the laminate is the seam between
butt-joined plies (13) where fiber continuity is interrupted. Thus
to obtain a viably strong laminate with an off axis orientation, a
minimum of two laminae are required.
[0259] Wavy composites do not have this limitation. As shown in
FIG. 27, two or more plies (1) of wavy pre-preg can be placed
adjacent to each other to create a wider laminae (15). When using
concepts shown in FIG. 25, the wider wavy laminae can be combined
in different ways to form a laminate with the desired properties.
To further amplify the advantages of wavy composite, refer to FIGS.
3 thru 6.
[0260] In order to make a crossply laminate from unidirectional
pre-preg similar to concepts shown in FIG. 26 with a ply stacking
sequence of 0.degree./+45.degree./-45.degree., it would be
necessary to cut the off-axis plies as shown in FIG. 27 item 12.
Several such plies would be butt-joined and overlapped as shown in
FIG. 28 items 13 and 14. While the 0.degree. ply (item 16) is
continuous in this drawing, there are significant interruptions of
fiber continuity in the off-axis plies. All of this is typically
done by hand and is very labor intensive.
[0261] If, however, the designer were to use wavy composite, the
equivalent of the 0.degree./+45.degree./-45.degree. laminate could
be completed using wavy plies offset as shown in FIG. 25 item 7. If
hand labor is used, the steps required to accomplish the desired
laminate are greatly reduced. Instead of having to cut separate
laminates as shown in FIG. 27, item 12, the fabricator uses
successive wavy layers of any desired length to form the wavy
crossply laminate. In fact, it is very possible for this process to
be automated by feeding (for example) four spools of wavy composite
through a pair of pinch rollers with the patterns offset
appropriately, to create a continuous roll of wavy crossply as
shown in FIG. 25, item 7. The beginnings of such a process are
shown in FIG. 28 (bottom) where the second wavy composite layer (1)
is overlaid on the first layer (15). FIG. 28 shows the next layer
of wavy composite (1) offset to the right of the base layer (15)
for clarity. In actual practice both layers (1 and 15) could begin
at the end; this figure is only illustrative of the concept. Of
course there are many methods and mechanism whereby wavy layers can
be combined to form wavy crossply laminates including successive
passes by a single axis laminator, multiple feed rolls, etc., and
even manual labor methods. All will be significantly easier and
more economical than current methods of producing unidirectional
pre-preg based crossply laminates.
[0262] The present invention includes a structure such as is shown
in FIG. 23 where several layers of wavy composite (1 and 3) are
used to build a "balanced" wavy composite laminate.
[0263] The present invention also includes a laminate consisting of
a mix of wavy composite layer(s) (items 1 and/or 3) and
unidirectional layers (2) as shown in FIG. 24. In this figure the
laminate consist of two opposing wavy layers (1 and 3) and one
transverse unidirectional ply (2). This is a very lightweight,
efficient lay-up that has been used to produce undamped tubes with
excellent stiffness and improved strength properties. It has been
found, that the lamination of at least one transverse ply (2) and
at least one wavy ply (1 or 3) provides greater strength. When a
single layer of wavy composite is pulled to failure (along the
strong or longitudinal axis), the failure generally occurs in the
matrix where the angle of the fiber is at a .+-. maximum. The
matrix splits between the fibers. If fibers are added generally
perpendicular to the wavy fiber lay, then the laminate failure
occurs at a much high stress level because the transverse fibers
resist the transverse stresses efficiently. It is also possible to
orient two or more wavy layers transversely to each other as is
shown in FIG. 25 item 4. Such a laminate structure would be useful
in providing quasi-isotropic properties to sculpted surfaces where
special properties or laminating issues are important.
[0264] The most useful configuration is shown as items 5-9 in FIG.
25. Items 5, 6, and 8 represent pairs of opposing wavy composite
laminae joined together. The two (or more) wavy laminates need not
"oppose " each other (e.g. have a one-half waveform phase lag or
offset) to conform to the meaning of the present invention. It may
be useful to cause a more or less than half waveform phase lag as
demonstrated in the area enclosed by item 7 of FIG. 25.
[0265] Combining two or more "pairs" of wavy laminae need not be
joined together along their longitudinal axes but may be laid at
some off-axis angle with respect to each other as is shown in FIG.
25, items 5 and 8. This will give a unique crossply effect as shown
in the area enclosed by item 9. Although the pairs of wavy
laminates (FIG. 25, items 5 and 8) are shown essentially
perpendicular to each other, it is also possible to vary this angle
more or less to accomplish unique laminate properties. For example,
it may be desirable to place the pairs of wavy laminates at a
.+-.30.degree. angle or some other angle with respect to a
reference line as is commonly done with unidirectional plies. These
different angular orientations are contemplated by this
invention.
[0266] To further illustrate the capability of wavy crossply
laminates, the following table documents the equivalent axial
stiffness of several different configurations of wavy crossply
laminates using (for example) a typical carbon fiber-resin
combination to represent the material properties of both
unidirectional and wavy composite. Table 1 shows the configuration
of each laminate. Each laminate is defined by the words
"unidirectional", or "wavy crossply", or "wavy crossply &
unidirectional" defining the materials used in the lay-up. This is
shown in the "Laminate" column of the table. The laminate
configuration is further defined by the angle of the plies relative
to the longitudinal direction of the sample tube used to model the
lay-up. This is shown in the "Configuration" column of the table.
For example, "0.degree." means all fibers are oriented at zero
degrees to the reference, or run longitudinally in the tube. The
relative axial stiffness of the laminate is given in the column
labeled "Axial modulus." This represents the smeared axial material
properties of the lay-up. Axial modulus represents the relative
ability of the laminate to resist tension or compression loads, and
even bending loads if the neutral axis shear forces are ignored.
The "Shear modulus" column represents the ability of the laminate
to resist torsion or shear loads.
1TABLE 1 Laminate Configuration Axial modulus Shear modulus 1.
Unidirectional 0.degree. 142.2 GPa 5.2 GPa 2. Unidirectional
+30.degree./-30.degree. 51.4 GPa 29.2 GPa 3. Unidirectional
0.degree./+30.degree./-30.degree. 84.3 GPa 21.5 GPa 4. Wavy
crossply .+-.30.degree. wavy (one pair) (FIG. 25, item 5 or 82.4
GPa 12.6 GPa 6) 5. Wavy crossply .+-.45.degree. wavy (two pair)
with quarter 53.9 GPa 27.5 GPa waveform offset between pairs (FIG.
25, item 7) 6. Wavy crossply .+-.30.degree. wavy (one pair) with a
90.degree. 72.6 GPa 10.9 GPa & Unidirectional unidirectional
transverse ply (FIG. 24) 7. Wavy crossply .+-.30.degree. wavy (two
pair) with quarter 88.6 GPa 20.0 GPa waveform offset between pairs
(FIG. 25, item 7) 8. Wavy crossply .+-.30.degree. wavy (two pair)
with quarter 73.7 GPa 16.0 GPa & Unidirectional waveform offset
between pairs, with a 90.degree. unidirectional transverse ply
(FIG. 24 and FIG. 25 item 7 combined) 9. Wavy crossply
.+-.30.degree. wavy (two pair) with quarter 98.0 GPa 17.8 GPa &
Unidirectional waveform offset between pairs, with one 0.degree.
unidirectional ply.
[0267] Laminate 1 is a unidirectional fiber composite lay-up that
shows the 0 degree properties of the fiber reinforce composite used
to model all subsequent lay-ups. Laminate 2 shows the properties of
a conventional .+-.30 degree unidirectional composite crossply
lay-up. Note that the equivalent axial modulus of laminate two is
considerably reduced from that of laminate 1, but the equivalent
shear modulus is greatly improved over the shear modulus of
laminate 1. This is a classic example of how crossply composites
lose axial modulus rapidly as the angle of the fiber diverges from
zero degrees, but their ability to resist shear loads improves.
[0268] As discussed above and shown in FIG. 28, a unidirectional
crossply laminate is difficult to fabricate with automated means.
However, as shown in Table 1 (laminate #2), crossply laminates are
useful in providing resistance to both axial and shear loads. If
more axial stiffness is required, a unidirectional 0 degree ply can
be added. The results of this combination are shown as laminate #3
in Table 1. The axial modulus is improved by 64% relative to
laminate #2 but the shear modulus is reduced 26%.
[0269] Wavy composite can be used to create wavy crossply laminates
equivalent to the unidirectional crossply laminates discussed
above. Wavy crossply laminate #5 is equivalent in both axial and
shear modulus to unidirectional crossply laminate #2. Likewise,
wavy crossply laminate #7 is equivalent in both axial and shear
modulus to unidirectional crossply laminate #3. Both wavy crossply
laminates are significantly easier to fabricate, do not cut fibers
(and therefore do not show any seam), and can be readily automated.
The same cannot be said for the two unidirectional crossply
laminates.
[0270] The remaining entries of Table 1 example only a few of the
many different combinations possible by using wavy composite
materials. For example, wavy crossply laminate #4 represents the
axial and shear modulus of one pair of opposing wavy laminae (FIG.
25, item 5 or 6). This combination has a 60% greater axial modulus
than the .+-.30 degree unidirectional crossply lay-up (laminate #2)
but a 57% lower shear modulus. It is exampled here because it
represents the simplest wavy crossply laminate. Obviously, it is
possible to modify the characteristics of the laminate by changing
the waveform, offset, or by orienting the wavy laminae off-axis.
This example represents only one combination of parameters and
their effects on the stiffness of the laminate thus created.
[0271] If greater transverse strength was desired in the crossply
laminate, the designer would add an additional layer of
unidirectional composite. This is shown in laminates #6 which is a
modified version of #4, and in laminate #8 which is a modified
version of laminate #7. Both can still be readily automated in
fabrication since the 90 degree layers could be added easily.
Additionally, 0 degree unidirectional layers can be added to
augment the axial modulus without unduly sacrificing the shear
modulus. This is shown as laminate #9 in Table 1 and compares
favorably with laminates 3, 7, and 8.
[0272] The present invention does not limit the waveforms used to
identical wave patterns, periods, to a particular waveform (such as
a sine wave, cosine wave, etc.), a particular orientation, or to a
particular offset. The properties desired in the laminate may
require a non-periodic waveform or a combination of waveforms of
any type, and unidirectional or woven cloth laminae. The selection
of waveforms, materials, orientations, or offsets to use will
depend on the properties desired in the laminate. The selection
will be obvious to one skilled in the art. The wavy laminates
discussed here and illustrated in the figures are for example
purposes only.
[0273] Finally, the range of possible uses of the example wavy
crossply lay-ups shown in Table 1, is potentially limitless. In
reference 12, a construction for a rotary wing spar is revealed
which uses unidirectional and woven fiber composite layers to
provide efficient axial, bending, and torsional stiffness. Although
the examples of Table 1 were based upon the analysis of a sample
tube, the same or similar wavy composite lay-ups could be used to
construct an equivalent spar at a greatly reduced costs. Other
applications include automotive, aerospace, and marine drive
shafts, composite wing structures of all types, panels, composite
I-beams, channels, and virtually an endless combination of
possibilities. Composite arrow shafts and golf club shafts would
likewise benefit from greatly reduced labor costs in construction.
Other applications will be obvious to those skilled in the art.
[0274] By combining the concepts shown in references 1, 15, 5, and
6, it is possible to create a lightweight, damped, golf club shaft
that improves "feel", dramatically reduces free vibrations, widens
the "sweet" spot on the club head, and reduces shock to the user's
anatomy.
[0275] Refer to FIG. 25. In the preferred embodiment, major
stiffness in axial, bending, and torsion in the golf club shaft (or
other tubular structures) is provided by two pairs (or more) of
opposing and offset wavy composite laminae as shown in FIG. 25,
item 7. Items 5 and 6 refer to opposing pairs of wavy composite
laminae. Where the angle is at a .+-. maximum (item 10), the
properties of the laminate will have the properties of a .+-.
unidirectional crossply. These areas where the angles are at a .+-.
maximum will resist in-plane shear loads effectively but will have
a lower longitudinal or lengthwise stiffness. Where the angle is at
0.degree. (item 11) the laminate will have the properties of a
0.degree. unidirectional lay-up (Pratt, reference 15). These areas
(where the angle of the fibers is 0.degree. relative to the
longitudinal direction) will not resist shear loads effectively but
will have a greater lengthwise stiffness. These localized
differences in stiffness can be overcome by combining two pairs of
wavy composite laminae into a single laminate as is shown for item
7, termed "wavy crossply laminate."
[0276] Thus, for one pair of opposing wavy laminae, the angle will
be at a .+-. maximum but the second pair of opposing wavy laminae
will have a fiber angle that is at 0.degree. or nearly 0.degree.
relative to the general direction of the laminate. This gives the
laminate an equivalent unidirectional lay-up of four total layers
where two of the layers are unidirectional plies with a .+-. fiber
orientation, and the other two layers were equivalent to two
0.degree. unidirectional laminae.
[0277] If this wavy crossply structure is combined with one or more
viscoelastic layers and one or more constraining wavy composite
layer, the result is a lightweight golf club shaft with high
damping and excellent bending and torsional stiffness.
Additionally, the wavy fiber composite has an aesthetically
pleasing look which in good daylight seems to shimmer and sparkle.
Golf club shafts can be constructed entirely from wavy composite
and viscoelastic damping materials. The primary bending and
torsional load resistance is provided by a wavy crossply structure;
damping is provided by two viscoelastic layers and two double ply
wavy composite constraining layers, as shown in part in FIG. 1. The
overall construction of the golf club shaft is shown in FIG.
32.
[0278] As seen in FIG. 32b, the wavy fiber lay runs the length of
the golf shaft that is preferably tapered. The generalized laminate
structure is shown in cross section in FIG. 32a where Item 1
represents one layer of wavy composite of one pattern, Item 3 is an
opposing wavy layer, Item 2 is the viscoelastic damping layer(s),
and Item 4 is the main load bearing part of the shaft. Item 4 is
preferably made from four or more wavy layers arranged in a wavy
crossply scheme (FIG. 25, Item 7). It is also possible to construct
the load bearing portion of the shaft (Item 4) from conventional
unidirectional laminates or isotropic materials. At the handle end
(Item 5), the two layers, Items 1 and 3 are bonded together by
removal of the viscoelastic layers (Items 2) to provide additional
load coupling to the load bearing layer (Item 4). At the tip end
(Item 7), the viscoelastic damping layers (Item 2) are removed to
provide both good load coupling to the load bearing layer (Item 4),
and to provide an area where the length of the club can be tailored
to the desires of the owner. These methods of removing the
viscoelastic from between the wavy layers or wavy layer and load
bearing structure are generally termed "welds". Additionally, in
these "weld" areas, the viscoelastic can be replaced with wavy,
unidirectional, or cloth composite to provide additional strength
and load resistance.
[0279] Other methods of construction of the damped wavy golf club
shaft are possible including but not limited to progressively
welding the various viscoelastic layers, rearranging the order of
layers, or adding or subtracting additional layers of viscoelastic,
wavy constraining layers, or load bearing layers, as shown in FIG.
22 and discussed in Reference 1. The characteristics of the
structure can be modified by interposing unidirectional or
multidirectional materials in the load bearing layers as shown in
FIG. 24, and discussed in Reference 15. Damping and stiffness
characteristics can be modified by the addition of unidirectional
or bi-directional materials in the structure of the constraining
layers as shown in FIGS. 4 and 5. The minimum structure for a golf
club shaft dampened with a wavy composite layer is a shaft, such as
a steel or composite shaft, with at least one viscoelastic layer
affixed to the surface of the shaft (on the inside or outside)
wherein the viscoelastic layer is constrained by at least one
sinuous wavy composite layer attached to the viscoelastic layer on
the side of the viscoelastic layer that is opposite to the side of
the viscoelastic layer adjacent to the shaft.
[0280] The structure shown in FIG. 30 is useful in that the
transverse fibers strengthen the wavy composite against premature
failure. Failure occurs in the wavy layers generally when the loads
applied to the structure exceed the rupture strength of the matrix
where the angle of the wave is at a .+-. maximum. By adding
additional layer(s) of transverse fibers this type of failure can
be avoided while preserving the damping characteristics of the wavy
composite structure.
[0281] If greater damping, stiffness, or strength is desired, it is
possible to place intermediate "welds" by removing viscoelastic
material from key areas of the laminate as shown in FIG. 31, Item
5. Removing viscoelastic material from these areas shortens the
effective length of the damping area and allows better coupling of
the dynamic loads along the length of the structure.
[0282] The structure of the golf club shaft shown in FIG. 32
resulted in a capable and lightweight shaft that provides less club
head "flutter", a wider "sweet spot", greatly reduced vibration,
and reduced shock transmission to the user. The wider "sweet spot"
is due to the reduction of lateral and torsional vibration
magnitudes of the head during contact with the ball. Typically the
"sweet spot" on a club head is the approximate size of a quarter.
Contact in this area of the club head with the ball, results in a
greater transference of energy to the ball on a conventional golf
club. Striking the ball outside of the "sweet spot" results in
significant loss of energy transference on a conventional club, and
greater shock to the user. The prototype club made from a shaft as
shown in FIG. 32 had no discernable limits to the "sweet spot".
Thus, the construction of a golf club with this improved shaft
results in greater consistency, energy transference, with a
resultant increase in range, and accuracy. The reduction in shock
transference to the user is another benefit of this shaft
structure. In conventional shafts, this ringing of the golf club
after impact induces sympathetic ringing in the hands and arms of
the user and can cause damage in the long term, similar to "tennis
elbow" and other repetitive type injuries. A golfer who anticipates
the "sting" of the swing will be reluctant to hit the ball normally
and will have a tendency to "pull" the swing, with subsequent
reduction in range, and loss of accuracy and consistency.
[0283] The structure of the golf club shaft can easily be extended
to the production of baseball bats and similar devices where, for
example, the overwrapping of the handle and part of or all of the
barrel would provide both additional strength and resistance to
splitting (for wooden bats). Additionally, the dramatic reduction
in resonance amplitudes and duration after impact will reduce or
eliminate the "sting" often associated with off-sweet spot hits.
For metal bats or bats made from composite, this wavy composite
damping concept can be added to the interior of the bat during
construction or exterior during retrofitting. In this case,
experience has shown that the reduction of vibrations and sting is
likewise very apparent.
[0284] The preferred configuration for a wooden bat is to wrap the
handle from about one inch from the butt end to a point
approximately 18 inches from the butt end. The first four layers of
wavy composite would be two pairs of opposing wavy composite with
one pair offset from the other pair by a quarter wavelength as
shown in FIG. 25 item 7. If damping was not desired and only
reinforcement of the bat handle was desired, the four layers of
wavy composite would provide the necessary reinforcement to prevent
the handle from breaking. If damping is desired, wavy damping
layers would then be added using opposing pairs of wavy composite
combined with viscoelastic as shown in FIG. 32 and discussed for
the golf club. Only one damping layer would be required but damping
would be half of that of a pair of opposing wavy damping
layers.
[0285] The preferred configuration for a hollow metal bat would be
to affix the wavy composite damping and reinforcement layers to the
inside of the bat by wrapping an expanding mandrel with wavy
composite layers and viscoelastic in as many single or opposing
pairs as desired, insert the mandrel into the barrel end of the
bat, expand the mandrel, and cure the wavy composite-viscoelastic
damping layers inside the metal bat. This preferably would happen
in the first 18 inches of the handle (from the butt end) since this
is the area where most of the vibrations that "sting" a batter
occur. If reinforcement is desired, crossply wavy layers could be
added to the damping layers and the mandrel inserted as previously
discussed. In this manner, the reinforcing layers of wavy crossply
material would be next to the metal on the inside of the bat, and
the damping layers towards the interior of the hollow bat. For
retrofits to existing metal bats, the handles could be wrapped as
was discussed for the wooden bats.
[0286] The structure of the golf club shaft can easily be extended
to the production of fishing rods by simple scaling. The benefits
would be the reduction of tip resonance and magnitude of vibration
which causes the lure to have an unnatural movement.
[0287] This structure can be applied to the production of highly
damped gun barrels where Item 4 of FIG. 32 would include a metallic
liner for the rifling and wear resistance to the travel of the
projectile through the tube. The obvious benefit is the reduction
of "barrel slap" where the barrel vibrates as the projectile
travels the length of the tube. This is a major source of
projectile dispersion in large gun tubes. These benefits will also
be evident in the use of these damping concepts on rifles. Likewise
the use of these methods in the production of arrow shafts would
result in greater accuracy and consistency.
[0288] While the structure of the golf shaft shown in FIG. 32 is
tapered, there are many more applications where the cross section
may be held constant or varied by some other criteria. The
production of drive shafts of all kinds can benefit from this
method of construction. By using the methods and concepts discussed
above and shown in FIGS. 1-7, it is possible to construct drive
shafts for helicopters, automobiles, marine applications, and other
high speed turning operations where resistance to torsional,
bending, and the "super critical" modes are needed. The reduction
of torsional vibration magnitudes reduces both the magnitude of
stresses and strains experienced by the shaft, and reduces impact
loading on gear boxes that may be attached. Prevention of the
"super critical" mode of vibration where the bending frequency of
the shaft matches the rotational speed of the shaft is the most
pressing need in (for example) helicopter drive shafts. Both
damping and stiffness are critical to prevention of catastrophic
failure of the shaft in this mode. Avoidance of these failure modes
is provided by the unique characteristics of the construction
methods and concepts discussed above. Only the numbers of damping
and constraining layers, and which material combinations are used
will vary depending on the individual application and the expected
loads.
[0289] These methods can be used to construct highly damped and
capable boring bars for machining of deep cavities on lathes. Other
machine tool components that would benefit from these methods
include spindle extensions where resistance to both bending and
torsional loading and reduction of resonance magnitudes is
important to the prevention of chatter.
[0290] Likewise the use of these methods can easily be adapted to
the production of oil drilling pipe where the damping and stiffness
offered by the design shown in FIG. 32 would prevent the "pogo
effect", and torsional chattering of the cutting head. In this
application, both axial, bending, and torsional chatter can be
prevented by this construction method, and drill pipe breakage or
damage to the cutting head, in the hole can be avoided.
[0291] The production of larger versions of the concept shown in
FIGS. 1-7 can be used to provide containment to reinforce concrete
pillars, columns, and beams use in the construction of bridges,
buildings, peers, pilings, and other civil structures. In addition
to providing containment to the concrete, the damped wavy structure
provides protection from the elements (especially salt and water
corrosion of rebar), and most importantly, provides additional
strength, stiffness and inherent damping to the structure. This
would result in structures that would last for 75 years or more,
provide survivability of the structure during earthquakes, and
provide increased occupant comfort from natural sway and vibration
in tall structures.
[0292] The concepts illustrated in the figures and discussed above
need not rely solely on the use of waveforms that are oriented with
the major axis of the tube or structure. Additionally, it is
possible, with allowance for the differences in diameter of the
laminate and a corresponding requirement to change the wavelength
of the pattern, to place one or more of the waves off-axis to the
length of the mandrel, or tube. In this case careful planning and
alignment of the waveforms is required to provide for matching of
the opposing waveforms necessary for efficient damping performance.
The waveform required for any particular layer will be a function
of the effective diameter of the laminate in the structure, the
previous waveform, and the off-axis angle of the laminate. This
insures that the opposing waveforms in successive layers oppose
each other properly throughout the thickness of the structure where
the diameter and thus effective length of the off-axis orientation
increases in proportion to the diameter of the laminate. The major
advantage of an off-axis orientation of the wavy damping layers
would be the increased efficiency, stiffness, and damping
properties of the laminate for torsional loads.
[0293] The concepts illustrated in the figures and discussed above
need not rely solely on the use of waveforms that are sinusoidal
but may make use of any sinuous waveform that taylors the damping
and stiffness of structure. As long as the minimum diameter of the
curvature of the wavy composite is not excessive which would have a
tendency to promote fiber breakage, the waveform may appear to have
any useful sinuous shape. Additionally, all these designs
contemplate the use of bi-directional composite cloth that has had
the warp sinuously shaped, with the fill fibers of the same fiber
type or of a different type in various percentages of fill. The
advantage of fill fibers in the wavy composite pre-preg is that it
prevents premature failure of the laminate at the areas of maximum
fiber angle.
[0294] Other applications will be obvious to those skilled in the
art.
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