U.S. patent application number 09/899390 was filed with the patent office on 2002-06-13 for contoured composite structural mambers and methods for making the same.
This patent application is currently assigned to DALE FRANCIS OBESHAW. Invention is credited to Obeshaw, Dale Fracis.
Application Number | 20020071920 09/899390 |
Document ID | / |
Family ID | 22807863 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020071920 |
Kind Code |
A1 |
Obeshaw, Dale Fracis |
June 13, 2002 |
Contoured composite structural mambers and methods for making the
same
Abstract
Contoured composite structural members and methods for making
the same are described. The contoured structural members comprise
composite materials and the contoured structure can be provided by
tube rolling (or roll wrapping) the composite materials together
and then, if necessary, bonding them or connecting them. The outer
surface of the structural member can be provided with a polygonal
shape during the process of manufacturing. With a contoured
structure and an outer polygonal shape, applications for the
structural members of the present invention are increased.
Inventors: |
Obeshaw, Dale Fracis; (Salt
Lake City, UT) |
Correspondence
Address: |
EDMUND P. ANDERSON
DELPHI TECHNOLOGIES, INC.
Legal Staff, Mail Code: 480-414-420
P.O. Box 5052
Troy
MI
48007-5052
US
|
Assignee: |
DALE FRANCIS OBESHAW
|
Family ID: |
22807863 |
Appl. No.: |
09/899390 |
Filed: |
July 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60216636 |
Jul 7, 2000 |
|
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|
Current U.S.
Class: |
428/34.1 |
Current CPC
Class: |
B62D 29/001 20130101;
B62D 21/09 20130101; B62D 21/15 20130101; Y10T 428/1241 20150115;
Y10T 428/12493 20150115; B21C 37/154 20130101; B32B 3/28 20130101;
F16L 9/003 20130101; Y10T 428/139 20150115; F16L 9/02 20130101;
B32B 3/30 20130101; A63B 60/54 20151001; Y10T 29/53652 20150115;
B32B 1/08 20130101; B21C 37/15 20130101; B29D 24/002 20130101; B62D
29/005 20130101; Y10T 428/1234 20150115; B62D 21/00 20130101; Y10T
428/12361 20150115; Y10T 428/13 20150115; B29D 99/0035 20130101;
B29D 24/004 20130101; B29L 2031/324 20130101; F16L 9/19 20130101;
F16L 9/18 20130101; B65H 75/10 20130101; B32B 15/08 20130101; B32B
3/12 20130101; Y10T 428/24165 20150115; B29C 70/32 20130101; B65H
2701/5114 20130101; B32B 15/04 20130101; F16L 9/006 20130101; F16L
7/00 20130101; Y10T 428/12375 20150115; Y10T 428/24149 20150115;
B32B 15/01 20130101; B32B 27/04 20130101; B62D 29/004 20130101 |
Class at
Publication: |
428/34.1 |
International
Class: |
B32B 001/02 |
Claims
I claim:
1. A contoured structural member, comprising: at least one
contoured inner layer comprising a composite material; at least one
contoured outer layer comprising a composite material; and wherein
an outer surface of the structural member has a polygonal
shape.
2. The structural member of claim 1, wherein the structural member
has a closed configuration.
3. The structural member of claim 2, further comprising an interior
region defined by an inner surface of the at least one inner
layer.
4. The structural member of claim 3, wherein the interior region is
hollow, partially filled, or completely filled.
5. The structural member of claim 3, wherein the at least one of
the composite materials is formed from a prepreg material.
6. The structural member of claim 5, wherein the prepreg material
comprises a plurality of layers.
7. The structural member of claim 6, wherein the plurality of
layers have a plurality of fibers with an orientation ranging from
0 to about 90 degrees.
8. The structural member of claim 1, wherein the structural member
has at least one end with the at least one initiator not located
near the at least one end.
9. The structural member of claim 1, further comprising a composite
overwrap on a portion of the outer surface of the structural
member.
10. A contoured structural member, comprising: at least one
contoured inner layer comprising a composite material; at least one
contoured outer layer comprising a composite material; and a
composite overwrap on a portion of the at least one contoured outer
layer; wherein an outer surface of the structural member has a
polygonal shape.
11. A contoured structural member, comprising: at least one
contoured inner layer comprising a reinforced resin matrix
material; at least one contoured outer layer comprising a
reinforced resin matrix material; and wherein an outer surface of
the structural member has a polygonal shape.
12. The structural member of claim 11, further comprising a
composite overwrap on a portion of the outer surface of the
structural member.
13. A contoured structural member, comprising: at least one
contoured inner layer comprising a reinforced resin matrix
material; at least one contoured outer layer comprising a
reinforced resin matrix material; and a composite overwrap on a
portion of the at least one contoured outer layer; wherein an outer
surface of the structural member has a polygonal shape.
14. The structural member of claim 13, further comprising a
composite overwrap on a portion of the outer surface of the
structural member.
15. A method for making a contoured structural member, comprising:
providing at least one inner layer comprising a composite material;
providing at least one outer layer over the at least one inner
layer, the at least one outer layer comprising a composite
material; connecting the at least one inner and outer layer to the
at least one inner layer; and providing an outer surface of the
structural member with a polygonal shape.
16. The method of claim 15, including providing the at least one
inner layer by roll wrapping the at least one inner layer over a
substrate.
17. The method of claim 16, including providing the at least one
outer layer by roll wrapping the at least one outer layer over the
at least one inner layer.
18. The method of claim 17, further including removing the
substrate.
19. The method of claim 18, including partially or completely
filling the interior created by removing the substrate.
20. The method of claim 19, further including constraining the at
least one outer layer and reacting any reactable material of the at
least one inner or outer layers prior to removing the
substrate.
21. The method of claim 20, including constraining the at least one
outer layer by roll wrapping at least one layer of a shrink-wrap
material over the at least one outer layer.
22. The method of claim 21, including removing the at least one
layer of the shrink-wrap material after the reaction.
23. The method of claim 20, further including providing a plurality
of pressure distributors over the at least one outer layer while
constraining the outer layer.
24. The method of claim 23, wherein the plurality of pressure
distributors provides the outer surface with the polygonal
shape.
25. The method of claim 15, further including providing an overwrap
over a portion of the at least one outer layer.
26. The method of claim 25, including providing the overwrap by
roll wrapping a composite material over said portion.
27. The method of claim 25, further including radially cutting the
structural member along the portion containing the overwrap.
28. A method of making a contoured structural member, comprising
providing at least one inner layer comprising a reinforced resin
matrix material; providing at least one outer layer over the at
least one inner layer, the at least one outer layer comprising a
reinforced resin matrix material; providing an overwrap over a
portion of the at least one outer layer; connecting the at least
one inner and outer layer to the at least one inner layer; and
providing an outer surface of the structural member with a
polygonal shape.
29. A method of making a contoured structural member, comprising
roll wrapping at least one inner layer comprising a reinforced
resin matrix material over a substrate; roll wrapping at least one
outer layer over the at least one inner layer, the at least one
outer layer comprising a reinforced resin matrix material; roll
wrapping an overwrap over a portion of the at least one outer
layer; connecting the at least one inner and outer layer to the at
least one inner layer; and providing an outer surface of the
structural member with a polygonal shape.
30. A contoured structural member made by the method comprising:
providing at least one inner layer comprising a composite material;
providing at least one outer layer over the at least one inner
layer, the at least one outer layer comprising a composite
material; connecting the at least one inner and outer layer to the
at least one inner layer; and providing an outer surface of the
structural member with a polygonal shape.
31. A contoured structural member made by the method comprising:
providing at least one inner layer comprising a reinforced resin
matrix material; providing at least one outer layer over the at
least one inner layer, the at least one outer layer comprising a
reinforced resin matrix material; providing an overwrap over a
portion of the at least one outer layer; connecting the at least
one inner and outer layer to the at least one inner layer; and
providing an outer surface of the structural member with a
polygonal shape.
32. A contoured structural member made by the method comprising:
roll wrapping at least one inner layer comprising a reinforced
resin matrix material over a substrate; roll wrapping at least one
outer layer over the at least one inner layer, the at least one
outer layer comprising a reinforced resin matrix material; roll
wrapping an overwrap over a portion of the at least one outer
layer; connecting the at least one inner and outer layer to the at
least one inner layer; and providing an outer surface of the
structural member with a polygonal shape.
Description
REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. provisional
patent application No. 60/216,636, the entire disclosure of which
is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to structural members and
methods for making the same. In particular, the present invention
relates to contoured composite parts and methods for making the
same.
BACKGROUND OF THE INVENTION
[0003] In recent years there has been an increasing emphasis on the
use of lightweight composite materials. One application, for
example, has been their use to improve the efficiency of motor
vehicles. To that end, the United States Government and the U.S.
Council for Automotive Research (USCAR)--which represents Daimler
Chrysler, Ford, and General Motors have partnered to form the
Partnership for a New Generation of Vehicles (PNGV). One goal of
PNGV is to develop technology, such as composite technology, that
can be used to create environmentally friendly vehicles with up to
triple the fuel efficiency, while providing today's affordability,
performance and safety. For example, PNGV wants to improve the fuel
efficiency of today's vehicles from about 28 miles per gallon (mpg)
to about 83 mpg and a 40-60% decrease in the present curb weight
(3200 pounds).
[0004] One method to improve the fuel efficiency is to decrease the
weight of today's vehicles and use lighter weight materials. The
materials used in today's vehicles, such as steel and aluminum, are
quite heavy relative to composite materials, but have been
necessary to provide sufficient structural properties, including
tensile, compression, flexural, interlaminar shear, and in-plane
shear strengths and other mechanical and material properties, to
meet vehicle design requirements.
[0005] Many other applications of lightweight composites have been
made to supplement or replace the use of structural materials, such
as steel, cast iron, and aluminum. These include buildings,
bridges, recreational vehicles, aerospace, defense, and sporting
goods, as well as many other applications.
[0006] Composites are a mixture or combination, on a macro scale,
of two or more materials that are solid in the finished state, are
mutually insoluble, and differ in chemical nature. Types of
composites include laminar, particle, fiber, flake, and filled
composites. Composites, however, often have not had the combination
of structural properties mentioned above and/or low cost necessary
to promote their widespread use in motor vehicle and other
applications.
[0007] Despite their lack of structural strength, some composite
materials have been employed in vehicle manufacturing. For example,
laminated composite tubes above have been used as structural
members in vehicles as well as other structures. Typically, the
tube is generally straight over its length, e.g., the radius
remains constant along the length of the tube. As well, the tubes
are generally circular in cross-section. See, for example, U.S.
Pat. Nos. 4,128,963, 4,946,721, 4,968,545, 5,061,533, Re35,081,
5,348,052, 5,447,765, 5,437,450, 5,499,661, 5,579,809, 5,624,115,
and 5,725,920, the disclosures of which are incorporated herein by
reference. Such structural members, however, have been typically
limited to the structures described above and so their end-use and
applications have been quite limited.
SUMMARY OF THE INVENTION
[0008] The present invention provides contoured composite
structural members and methods for making the same. The contoured
structural members comprise composite materials and the contoured
structure can be provided by tube rolling (or roll wrapping) the
composite materials together and then, if necessary, bonding them
or connecting them. The outer surface of the structural member can
be provided with a polygonal shape during the process of
manufacturing. With a contoured structure and an outer polygonal
shape, applications for the structural members of the present
invention are increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1-16 are views of structural members and methods of
making the same according to the present invention. FIGS. 1-16
presented in conjunction with this description are views of only
particular--rather than complete--portions of the structural
members and methods of making the same.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The following description provides specific details in order
to provide a thorough understanding of the present invention. The
skilled artisan, however, would understand that the present
invention can be practiced without employing these specific
details. Indeed, the present invention can be practiced by
modifying the illustrated structural member and method and can be
used in conjunction with apparatus and techniques conventionally
used in the industry.
[0011] FIG. 1 illustrates one contoured structural member--a
tubular member with a substantially circular
cross-section--according to the present invention. In the context
of the present invention, a "contoured" structural member is any
shape, size, or configuration where at least one portion of the
outer or inner periphery of such member is substantially non-flat,
including curved, geometric or irregular. Preferably, the contoured
structural members have a closed surface configuration, such as a
surface that facilitates their manufacture as explained below. In
the context of the present invention, a "closed" structural member
is one having any shape, size, or configuration where at least one
portion of the surface (inner and/or outer) of such member is a
substantially closed or substantially continuous. Examples of a
closed configuration include a tubular, substantially spherical,
polygonal, conical, or other similar shape, as well as those
illustrated and described herein.
[0012] The structural members of the present invention may have a
cylindrical or a non-cylindrical configuration such as cones,
pyramid, pods, hemispheres or spheres. The structural members of
the present invention may also have a circular or a non-circular
cross-section such as rectangular, square, hexagonal, octagonal, or
the like. They may also comprise very irregular, non-closed,
substantially planar surfaces. Indeed, the structural members of
the present invention could have any complex contoured shape or
combination of contoured shapes.
[0013] In FIG. 1, tubular structural member 2 comprises inner
section or portion 4, optional intermediate portion or section 6,
outer section or portion 8, and optional core region 10. Inner
portion 4, outer portion 8, and optional core region 10, can be
made of any suitable composite material as described below. Core
region 10 is located in an inner section of structural member 2
and, as described below, is about the size of the substrate or
mandrel used in forming the structural member. Core region 10 can
be of any suitable size, shape, or configuration depending
primarily on the removable mandrel(s) in the manufacturing process
used to make structural member 2, the configuration of structural
member 2, and the desired end application of structural member
2.
[0014] Core region 10 may be hollow, but may optionally be
partially or completely filled with any desired core material such
as foam, plastic, conducting or insulating materials, metals and/or
the like. Core region 10 containing the core material may be a
structural element. The core material may also be added after
structural member 2 is formed, or formed integrally into the
structure. If the core material is added after the formation of
structural member 2, it may be attached to structural member 2
using an adhesive or other suitable bonding means known in the
art.
[0015] The materials for inner section 4, optional intermediate
section 6, and outer section 8 can be the same or different
materials. Preferably, inner portion 4 optional intermediate
portion 6, and outer portion 8 comprise the same material. In one
aspect of the invention, the materials for the inner or outer
portions comprise any suitable reinforced resin matrix material
(RRMM), which is a resin matrix material (RMM) with continuous or
discontinuous reinforcement material embedded in the resin matrix.
In one aspect of the invention, the RMM is a organic resin matrix
material (ORMM). See, for example, U.S. Pat. Nos. 5,725,920 and
5,309,620, the disclosures of which are incorporated herein by
reference.
[0016] In one aspect of the invention, the ORMM can be a thermoset
resin. Thermoset resins are polymeric materials which set
irreversibly when heated. Examples of thermoset resins include
epoxy, bismeleimide, polyester, phenolic, polyimide, melamine,
xylene, urethane, phenolic, furan, silicone, vinyl ester, and alkyd
resins, or combinations thereof. The thermoset resins can contain
various additives as known in the art, such as cross-linking
agents, curing agents, fillers, binders, or ultraviolet inhibitors.
Preferably, epoxy, vinyl ester, or polyester resins are employed as
the thermoset resin in the present invention.
[0017] In another aspect of the invention, the ORMM can be a
thermoplastic resin matrix material. Thermoplastic resins are
polymeric materials which do not set irreversibly when heated,
e.g., they soften when exposed to heat and then return to their
original condition when cooled. Examples of thermoplastic resins
include polypropylene, polyethelene, polyamides (nylons),
polyesters (PET, PBT), polyether ketone (PEK), polyether ether
ketone (PEEK), polyphenylene sulfide (PPS), polyphenylene oxide
(PPO) and its alloys, and polyvinyl resins, or combinations
thereof. The thermoplastic resins can contain various additives as
known in the art, such as cross-linking agents, curing agents,
fillers, binders, or ultraviolet inhibitors. Preferably, polyamides
(nylons), polyester, polycarbonate and polypropylene resins are
employed as the thermoplastic resin in the present invention.
[0018] The material used to reinforce the RMM of the present
invention can be in any form which reinforces the resin matrix.
Examples of reinforcement forms include unidirectional tape,
multidirectional tapes, woven fabrics, roving fabrics, matt
fabrics, preforms, fibers, filaments, whiskers, and combinations
thereof. The type of material used to reinforce the RMM can be any
type serving such a reinforcing function. Preferably, the form of
the reinforcement materials for the resin matrix is a fiberous
material, such as continuous or discontinuous fibers. Examples of
materials that can be employed in the present invention include
glass-s, glass-e, aramid, graphite, carbon, ultrahigh molecular
weight polyethylene, boron, silicon carbide, ceramic, quartz,
metals, isotropic metals (aluminum, magnesium and titanium), metal
coated organic fibers, CAMP, hybrids of these fibers, or
combinations of these fibers. See, for example, U.S. Pat. No.
6,117,534, the disclosure of which is incorporated herein by
reference.
[0019] In yet another aspect of the invention, non- or
partially-cured composite materials are used as the material for
the inner and/or outer sections. Composites are a mixture or
combination, on a macro scale, of two or more materials that are
solid in the finished state, are mutually insoluble, and differ in
chemical nature. Any composites known in the art such as laminar,
particle, fiber, flake, and filled composites can be employed in
the invention. The non- or partially-cured composite materials are
a ORMM (thermoset or thermoplastic resin) reinforced with a
continuous fiber.
[0020] Preferable composite materials used for inner section 4 and
outer section 8 include B-stage prepreg materials typically in the
form of sheets or laminates, which can be formed by impregnating a
plurality of fiber reinforcement tows with a formulated resin.
Methods of making B-stage prepreg sheets and the sheets themselves
are well known. See, for example, those sheets described in U.S.
Pat. No. 4,495,017, the disclosure of which is incorporated herein
by reference. When cured, prepreg materials are generally stronger
and stiffer than metals while providing greater resistance to
fatigue, chemicals, wear and corrosion. Preferable reinforcement
for prepregs include aramids, glass materials, nickel carbide,
silicone carbide, ceramic, carbons and ultra-high molecular weight
polyethylene, or a combination thereof. See, for example, U.S. Pat.
Nos. 4,968,545, 5,102,723, 5,499,661, 5,579,609, and 5,725,920, the
disclosures of which are incorporated herein by reference. Carbon,
glass, metals and especially isotropic metals like aluminum,
magnesium and titanium, metal-coated organic fibers, and aramid
fibers, or a combination thereof, can also be employed as the
fibers. See, for example, U.S. Pat. Nos. 5,601,892 and 5,624,115,
the disclosures of which are incorporated herein by reference.
Preferably, carbon fibers, glass fibers, or aramid fibers and more
preferably Kevlar 29 or 49 fibers are employed in the present
invention.
[0021] The fiber volume in the prepregs may be varied so as to
maximize the mechanical, electrical, and thermal properties. See,
for example, U.S. Pat. No. 5,848,767, the disclosure of which is
incorporated herein by reference. High fiber volume parts are
stiffer and, in the case of thermally conductive fibers, the parts
are more thermally conductive. Fiber volumes in the present
invention can range from about 5% to about 95%, and preferably
range from about 50% to about 65%. The fibers of the prepregs may
be oriented within the prepreg material in any desired direction as
known in the art, such as about 0 to about 90 degrees, including
equal numbers of fibers balanced in opposing directions. See, for
example, U.S. Pat. No. 4,946,721, the disclosure of which is
incorporated herein by reference.
[0022] In yet another aspect of the invention, sheet molding
compounds (SMCs) can be used as the materials for the inner or
outer portion. SMCs are sheets made up of B-stage thermoset resin
reinforced with a discontinuous fiber. SMCs are fully formulated
ORMM compounds having discontinuous fiber reinforcement materials
which are typically formed into sheet, ply, or laminate without
additional preparation. See, for example, U.S. Pat. No. 6,103,032,
the disclosure of which is incorporated herein by reference. The
resins that can be used in the SMCs of the present invention
include any of the thermoset resins listed above. Preferably,
polyester vinyl esters or epoxy resins are employed as the resin in
SMCs of the present invention. The fibers that can be used in the
SMCs of the present invention include any of those listed above.
Preferably, glass, carbon, or aramid fibers, and more preferably
Kevlar 29 or 49 fibers can be used as the fibers in the SMCs. The
fiber volume in the SMC may also be varied so as to maximize the
mechanical and thermal properties.
[0023] With an unsaturated resin system as its base, SMCs
incorporate other materials for desirable processing and molding
characteristics and optimum physical and mechanical properties,
such as mechanical strength, impact resistance, stiffness, and
dimensional stability. These incorporated materials include
polymers, fibers for reinforcement, resins, fillers, initiators to
promote polymerization, viscosity agents, lubricants, mold release
agents, catalysts, thickeners, pigments, polyethylene powders,
flame retardants, ultraviolet absorbing agents, and other
additives. Each of the additives can provide important properties
to the SMC, either during the processing or molding steps or in the
finished parts, and can be incorporated in the SMCs of the present
invention.
[0024] In one aspect of the invention, inner section 4, optional
intermediate section 6, and outer section 8 contain at least one
layer of such ORMM materials. One layer is sufficient to form the
respective inner or outer section and provide the desired
structural characteristics for structural member 2. Additional
layers can be added to improve the strength, stiffness, or other
physical characteristics of structural member 2. It is possible to
use a single layer with fibers having complementary orientations.
It is preferred, however, to use a plurality of layers with
complementary orientations to balance intrinsic stresses in the
layers that make up the sections that result when, as described
below, the B-stage materials are fully cured. To be complementary,
the fibers in successive layers should be symmetric and balanced
(e.g., by having the fibers offset from the sheet axis by equal and
opposite amounts from one layer to another) as shown in FIG. 2. The
fibers can also be oriented to meet the design parameters of the
component into which they are being incorporated, e.g., to optimize
the structural strength against the expected load. The fibers could
be oriented at any suitable angle, including at angles ranging from
about 0 to about 90 degrees, including in .+-.15, .+-.30, .+-.45,
.+-.60, and .+-.75 degrees, or as otherwise known in the art. See,
for example, U.S. Pat. Nos. Re. 35,081 and 5,061,583, the
disclosures of which are incorporated herein by reference.
[0025] The configuration of inner portion 4 optional intermediate
section 6, and outer portion 8 can vary within structural member 2.
For example, the materials used for the composite, the fiber
orientation, and the curvature, thickness, shape and other
characteristics of the inner and/or outer portions (4, 8) can
differ along the length and width of structural member 2. See, for
example, U.S. Pat. No. 5,718,212, the disclosure of which is
incorporated by reference.
[0026] The structural member of the present invention may, if
desired, have additional layers or portions on the outside of outer
portion 8. In one example, a layer of metal, insulation, another
composite material, or honeycomb core material may be placed over
outer portion 8. Numerous additional portions or layers, including
similar or different composite materials, could be added in a
similar manner. In addition, at least one structural component,
such as a bracket, coupler, cap, or the like could be located on
the end(s) of structural member 2.
[0027] The structural member of the present invention may have any
substantially non-flat contour or configuration. FIG. 4 illustrates
several such configurations. In one aspect of the invention, the
structural members of the present invention can be configured with
any contoured shape known in the art. The contoured shapes can have
any combination of inner or outer shapes, inner and outer
thickness, and inner or outer radii.
[0028] In preferred aspect of the invention, the structural members
of the present invention have the contoured shapes illustrated in
FIG. 12. The preferred contoured shapes have a thickness and/or a
radius that varies--either regularly or irregularly--along the
length of the structural member. For example, referring to FIG. 12,
the structural member 2 comprises a first portion 41 with a first
diameter, a second portion 42 with a second diameter, and a third
portion 43 with a third diameter. As another example, as
illustrated in FIG. 13, the structural member 2 comprises a first
portion 46 with a first thickness, a second portion 47 with a
second thickness, and a third portion 48 with a third
thickness.
[0029] In another preferred aspect of the invention, the shape of
the structural member has a shape other than substantially
circular. Examples of such shapes include rectangular, hexagonal,
octagonal, polygonal, etc . . . Making the tube with polygonal
shape--such as a hexagon--provides several flat surfaces on the
inner or outer surface of the structural member, which becomes
important when bonding the surface of the structural member to
another member, such as a metal end piece. An interference is
created between the surface of the other member (metal end piece)
and the surface of the structural member, supplying torsional
resistance when either the structural member or the end piece is
subjected to a load. The larger the interference, the more
resistance is given to the torsion, separate from the resistance
provided by the bond surface. The amount of interference is
proportional to the torsional resistance, so increasing the
diameter or decrease the number of polygon flats thereby increases
the resistance to torsion, as is depicted in FIG. 14.
[0030] Creating a polygonal shape, however, creates a secondary
loading condition on the structural member. This loading condition
is usually localized near the bond surface and can easily be great
enough to explode the structural member from the inside. To protect
against such a problem, that area of the structural member 2 is
"overwrapped" with a composite collar comprising of fibers which
are oriented around the circumference of the structural member.
This prevents the structural member from exploding, while not
adding much weight. The overwrap is located over the entire joint
area with some extension past the joint to help with stress
concentrations.
[0031] The optimum number of sides of the polygonal shape depends
on the individual design. The more sides used, the less
interference there will be and the less torsional resistance. Yet
increasing the number of polygonal sides moves closer to a round
shape. So reducing the optimum joint strength to weight ratio will
also increase the optimum tube strength to weight ratio. The number
of composite plies used in the overwrap also depends on the design
and the internal pressure due to the torsion and the resistance to
internal pressure. Obviously a thicker tube would normally resist
more internal pressure and require less number of overwrap plies.
But then it may have a significantly larger internal pressure due
to a large torsional load. As with every design, the optimum design
will be the one which is the lightest for it's given strength and
stiffness.
[0032] The structural members of the present invention can be made
by any suitable process that provides the desired structure.
Suitable process for making the composite layer(s) include any
processes known in the art, such as thermoforming, bladder or resin
transfer molding, or inflatable mandrel processes, as described in
U.S. Pat. Nos. 5,225,016, 5,192,384, 5,569,508, 4,365,952,
5,225,016, 5,624,519, 5,567,499, and 5,851,336, the disclosures of
which are incorporated herein by reference. Another suitable
process is a vacuum bagging process, such as described in U.S. Pat.
No. 5,848,767, the disclosure of which is incorporated herein by
reference. Other suitable processes are a filament winding process
or sheet or tube rolling (also known as roll wrapping). See, for
example, U.S. Pat. Nos. 5,632,940, 5,437,450, 4,365,952, 5,624,529,
5,755,558, 4,885,865, 5,332,606, 5,540,877, 5,840,347, and
5,914,163, the disclosures of which are incorporated herein by
reference.
[0033] In the filament winding process, filaments of the desired
material are dispersed in a matrix of binder material and wound
about any suitable substrate, such as a mandrel assembly. Any
suitable mandrel or mandrel assembly, including those described in
U.S. Pat. Nos. 5,795,524, 5,645,668, 5,192,384, 5,780,075,
5,632,940, 5,817,203, and 5,914,163, the disclosures of which are
incorporated by reference, can be employed in the present
invention.
[0034] In one aspect of the invention, the substrate or mandrel
must have sufficient strength, desired shape, and be able to
withstand the processing conditions for making the structural
member. Suitable mandrels include those made of metals like steel
and aluminum, polycarbonate, thermoplastic, or RRMM materials. The
mandrels may be solid or hollow. The mandrel or substrate should
have a shape generally corresponding to the desired shape (core
region 10) of structural member 2, e.g., the outer surface of the
mandrel should have a shape corresponding to the inner surface of
the inner portion 4.
[0035] The filaments are wound over the mandrel and are
reciprocally displaced relative to the mandrel along the
longitudinal or winding axis of the mandrel to build portion 4.
Additional portions, structures, or layers, such as additional
metal or composite layers, can be added as described above or as
known in the art.
[0036] Preferably, the present invention employs a tube rolling
(also known as roll wrapping) process for making the structural
member of the present invention. One exemplary tube rolling process
is illustrated in FIG. 5. The tube rolling process employs discrete
sheet(s) (or plies or laminates) of the desired composite material
rather than filaments. The sheet(s) is interleaved, wrapped, or
rolled over a mandrel assembly such as at least one mandrel 20. If
desired, a release film can be applied to the mandrel prior to
rolling any materials thereon. When more than one sheet is
employed, the sheets can be stacked as illustrated in FIG. 2--prior
to or during the rolling process--by hand or by any suitable
mechanical apparatus, with the fibers of the composite material
oriented in the desired orientation. After forming inner portion 4,
the roll wrapping process continues to apply the material of outer
portion 8. Further details about roll wrapping processes are
described in Engineered Materials Handbook, Volume 1: Composites,
ASM International, pp. 569-574 (1987), the disclosure of which is
incorporated herein by reference.
[0037] Additional layers or materials can be added over outer
portion 8, if desired, in a similar manner using any of the above
processes. By adding additional composite plies or additional
composite materials at this stage, the structural members
illustrated in FIGS. 12 and 13 can be created. For example, the
"base" structural member illustrated in FIG. 13, can be made by the
above process. Then, additional plies (or sheets) of the desired
material can be added by wrapping in the desired areas to obtain
the varying the additional thicknesses. In a similar manner,
additional plies can be wrapped to create the overwrap described
above.
[0038] The layers of the individual portions (inner, intermediate,
and outer) can be cut and/or patterned such that when roll wrapped,
the ends of individual sheet(s) substantially abut when rolled,
thereby forming a butt joint 30. Preferably, the butt joint formed
by the ends of any single sheet is staggered from the butt joint
formed by the ends of an adjacent sheet, as illustrated in FIG.
6.
[0039] Inner portion 4 and outer portion 8 may be formed using
different methods. For example, inner portion 4 can be formed by
filament winding and outer portion 8 by roll wrapping, or vice
versa. In this aspect of the invention, inner portion 4 may be
fully cured prior to the application of intermediate portion 6.
Similarly, inner portion 4 and intermediate portion 6 may be
applied and cured together prior to the application of outer
portion 8. Other methods known in the art, such as those described
above, could also be combined with roll wrapping to make the
structural members by performing discrete steps by different
methods. For example, inner portion 4 could be formed using the
filament winding process, intermediate portion 6 and outer portion
8 could be formed using the roll wrapping process, and then this
intermediate structure could be constrained using a vacuum bagging
process.
[0040] If desired, a bonding agent can be placed between successive
layers of portions 4 and/or 8. The bonding agent can be placed on
selected areas only, or in a pattern such as in rows and/or
columns, or over entire areas of the layer(s)/portion(s). Any
suitable agent which helps bond the layers and is compatible with
all of the processes employed to make structural member 2 can be
employed, including glues, curing agents, adhesive materials, or a
combination thereof. See, for example, U.S. Pat. No. 5,635,306, the
disclosure of which is incorporated herein by reference. The
bonding agent can be applied by hand or mechanical apparatus prior
to, during, or after the assembly of the respective portion on the
substrate.
[0041] Where portions 4 and 8 are successively layed up in an
uncured (e.g. B-stage state), the structure has outer portion 8
overlying inner portion 4, which overlies the mandrel. If necessary
to better bond and connect inner portion 4 and outer portion 8
together, the intermediate structure formed by these portions can
be constrained. The intermediate structure can be constrained by
applying a suitable compressive force. This can be done using any
suitable means including compressive dies or molds, vacuum bagging,
or by using a suitable constraining means, e.g., by placing it in a
plastic or metal mold, or by applying a suitable shrink-wrap
tape(s) 22 or tube made of nylon, silicone, or polypropylene.
During the curing process described below, the compressive means
(e.g., the shrink-wrap tape or tube) applies suitable compressive
force by physical or chemical change so that the materials of
structural member 2 contact each other. When the RMM is used in the
inner and/or outer portion of the present invention, the
compressive force squeezes out excess resin during this curing
process. See, for example, U.S. Pat. Nos. 5,600,912 and 5,698,055,
the disclosures of which are incorporated herein by reference.
[0042] Moreover, if it is still necessary to better bond and
connect the materials in the intermediate structure, they can
undergo a suitable chemical reaction. For example, when inner
portion 4 and/or outer portion 8 comprise a curable material (e.g.,
B-stage epoxy prepreg), the intermediate structure can be cured by
any suitable means 24, such as an oven curing by applying heat
and/or pressure or using an ultraviolet (u.v.) or microwave curing.
The necessary heat and/or pressure depend on the size of the
mandrel assembly and the materials used in structural member 2.
During the curing process, the shrink-wrap tape or tube applies
suitable compressive force. When the RMM is used in the inner
and/or outer portion of the present invention, the compressive
force squeezes out excess resin during this curing process.
[0043] The above process can be modified for structural members not
having a substantially circular cross-section, including those with
outer diameters having at least one flat area or area where the
degree of curvature is substantially different from other surfaces
of structural member 2. Examples of such structural members are
illustrated in FIG. 4. As illustrated in FIG. 7, where the outer
diameter has at least one relatively flat area, the shrink-wrap
material (and accompanying compressive force) applied to the
intermediate structure may not be uniform. Thus, bonding and
connecting the materials to one another may not be uniform and,
therefore, might impair the integrity of structural member 2. To
more uniformly bond and connect such materials, at least one
pressure distributor 26 is placed over the relatively flat areas of
outer portion 8 prior to applying the shrink-wrap material. The
pressure distributors "distribute" the applied compressive force
more evenly to such flat areas, allowing a more uniform compressive
force to all areas of the intermediate structure.
[0044] Any suitable shape of pressure distributors which evenly
distribute the applied compressive force to the intermediate
structure can be employed in the present invention. Exemplary
shapes of the pressure distributors include substantially
semicircular shapes (which provide a substantially circular outer
surface) and T-shaped distributors where the flat end of the "T"
abuts (and matches in size) the flat area of the intermediate
structure and the long-end of the "T" extends outwards. Other
shapes and configurations, including single components rather than
plural components, could be employed provided they evenly
distribute the compressive force over the flat area(s). For the
structural member 2 like the one illustrated in FIG. 4,
substantially semicircular pressure distributors 26 are depicted in
FIG. 7. The pressure distributors of the present invention can be
made of any suitable material that will maintain its shape when
subjected to the compressive force, such as aluminum, steel, and
silicone. Preferably, aluminum is employed as the material for the
pressure distributor.
[0045] The shrink-wrap material can be placed under and/or over the
pressure distributor(s). The shrink-wrap materials underlying the
pressure distributors pressurize the comers, as well as keeping the
pressure distributors from sticking to the intermediate structure.
The shrink-wrap materials overlying the pressure distributors
pressurize the flat areas.
[0046] The above process can be also be modified for structural
members where the inner and outer portion do not have the same
shape, such as those depicted in FIG. 11. Any suitable process
modification which manufactures differently-shaped inner and outer
portions can be employed in the present invention. The following
two modifications to the above process demonstrate this concept.
Other modifications could be envisioned, even though not
demonstrated below.
[0047] First, the inner portion can have a substantially circular
cross-section and the outer portion a non-circular cross-section.
In such an instance, and as shown in FIG. 8, the process for making
a circular-shaped structural member is followed as described above.
To change the shape of the outer portion, a number of pressure
distributors are placed over the circular-shaped outer portion
prior to the constraining and curing stages. The number of pressure
distributors used corresponds to the number of flat sides desired,
e.g., four for a square, six for a hexagon, etc . . . The process
as noted above is then continued for the constraining and curing
stages. During the constraining and curing process, the circular
outer shape is changed to flat sides of the desired polygonal shape
by the pressure exerted via the pressure distributors.
[0048] Second, the inner portion can have a substantially polygonal
shape (i.e., hexagon) and the outer portion a substantially
circular shape. In this aspect of the invention as depicted in FIG.
9, the process for making a hexagonal-shaped structural member is
followed as described above. To change the shape of the outer
portion, the pressure distributors that are normally placed over
the outer portion prior to the constraining and curing stages are
omitted. Thus, the square-shaped outer portion is just wrapped with
the constraining means. The process as noted above is then
continued for the constraining and curing stages. During the
constraining and curing process, the outer shape is changed to a
substantially circular shape by the pressure exerted via the
constraining means.
[0049] When used, the constraining means are then removed from the
intermediate structure. For the plastic or metal mold, the mold is
opened and removed. The shrink-wrap tape or tube may have reacted
during the curing process to form a thin shell and, if desired, may
be removed by hand or by a mechanical apparatus. When used, the
pressure distributors are also removed.
[0050] In another aspect of the invention, the constraining means
can be left on the outer portion either temporarily or permanently.
For example, the shrink-wrap tape could be left on the structural
member in the form as a thin shell for protection during shipping
and then removed later. In another example, the shrink-wrap tape
could be left on the structural member permanently as a protective
coating.
[0051] Through the constraining and curing processes described
above, the inner portion and the outer portion are chemically
attached and/or or connected to the intermediate portion.
Preferably, the materials of the inner and outer portion both
chemically bond to the material of the intermediate portion, thus
forming a substantially permanent physical bond.
[0052] Next, the substrate or mandrel may be removed from
structural member 2 to form core region 10. The mandrel may be
removed by any suitable process, including any known in the art
which safely removes the mandrel without adversely impacting
structural member 2, such as those disclosed in U.S. Pat. Nos.
5,900,194 and 5,306,371, the disclosures of which are incorporated
herein by reference. If desired, core region 10 can be filled by
any desired material as known in the art.
[0053] The mandrel can be either a removable mandrel or an integral
mandrel. A removable mandrel is a mandrel that, as described above,
is used in the roll wrapping process and then removed to create
interior 10. An integral mandrel is a mandrel which becomes part of
structural member 2 and is not removed. Thus, the mandrel remains
in core region 10 and becomes a part of structural member 2.
[0054] When using an integral mandrel, the structural member 2 and
the process for making that member are modified from the above
description. In this aspect of the present invention, the
intermediate portion is provided over the integral mandrel, and
then the outer portion is provided over the intermediate portion.
The structural member then follows the processing described above,
with the exception that the integral mandrel is not removed. Thus,
the integral mandrel can serve as the inner portion. If desired, an
inner portion could still be included over the integral mandrel,
yielding a structural member with an integral mandrel, an inner
portion, an intermediate portion, and an outer portion.
[0055] Once formed, the structural members of the present invention
can be modified or cut for any desired use. For example, the
structural members illustrated in FIGS. 5 and 7-9 have been cut in
half along its length to provide two structural members. Likewise,
the structural members could be cut along its length to provide any
number of members with the desired length(s). Numerous shapes and
configurations can be made using by cutting along any dimension of
the structural members, especially when combined with the broadest
aspects of the processes of the present invention. A few examples
of the shapes and configurations obtained by cutting the structural
members in the above manner are shown in FIG. 10.
[0056] In a preferred aspect of the invention, and as illustrated
in FIG. 15, selected portions of the outer portion 8 are provided
with an overwrap 6. The overwrap can be provided by any means known
in the art. Preferably, the overwrap is provided by selecting the
desired size (and thickness) of the plies 50 needed to form the
overwrap and then roll wrapping these plies 50 over the selected
portions of the outer portion 8. The structural member can then be
cut radially in the middle of the overwrap, thereby providing two
or more structural members with overwrapped portions on one--or
both--of their ends.
[0057] After cutting the structural members of the present
invention, additional structural components can be added. Any
structural component known in the art can be added to the modified
structural member, such as a bracket, fastener, coupler, cap, or
the like. In a preferred aspect of the invention, the structural
members have a metal end piece bonded in an the end thereof,
thereby creating a structural part for torque type application
which can be used as a drive shaft, half shaft, or likewise.
[0058] Further modifications--other than just cutting--can be made
to the structural members of the present invention. For example,
channels, holes, patterns, and similar modifications can be made in
the inner or outer surface of the structural member for many
reasons, such as to attach a structural component, modify the
surface properties, or a similar purpose.
[0059] Roll wrapping is the preferred method for making the
structural members of the present invention. The other methods
described above, however, could be combined with roll wrapping to
make the structural members by, in one aspect of the invention,
performing discrete steps by different methods. For example, inner
portion 4 could be formed using the filament winding process, the
intermediate portion 6 and the outer portion 8 could be formed
using the roll wrapping process, and then the intermediate
structure could be constrained using the vacuum bagging
process.
[0060] The structural member of the present invention has numerous
uses such as a tie, torsion-bar, tube, beam, column, cylinder and
the like and can be used in numerous industries. Primarily, the
structural member can be used whenever a lightweight, strong,
cylindrical object is required. The structural member of the
present invention can be used in the automotive, transportation,
aerospace, and defense industries in applications such as airplane
components, vehicle components such as tracks, trains, shipping
containers, defense-related applications, recreational applications
such as bikes, sail masts, shafts for golf clubs and racquets, or
commercial applications such as bridges and buildings.
[0061] The following non-limiting examples illustrate the present
invention.
EXAMPLE 1
[0062] A hollow, cylindrical structural member with a circular
cross-section outside and hexagonal inside was made according to
following process. A thin coat of a release material (Frekote 700NC
or Axel EM606SL/SP) was applied to a 0.3125" radius hexagonal
aluminum mandrel with six equilateral outer sides of 0.3125 inch
and a length of 56 inches.
[0063] Nine pairs of B-stage prepreg laminate sheets (18 individual
sheets) containing anisotropic carbon fibers were cut to a length
of about 2.25 to about 2.84 inches in width and about 52 inches in
length. The sheets each have different widths according to their
location in the lay-up on the mandrel, e.g., each layer
sufficiently wide to form closely-spaced butt joints when the layer
is wrapped around the mandrel. The individual laminate sheets were
then overlaid so the fibers in successive sheets were symmetric and
balanced at angles of .+-.45 degrees. The air between the stacked
sheets was removed by using a roller or other suitable device. The
stacked prepreg sheets were then roll wrapped by hand around the
aluminum mandrel with a butt joint.
[0064] A first set of two strips of unidirectional tape containing
anisotropic carbon fibers were cut to a length of about 10 inches
and about 1 inch in width. A second set of two more strips of
unidirectional tape containing anisotropic carbon fibers were cut
to a length of about 10 inches and about 2 inches in width. The
first set of strips were wrapped on the prepreg sheets to create an
outer set of overwraps, leaving about 0.5 inch from each end
without any overwrap (e.g., the middle of the overwrap is located 1
inch from the end). Similarly, the second set of strips were
wrapped on the prepreg sheets to create an inner set of overwraps
located so the middle of the overwrap is about 17.5" from the ends.
Given the length of the overwraps and the outer circumference of
the prepreg layers on the mandrel, both the inner and outer sets of
overwrap contained five layers.
[0065] Next, the resulting intermediate structure was
shrink-wrapped. One layer of polyethylene-based shrink-wrap tape
was roll wrapped by a shrink-wrapping machine using gauge number
150 on the resulting structure. Another layer of nylon-based
shrink-wrap tape was then roll wrapped by a shrink-wrapping machine
using gauge number 200.
[0066] After this wrapping process, the final structure was
subjected to a curing process at about 250 degrees Fahrenheit for
about 120 minutes during which the shrink-wrap tapes applied
compressive pressure to the intermediate structure. After this
curing process, the shell (formed by the shrink-wrap tapes during
the curing process) was removed by hand with a knife. The mandrel
was then removed from the center of the tube by hand.
[0067] The half-inch section from each end (with no overwrap) of
the resulting structural member was cut off and discarded. The rest
of the tube was cut into three, substantially equal 17-inch
sections with about a 1" wide overwrap on each end using 0.125 inch
thick diamond saw. Thus, three 17" torque tubes were created with
the following characteristics: a hexagonal inside and circular
outside cross-section, 18 composite layers (or sheets), and 1 inch
overwraps at each end containing 5 composite layers (or
sheets).
[0068] Similar torque tubes were then created. A first group of
torque tubes were created similar to the above process, but having
10, 12, 14, and 16 composite sheets instead of 18 composite sheets.
A second group of torque tubes were created similar to the above
process, but having 3, 10, and 15 composite layers in the overwraps
instead of the 5 composite slayers.
[0069] The torque tubes were subjected to the following torque
test. First, a solid equilateral hexagonal low carbon steel shaft
with about 0.312" sides was cut into one-inch long sections. Half
of section was cleaned with acetone to remove any oil and other
contaminants, sand blasted, and then cleaned again with acetone.
The clean section of a steel shaft was then bonded to a torque tube
using Hysol EA 9430 adhesive, leaving about 0.5 inch section of the
steel shaft exposed. The torque tubes (with inserted steel shaft)
were then oven cured for one hour at 200.degree. F. The torque
tubes with the inserted steel shaft were tested at room temperature
using CDI Torque Wrench (Model Number 6004 CFII). The torque wrench
records only maximum torque between 60 and 600 Ft-Lbs, with an
accuracy of +/-1%.
[0070] The test results are reported in FIG. 16. The results
indicated that the steel shaft broke at different points depending
on the number of composite layers in the tube and the number of
composite layers in the overwrap. Although not reflected in Table
1, generally the torque of any composite shaft depended on the type
of materials used, the radius of tube, polygon shape and size, the
number of layers in the composite tube, the configuration of
composite layup, and the number of overwrap layers.
[0071] Having described the preferred embodiments of the present
invention, it is understood that the invention defined by the
appended claims is not to be limited by particular details set
forth in the above description, as many apparent variations thereof
are possible without departing from the spirit or scope
thereof.
* * * * *