U.S. patent application number 10/994825 was filed with the patent office on 2005-04-28 for shaped contoured crushable structural members and methods for making the same.
This patent application is currently assigned to DELPHI TECHNOLOGIES, INC.. Invention is credited to Obeshaw, Dale Francis.
Application Number | 20050089707 10/994825 |
Document ID | / |
Family ID | 22807863 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050089707 |
Kind Code |
A1 |
Obeshaw, Dale Francis |
April 28, 2005 |
Shaped contoured crushable structural members and methods for
making the same
Abstract
Shaped, contoured crushable structural members and methods for
making the same are described. The contoured structural members
comprise composite or metal materials sandwiching a support or
stabilizing structure. The structural members are made crushable by
incorporating an initiator into the structural members. The
structural member crushes at the location of the initiator by
absorbing the energy of an exerting load. The shaped structure is
provided by bending the generally straight shape of the structural
member. With a shaped, contoured, crushable, and generally non-flat
structure, applications and uses for the structural members of the
present invention are nearly limitless.
Inventors: |
Obeshaw, Dale Francis; (Salt
Lake City, UT) |
Correspondence
Address: |
Michael D. Smith
DELPHI TECHNOLOGIES, INC.
Legal Staff, Mail Code: 480-410-202
P.O. Box 5052
Troy
MI
48007-5052
US
|
Assignee: |
DELPHI TECHNOLOGIES, INC.
|
Family ID: |
22807863 |
Appl. No.: |
10/994825 |
Filed: |
November 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10994825 |
Nov 22, 2004 |
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09900762 |
Jul 5, 2001 |
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6821638 |
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60216636 |
Jul 7, 2000 |
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Current U.S.
Class: |
428/593 ;
428/615 |
Current CPC
Class: |
F16L 9/19 20130101; F16L
7/00 20130101; B29C 70/32 20130101; B32B 3/30 20130101; B62D 29/001
20130101; B32B 15/01 20130101; Y10T 428/12493 20150115; B32B 15/08
20130101; B32B 3/12 20130101; Y10T 428/24165 20150115; B62D 21/15
20130101; B62D 21/00 20130101; B21C 37/154 20130101; B62D 21/09
20130101; B21C 37/15 20130101; B32B 1/08 20130101; B32B 15/04
20130101; B29D 24/002 20130101; Y10T 428/1234 20150115; Y10T
428/1241 20150115; B62D 29/005 20130101; Y10T 428/12375 20150115;
B32B 3/28 20130101; B32B 27/04 20130101; F16L 9/003 20130101; F16L
9/006 20130101; B65H 2701/5114 20130101; B29D 24/004 20130101; B29D
99/0035 20130101; Y10T 428/12361 20150115; F16L 9/02 20130101; B62D
29/004 20130101; Y10T 428/13 20150115; B65H 75/10 20130101; F16L
9/18 20130101; Y10T 428/139 20150115; Y10T 29/53652 20150115; A63B
60/54 20151001; Y10T 428/24149 20150115; B29L 2031/324
20130101 |
Class at
Publication: |
428/593 ;
428/615 |
International
Class: |
B32B 003/12 |
Claims
1. A shaped contoured structural member, comprising: an inner
section containing a continuous plurality of contoured layers
comprising both a layer of a composite material and a layer of a
metal-containing material; an outer section containing a continuous
plurality of contoured layers comprising both a layer of a
composite material and a layer of a metal-containing material; and
at least one intermediate layer having a honeycomb core structure
connecting the inner section and the outer section.
2. The structural member of claim 1, wherein the structural member
has a substantially non-straight configuration.
3. (canceled)
4. (canceled)
5. The structural member of claim 1, wherein the layers of
metal-containing material are layers of metal alloy.
6. The structural member of claim 1, further comprising at least
one initiator.
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 shaped, contoured crushable 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] One way to increase the structural properties of materials,
particularly the torsional or flexural strength, is to make them in
a more structurally efficient form. In one structurally efficient
form, metals like aluminum and steel have been combined with a
supporting structure, such as a honeycomb core material, by
sandwiching the honeycomb between panels of the metal. Examples of
such combinations have been described in U.S. Pat. Nos. 4,291,205,
5,140,913, 5,192,623, 5,635,306, 5,875,596, and 5,899,037, the
disclosures of which are incorporated herein by reference. In
another structurally efficient form, composite materials have been
combined with a supporting structure, such as a honeycomb or foam
structure, by sandwiching the supporting structure between panels
of the composite material. Examples of such combinations have been
described in U.S. Pat. Nos. 5,006,391, 5,195,779, 5,652,039,
5,834,082, 5,848,767, 5,849,122, and 5,875,609, the disclosures of
which are incorporated herein by reference.
[0007] Such combinations, however, have been generally limited to
relatively flat structures and so applications of such materials
have been quite limited. As well, the structural members have not
been able to be shaped or bent into various complex shapes,
including substantially non-straight shapes, necessary to enhance
their end-use.
SUMMARY OF THE INVENTION
[0008] The present invention provides shaped contoured crushable
structural members and methods for making the same. The contoured
structural members comprise composite or metal materials
sandwiching a support or stabilizing structure. The structural
members are made crushable by incorporating an initiator into the
structural members. The structural member crushes at the location
of the initiator by absorbing the energy of an exerting load. The
shaped structure is provided by bending the generally straight
shape of the structural member. With a shaped, contoured,
crushable, and generally non-flat structure, applications and uses
for the structural members of the present invention are nearly
limitless.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1-20, 20A, 21, 21A, and 22-24 are views of structural
members and methods of making the same according to the invention.
FIGS. 1-20, 20A, 21, 21A, and 22-24 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 according to the invention.
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 facilitating 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. In one aspect of the invention, a
contoured structural member is one that has a wall that completely
or substantially circumscribes an interior space, regardless of the
circumferential or peripheral shape of the member.
[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 as described in detail below. The
structural members of the present invention are characterized by
the fact that they are substantially non-flat and thereby
distinguished from known sheet-shaped cored composite
structures.
[0013] In FIG. 1, tubular structural member 2 comprises inner
section or portion 4, optional intermediate section or portion 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.
Optional intermediate portion 6 is a "cored" structure that
attaches to and supports and/or stabilizes the inner and outer
portions.
[0014] 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.
[0015] 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.
[0016] The materials for inner section 4 and outer section 8 can be
the same or different materials. Preferably, inner portion 4 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.
[0017] 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
[0018] 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.
[0019] 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, ultra-high 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] In one aspect of the invention, inner section 4 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 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.
[0026] In yet another aspect of the invention, the materials for
the inner or outer portions can comprise any suitable
metal-containing materials, such as a light or heavy metal or
alloys thereof. Suitable light metals include magnesium, aluminum,
titanium, zinc, molybdenum, or alloys thereof. Suitable heavy
metals include iron, copper, nickel, carbon steel, stainless steel,
alloy steel, tin, or alloys thereof.
[0027] Since metal-containing materials comprise isotropic fibers,
which exhibit similar strength characteristics in all directions,
one layer of the metal-containing material is sufficient to form
the respective inner or outer portion and provide the desired
structural characteristics. Additional layers of the
metal-containing material, depending on cost and structural
considerations, can also be used to give the desired thickness of
the inner or outer portion. Indeed, successive layers of different
metal-containing materials may be employed as the inner and/or
outer portion.
[0028] The configuration of inner portion 4, optional intermediate
portion 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.
[0029] Optional intermediate portion 6 of the structural member 2
of the present invention has any structure which spaces and/or
supports inner portion 4 and outer portion 8, as well as enhances
the structural properties of those two portions when placed there
between. Further, intermediate section 6 can be made of any
suitable material which separates, supports, stabilizes, couples
and attaches inner portion 4 with respect to outer portion 8.
Interposing intermediate section 6 between inner section 4 and
outer section 8 improves the structural properties according to
well-known principles of engineering mechanics and mechanical
engineering of structural member 2 over the properties of a member
comprising only appropriately shaped inner section 4 and outer
section 8 bonded together. Preferably, as illustrated in FIG. 1,
the intermediate portion is substantially contiguous with the outer
surface of inner section 4 and the inner surface of outer section
8, e.g., the intermediate section 6 contacts the inner section 4
and/or the outer section 8 at discrete points over most--if not
all--of their surfaces.
[0030] In one aspect of the present invention, intermediate portion
6 has a ribbed structure (RS), or a structure where any single
member (rib) of that structure extends continuously from a location
proximate the inner (or outer) portion to a location proximate the
outer (or inner) portion. In another aspect of the invention, the
RS is a structure where any rib connects at one end to a location
proximate the at least one layer of the inner (or outer) portion
and the other ends abuts or connects to another rib. Examples of
RSs include corrugated materials, posts, curvilinear materials,
honeycomb cores, and the like. These structures, as well as other
RSs, are illustrated in FIG. 3.
[0031] A RS is advantageous because, for the additional weight
added, the structural properties of the structural member are often
substantially increased. The RSs contain both "ribs" and a large
volume of voids. The "ribs" of the RS enhance the structural
properties of the structural member while the voids are provided to
minimize the weight of the RS. The respective amounts of ribs and
voids present in the RSs used in the present invention depend on
the configuration of the RS selected, e.g., which of those
illustrated in FIG. 3 is selected. Preferably, the amount of voids
should be maximized and the amount of ribs minimized, thereby
giving the minimum weight for the maximum strength, provided the
necessary (or desired) structural properties of the RS or the
structural member is obtained.
[0032] The RSs employed in the present invention can be
incorporated into the structural member in any suitable manner. In
one aspect of the invention, the RS can be incorporated as a
standalone "rib" extending from the at least one layer of the inner
portion to the at least one layer of the outer portion, such as the
configurations illustrated in FIG. 3. In another aspect of the
invention, the rib can be connected to a supporting sheet(s) or
another rib(s) where the sheet(s) or other rib(s) itself is
connected to the at least one layer of the inner or outer
portion.
[0033] If desired, additional materials can be incorporated into
the ribbed structure. Examples of additional materials that can be
incorporated into the RS include be filled with materials other
than air, such as resins, foams, insulating materials, or NVH
(noise, vibration, or harshness) damping materials, and/or the
like.
[0034] The RS need not be uniform in the structural member. In one
aspect of the embodiment, the type of ribs in the RS can vary from
location to location. Further, multiples types of RSs can be
combined in the at least one layer of the intermediate portion. In
another aspect of the invention, the periodicity and/or thickness
of the ribs can be changed in different areas of the at least one
layer of the intermediate portion. In another aspect of the
invention, the strength and other physical properties of the ribs
can change from one location to another.
[0035] The ribs of the RS can be made of any suitable material
exhibiting the desired structural properties. Suitable materials
include any material known in the art to provide such a function,
including materials having individual cells like beads, corrugated
materials, thermoplastic molded materials, honeycomb materials, and
foams such as flexible expanded plastic foams, polymer foams, metal
components, flexible metal (i.e., aluminum) foams, or any
combination of these materials. See, for example, U.S. Pat. Nos.
5,344,038, 4,573,707, 5,562,981, 4,128,963, 4,968,545, and
5,894,045, the disclosures of which are incorporated herein by
reference.
[0036] A preferred intermediate portion 6 may be formed using
honeycomb materials (also known as honeycomb cores). These
materials usually comprise a thin sheet (or sheets) of material,
such as paper or aluminum foil, which is formed into a variety of
random or geometric cellular configurations. See U.S. Pat. No.
5,876,654, the disclosure of which is incorporated herein by
reference. Honeycomb cores, which have a geometric cellular
configuration, are known to have structural properties or
characteristics that are superior to most foam or solid cores with
a comparable density. Honeycomb cores can be made of various shapes
and types of materials such as aluminum, aramid materials such as
Korex.RTM., nylon materials such as Nomex.RTM., plastic, reinforced
phenols, carbons, and fiberglass, or a combination thereof.
Preferably, honeycombs made of Nomex.RTM. are employed as the
material for intermediate portion 6.
[0037] The material and configuration (width, length, and geometric
shape) of the cells can be optimized to provide the desired support
and/or stabilization to the inner and outer portions. For example,
the cell size can range from about 1/8 to about {fraction (3/4)}
inches, and is preferably about {fraction (3/16)} inches.
[0038] The cells of the honeycomb cores can be filled with
materials other than air, such as resins, foams, insulating
materials, or NVH (noise, vibration, or harshness) damping
materials, and/or the like. The type of material used, the
thickness, the cell configuration, and "fill-in" material for
intermediate portion 6 can vary along the length of structural
member 2.
[0039] 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, intermediate, and/or outer portions
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.
[0040] The structural member of the 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
structural member 2.
[0041] 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.
[0042] In one aspect of the invention, the structural members of
the present invention have the contoured shapes illustrated in FIG.
16. The 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. 16, 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. 17, 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.
[0043] In another aspect of the invention, the shape of the
structural member has a shape other than substantially circular in
cross-section. 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 like the brackets
mentioned above.
[0044] 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 can be
"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.
[0045] In another aspect of the invention, the shape of the
structural member can be "shaped" or modified to be not
substantially straight (or bent). In one aspect of the invention,
the structural member (or a portion thereof) can made with a
substantially non-straight shape. For example, as described in more
detail below, the structural member of the invention could be made
using a substantially non-straight mandrel to obtain the
substantially non-straight shape as illustrated in FIG. 18. In
another example, the structural member could be made by roll
wrapping the inner, intermediate and outer portions on a hollow,
flexible, straight shaped mandrel, and then bending to a desired
shape and curing to obtain the shape illustrated in FIG. 18. The
structural members of the invention can have a non-circular
cross-section (triangular, rectangular, hexagonal, elliptical, and
the like) as well as a substantially non-straight shape, as
depicted in FIG. 19.
[0046] In another aspect of the invention, the structural member
(or a portion thereof) can be made with a substantially straight
shape, and then bent to have a substantially non-straight shape.
For example, the structural member could be made by roll wrapping
the inner, intermediate and outer portion on a hollow
straight-shaped mandrel with a bladder, subjecting the assembly
into a freeze, then removing the mandrel, and finally placing the
intermediate structure in a mold and curing it in the mold. The
structural member can be modified or bent using any number of
methods as described in more detail below.
[0047] Additional structural components are added to modify the
structural member for any desired end use. In one aspect of the
invention, additional structural components are added to make it
suitable as a part or component in any type of vehicle, whether
motorized or not, and whether traveling on land, water, or in the
air. For example, the structural member can be modified by adding
those structural components necessary to have the structural member
serve as a bumper, cross car beam, frame rails, etc. . . .
[0048] Structural member 2 can be made crushable by any manner in
the art. In one aspect of the invention, the structural members are
made crushable by including at least one crushing initiator (or
initiator) adjacent to (or in) portion 4, portion 6, and/or portion
8. For example, as depicted in FIG. 12, the at least one initiator
14 can be incorporated in outer portion 8. However, the at least
one initiator can be incorporated in inner portion 4, intermediate
portion 6, and/or outer portion 8, as well as between these
portions.
[0049] The initiator controls the location where, when an external
load is applied, structural member 2 begins to deform. Often, the
structural member resists impacts along its longitudinal axis. By
including an initiator, the structural member of the present
invention absorbs the energy of the load by undergoing a localized
crush where the initiator is located, in modes such as transverse
shearing, lamina bending, or local buckling like monocell buckling,
face wrinkling, or core-shear instability. Thus, the initiator
leads to a localized crush of the member so the structural member
does not fail at other places. By incorporating at initiator, the
preferred site of collapse of the structural member can be selected
before the expected load is applied.
[0050] Any suitable initiator known in the art can be employed in
the present invention, including those described in U.S. Pat. Nos.
4,742,889, 5,732,801, 5,895,699, and 5,914,163, the disclosures of
which are incorporated herein by reference. The initiator can be
placed at any location of structural member 2 depending on the
desired characteristics including the crushing strength and
crushing length. Preferably, the initiator is not located at the
ends of structural member 2. More preferably, the initiator is
placed at least about {fraction (1/2)} inch to about 2 inches away
from any end of structural member 2.
[0051] Multiple initiators can be placed along separate portions of
member 2 to deform (and therefore crush) several locations.
Multiple initiators can also be placed proximate one another at a
single portion of member 2 to deform that selected location. The
number of initiators can vary, depending on the desired crushing
strength and desired crushing length.
[0052] The initiator(s) can be of various shapes, sizes, and
configurations, but should be substantially similar to the
configuration of portion 4, intermediate portion 6, and/or portion
8. The width of the initiator can vary depending on the expected
load, the desired crushing strength, and the desired crush length.
For example, the width can range from about {fraction (1/16)}
inches to about 1 inch, and is preferably about {fraction (1/2)}
inches. The shape of the initiator can also vary depending on the
expected load, the desired crushing strength, and the desired crush
length. Generally, the shape is similar to that portion of
structural member 2 into which it is incorporated. Thus, the shape
can vary from circular, to rectangular or triangular, to any
polygonal shape.
[0053] When multiple initiators are employed, they can be located
in any desired location. In one aspect of the invention, the
initiators can be either staggered or inline. The initiators can be
inline, meaning that multiple initiators are aligned along the
length or diameter of the structural member. The initiators can
also be semi-staggered or fully staggered. In a semi-staggered
position, the initiators are only partially aligned along a length
or diameter of the structural member, e.g., they have overlapping
positions (as illustrated in FIG. 13). In a fully staggered
position, the initiators are not aligned along the length or
diameter of the structural member, e.g., they have no overlapping
positions (as illustrated in FIG. 14).
[0054] Any suitable material can be used for the initiator(s) of
the present invention. Suitable materials used for the initiator
can be any material which causes, as explained below, the
respective inner and/or outer portion to deform and do not adhere
to the materials used in the inner, intermediate, and/or outer
portion. Examples of suitable materials include as teflons, rubber
bands, brominated teflon coated glass fabric (brominated films),
release films, rubber films, polytetrafluoroethylene (PTFE) tape,
backing papers, or a combination thereof. In one aspect of the
invention, brominated ("bromo") films are preferably employed as
the material for the initiator in the present invention.
[0055] Bromo films are brominated PTFE coated fiber glass fabric
films. Bromo films are usually an impermeable layer that does not
bond to the composite material during the curing process (as
described below). There are two types of bromo films that can be
employed as the initiator material: porous and non-porous.
Preferably, a non-porous bromo film is employed as the initiator
material, ensuring that there is an unbonded area in any desired
location that will cause the failure in that particular location.
Numerous bromo films are commercially available, including "Release
Ease 234TFP" sold by Air Tech Advanced Materials Group.
[0056] It is believed that the initiator works because of the
absence of a continuous layer in the inner, intermediate, and/or
outer portion. Thus, the initiator could also be a gap or
discontinuity (such as a stress riser) in the layer(s) of the
inner, intermediate, and/or outer portion. The discontinuity could
be a singular discontinuity such as a fold or irregularity, or
plural discontinuities such as a row or column of cut-outs having
any desired shape and size. For example, as illustrated in FIG. 15,
a row of cut-outs can be located in a layer of the inner and/or
outer portion, as well as the intermediate portion, so that when
assembled, structural member 2 contains at least one initiator 14.
In addition, when the impact load is an axial load, the initiator
could be any material (or lack thereof) which operates as a local
stress riser.
[0057] The present invention can be made by any suitable process
yielding the structure of structural member 2. 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.
[0058] 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, with a
shape generally corresponding to the desired shape (core region 10)
of structural member 2. Any suitable mandrel, 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. The substrate or mandrel must have sufficient strength,
desired shape, and be able to withstand the processing conditions
for making the structural member, e.g., ductile enough to be able
to be manufactured (or bent after manufacture) to the desired
shape. Suitable mandrels include those made of metals like steel
and aluminum, polycarbonate, thermoset or thermoplastic rubber
materials, thermoplastics (including flexible thermoplastics), or
RRMM (including flexible RRMM) materials. The mandrels may be solid
or hollow.
[0059] 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 herein or as
known in the art.
[0060] 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) of the metal-containing material or 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. When a continuous metal sheet is used, there is no
need for such a stacking operation. After forming inner portion 4,
the material comprising intermediate portion 6 is placed,
preferably by wrapping or rolling, on inner portion 4 by hand or
mechanical apparatus. The roll wrapping process is then resumed 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. Additional
layers or materials-such as a coating-can be added over outer
portion 8, if desired, in a similar manner or as known in the
art.
[0061] 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.
Of course, when a continuous metal sheet is rolled, no butt joint
occurs.
[0062] 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.
[0063] If desired, a bonding agent can be placed between successive
layers of portions 4, 6, 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.
[0064] Where portions 4, 6, and 8 are successively layed up in an
uncured (e.g., B-stage state), the structure has outer portion 8
overlying intermediate portion 6, which overlies inner portion 4,
which overlies the mandrel. If necessary to better bond and connect
inner portion 4, intermediate portion 6, 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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 corners, 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.
[0069] 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.
[0070] 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.
[0071] Second, the inner portion can have a substantially polygonal
shape (i.e, square) and the outer portion a substantially circular
shape. In this aspect of the invention as depicted in FIG. 9, the
process for making a square-shaped structural member is followed as
described above. To change the shape of the outer portion, the
pressure distributors which 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] At least one initiator 14 may be included in the present
invention by any suitable method, including those known in the art.
If only one layer is employed for portion 4, intermediate portion
6, and/or portion 8, the initiator can be created under, in, or
over that single layer. When more than one layer is employed for
such portions, such an initiator(s) can, additionally or
alternatively, be included between the layers making up the
respective portion.
[0079] For example, when the initiator is a gap or discontinuity in
portion 4, intermediate portion 6, and/or portion 8, the desired
section of that portion can be removed or altered. Any gap or
discontinuity is preferably, although not necessarily, formed in
the material prior to the roll wrapping operation. The initiator
can consist of rows or columns of cutouts of any desired shape and
size, as exemplified in FIG. 15, in the respective material which
have been removed by any suitable process known in the art, such as
stamping. The desired configuration for the initiator is selected,
the desired location(s) for deformation of the structural member
are determined, and the initiator(s) is then placed by creating a
gap or discontinuity in the respective layer(s) of portion 4,
portion 6, and/or portion 8 either before or after the rolling
operation.
[0080] As another example, when the initiator is similar to that
illustrated in FIG. 12, the desired width of the initiator material
can placed on the selected locations(s) of portion 4, intermediate
portion 6, and/or portion 8. The initiator material could be placed
by rolling or wrapping the initiator material under or on the
respective inner, intermediate, and/or outer portion.
Alternatively, the initiator material could be placed in or on the
sheet(s) prior to the rolling or wrapping process, e.g., by
manufacturing the sheet(s) with the initiator formed therein. The
desired material and configuration for the initiator is selected,
the desired location(s) for deformation of the structural member
are determined, and the initiator(s) is then placed under, over, or
within the layer(s) of portion 4, 6, and/or 8 either before or
after the rolling operation.
[0081] 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 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 such shapes and configurations are shown in FIG. 10.
[0082] In one aspect of the invention, the structural members are
manufactured with a substantially non-straight or bent shape as
illustrated in FIGS. 18 and 19. In this aspect of the invention, a
procedure similar to the process depicted in FIG. 20A is employed.
When the inner, intermediate, and outer portions are formed on the
mandrel, such portions (and the structural member) will have a
similar shape. The structural member is then cured and molded. If
necessary, non-solid mandrels 120 (such as inflatable or mandrels
having separable parts) can be used (or substituted for a solid
mandrel) in order to help remove the mandrel after the structural
member has been made. See, for example, FIG. 20 illustrating that
the mandrel can be removed before or after the molding stage.
[0083] In another aspect of the invention, the structural member
(or a portion thereof) can be formed in an alternative manner. In
this aspect of this invention, the curing and molding stages can be
combined in a single step as illustrated in FIGS. 21 and 21A, where
FIGS. 21 and 21A depict a different type of curing/molding
procedure. Otherwise, the process is substantially the same as that
described above.
[0084] In another aspect of the invention, the structural member
(or a portion thereof) can be formed in an alternative manner. In
this aspect of the invention, and as illustrated in FIG. 22, a part
of the structural member (such as the inner portion) or a
length-wise section of the structural member is made substantially
straight and then is modified (bent) into a substantially
non-straight shape. Thus, any number of bent shapes and complex
configurations can be obtained for the inner portion. In this
aspect of the invention, a hollow inner portion 4 is made using any
of the methods known in the art, such as filament winding, roll
wrapping, extrusion, molding, pultrusion, or braiding, and then it
can be modified (or bent) into a non-straight shape using vacuum
forming, thermoforming, hydroforming, bladder molding, etc. . . .
The shape of the inner portion can be any desired shaped including
triangular, rectangular, hexagon, polygon, elliptical, etc. . .
.
[0085] Next, the resulting structure is heated and placed into a
mold or a cast. In this step, an external mold with the desired
shape--the inner shape of the mold is the same shape as the outer
surface of the structural member) is fit over the outside of the
intermediate structure (or vice versa). The external mold can be
made of any material as known in the art that is capable of
withstanding the operating pressures and temperatures used in the
molding process, such as steel, aluminum, or a composite
material.
[0086] After placed in the mold, the shape of the structural member
is then modified to match the size of the mold. This step can be
performed using any known forming technique known in the art, such
as hydroforming, bladder molding, vacuum forming, or thermoforming.
See, for example, U.S. Pat. Nos. 6,055,715, 6,183,013, and
6,216,509, the disclosures of which are incorporated herein by
reference. In one aspect of the invention, an internal pressure
(within inner portion 4) is applied in any suitable manner. In one
aspect of the invention, the internal pressure is applied using a
fluid such as a gas or liquid like as water. The inner surface of
the inner portion 4 can be protected during this step using
pressurized tubing or a barrier film on the inner surface of inner
portion 4.
[0087] When applied correctly, this internal pressure modifies the
shape of the structural member to conform to the mold. The time and
amount of pressure is selected so that the structural properties
(other than the shape) of the member are not damaged, as well as
the desired dimensions are retained.
[0088] Next, optional intermediate portion and the outer portion
are applied using any of the above-mentioned methods. When used,
the materials used for the intermediate portion must be selected to
permit bending--both stretching and contracting--of the
intermediate portion. In this aspect of the invention, flexible
foams, preformed honeycomb, or any preformable materials can be
employed as the material for the intermediate portion. If a mandrel
is used in this part of the process, the preformed intermediate
portion can be cut open and then removed.
[0089] In yet another aspect of the invention, the inner and
intermediate portion can be formed and then placed in the mold.
After the shape of the inner and intermediate portions are modified
as described immediately above, the outer portion is then formed on
the intermediate portion, as depicted in FIG. 23.
[0090] Once the shape of the structural member has been modified,
the mold is removed from the structural member. The member is then
further processed as described above. In one aspect of the
invention, additional structural components 130 such as brackets,
fasteners, couplers, etc. can be added before structural member is
cured that means they are in-mold.
[0091] In one aspect of the invention, such additional structural
components could be attached to the structural members using any
suitable technique. Suitable techniques include any known
attachment technique, such as structural adhesive bonding, u.v.
light cure adhesive bonding, film adhesive bonding, or other
adhesive bonding technique. As well, new attachment techniques such
as hot plate welding, ultrasonic, vibration, TP welding, injection
molding, etc. could be used to attach the structural
components.
[0092] As described above, any structural components known in the
art--such as brackets, fasteners, couplers etc.--an be added to the
structural member. In this aspect of the invention, the surfaces to
be joined are cleaned with suitable solvent, followed by a surface
abrasion for mechanical locking purposes. If desired, a suitable
adhesive primer may be used. A suitable adhesive is then selected,
weighed per the manufacturer's recommendation, mixed, and then
applied on the surface to be joined. The parts are then assembled
and held together with pressure using an appropriate fixture until
the adhesive is substantially or fully cured.
[0093] Alternatively (or additionally), the structural members can
be threaded on the inside and the parts can be threaded with a
matching geometry. The parts and the structural member could then
be threaded together, with the threads providing mechanical
locking. In another aspect of the invention, the structural members
are prepared with a hexagonal shape inside, and the parts are
prepared with a matching hexagonal outer portion. The parts are
then bonded to the structural member using an appropriate adhesive.
The joined sections are then overwrapped with a "B" stage
unidirectional material (such as a prepreg) in an oriented manner
to provide additional torque resistance.
[0094] Generally, the method of bonding attachments depends on type
of material (or substrate) to be bonded. If two similar
materials--such as thermoplastic-based substrates--are to be
bonded, other methods such as ultrasonic welding or hot plate
welding can be utilized. If two substrates with dissimilar
materials--such as metal to composite or to plastic--then a
structural adhesive is utilized. As an example of this aspect of
the invention, FIGS. 24 depicts a process for incorporating
brackets in a composite-based bent structural member.
[0095] The structural member of the present invention has numerous
uses such as a bumper, cross car beam, tie rod, 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, 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.
[0096] The following non-limiting examples illustrate the present
invention.
EXAMPLE 1 (HYPOTHETICAL)
[0097] A cylindrical bent structural member with a circular
cross-section can be made according to following process. A thin
coat of a release material (Frekote 700NC or Axel EM606SL/SP) will
be applied to a 3 inch diameter aluminum mandrel with a length of
52 inches.
[0098] Two metal (aluminum) sheets with preapplied adhesive and a
thickness of about 0.001 inch will be pattern cut with a
measurement of about 38 inches in width and about 48 inches in
length. In both sheets, about 0.25 inch diameter holes, about 1
inch apart, will be punched about 2 inches away from the "side" end
of the metal sheet. The holes will be punched, leaving the first 10
inches from the leading end of the sheet (that end first wrapped
onto the mandrel) without any holes and the remaining 28 inches
with holes.
[0099] One of the metal sheets will be then roll wrapped by hand
onto the aluminum mandrel starting with the metal portion against
the mandrel, e.g., so the adhesive material will be on the top.
After rolling, the metal sheet of the inner portion will be four
layers "thick" on the mandrel: the first layer containing those
portions of the sheet with no punched holes and the least three
layers having the punched holes.
[0100] Next, a honeycomb Hexcell Nomex.RTM. core with hexagonal
shaped cells and a thickness of about 0.15 inches will be measured
and cut to dimensions of about 10 inches by about 48 inches. About
0.25 inch diameter holes, about 1 inch apart, will be punched about
2 inches away from the "side" end of the honeycomb. This honeycomb
core will be then roll wrapped by hand on the first metal sheet,
with the honeycomb core adjacent to the adhesive of the last layer
of the first metal sheet.
[0101] Next, the resulting intermediate structure will be placed in
a freezer overnight. After cooling the structure, the mandrel will
be removed and a bladder molding balloon will be introduced. The
structure will be brought to room temperature and then placed in a
bent mold. Pressure will be applied to the inside of the structure
by inflating the balloon. The structure will then be subject to a
curing process at about 250 degrees Fahrenheit for about 120
minutes during which the balloon will apply pressure to the
intermediate structure from the inside and the mold will help to
form the outer shape. After this curing process, the bladder will
be deflated and the structural member will be removed from the
mold.
EXAMPLE 2 (HYPOTHETICAL)
[0102] A cylindrical bent structural member with a square-shaped
cross section can be made according to following process. A thin
coat of a release material (Frekote 700NC or Axel EM606SL/SP) will
be applied to a cylindrical aluminum mandrel with a 3.0 inch square
outer diameter and a length of 72 inches. A bladder will be rolled
over the mandrel.
[0103] One layer of Dacron/Teflon woven fabric will be cut about
11.6 inches in width and 64 inches in length. The individual sheet
will be roll wrapped over the mandrel.
[0104] Four pairs of B-stage prepreg laminate sheets (8 individual
sheets) containing anisotropic Kevlar fibers in an epoxy-based
resin will be cut with measurements of about 11.6 to 13.4 inches in
width and about 64 inches in length. The individual laminate sheets
will then be overlaid so the fibers in successive sheets are
symmetric and balanced at angles of .+-.15 degrees. The air between
the stacked sheets will be removed by using a roller or other
suitable device. Two pairs of the stacked prepreg sheets will be
then roll wrapped by hand onto the aluminum mandrel.
[0105] Then, {fraction (1/2)} inch wide strips of bromo film will
be measured and cut to a length similar to the outside diameter of
the stacked sheets on the mandrel, e.g., 121/2 inches in length.
The strips will be then roll wrapped over the prepreg sheets on the
mandrel. The strips will be located such, that when the structural
member will be cut as described below, the strips will be about 2
inches away from any desired end of the structural member.
[0106] Next, a honeycomb Hexcell Nomex.RTM. core with hexagonal
shaped cells and a thickness of about 0.2 inches will be measured
and cut to dimensions of about 13 inches by about 64 inches. This
honeycomb core will be then roll wrapped by hand on the first set
of stacked prepreg sheets and strips of bromo film.
[0107] Additional {fraction (1/2)} inch wide strips of bromo film
will be measured and cut to a length similar to the outside
diameter of the honeycomb core. The strips will be then roll
wrapped over the honeycomb core to be aligned with the strips under
the core. The other two pairs of the stacked prepreg sheets will be
then roll wrapped onto the honeycomb core and the strips of bromo
film.
[0108] Next, the mandrel will be removed from the resulting
intermediate by inflating bladder with a little air. The structure
will then be placed in a bent mold with matching square shape mold.
Pressure will be applied to the inside of the structure by
inflating the bladder. The structure will then be subjected to a
curing process at about 250 degrees Fahrenheit for about 120
minutes during which the bladder will apply pressure to the
intermediate structure from the inside and the mold will help to
form outer shape. After this curing process, the bladder will be
deflated and the structural member will be removed from the
mold.
EXAMPLE 3 (HYPOTHETICAL)
[0109] A cylindrical bent structural member with a circular
cross-section will be made according to following process. A thin
coat of a release material (Frekote 700NC or Axel EM606SL/SP) can
be applied to a 0.729 inch diameter circular steel mandrel with a
length of 64 inches.
[0110] A pair of B-stage prepreg laminate sheets (2 individual
sheets) containing anisotropic carbon fibers in an epoxy-based
resin can be cut with measurements of about 2.31 to 2.34 inches in
width and about 60 inches in length. The individual laminate sheets
can be overlaid so the fibers in successive sheets were symmetric
and balanced at angles of .+-.80 degrees. The air between the
stacked sheets will be removed by using a roller.
[0111] 21 individual sheets of B-stage prepreg laminate sheets
containing anisotropic carbon fibers in an epoxy-based resin will
be cut with measurements of about 2.37 to 2.99 inches in width and
about 60 inches in length. The individual laminate sheets will be
overlaid so the fibers in successive sheets are symmetric and
balanced at angles of .+-.10 degrees. The air between the stacked
sheets will be removed by using a roller.
[0112] Another pair of B-stage prepreg laminate sheets (2
individual sheets) containing anisotropic carbon fibers in an
epoxy-based resin can be cut with measurements of about 3.02 to
3.05 inches in width and about 60 inches in length. The individual
laminate sheets will be overlaid so the fibers in successive sheets
will be symmetric and balanced at angles of .+-.80 degrees. The air
between the stacked sheets will be removed by using a roller.
[0113] Two layers of .+-.80, 21 layers of .+-.10, and another two
layers of .+-.80 will be stacked and air between the stacked layers
will be removed by using a roller. The stacked prepreg sheets will
be then roll wrapped by hand onto the mandrel.
[0114] Next, the resulting intermediate structure can be
shrink-wrapped. One layer of polyethylene-based shrink-wrap tape
can be roll wrapped by a shrink-wrapping machine using gauge number
150 on the resulting structure. Next, the resulting intermediate
structure will be placed in a freezer over night. After cooling the
structure, the mandrel will be removed and a bladder introduced.
The structure will be brought to room temperature and placed in a
bent mold. Pressure will be applied to the inside of the structure
by inflating the bladder. Alternatively, the structural member can
be pressurized using hydroforming. The structure will then be
subjected to a curing process at about 250 degrees Fahrenheit for
about 120 minutes during which the bladder will apply pressure to
the intermediate structure from the inside and the mold will help
form the outer shape. After this curing process, the bladder will
be deflated and the structural member removed from the mold.
[0115] 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.
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