U.S. patent number 9,993,993 [Application Number 15/220,352] was granted by the patent office on 2018-06-12 for joined fiber-reinforced composite material assembly with tunable anisotropic properties.
This patent grant is currently assigned to Carbitex, Inc.. The grantee listed for this patent is Carbitex, Inc.. Invention is credited to Keshava Bhamidipaty, Tyler Andre Kafentzis, Junus Ali Khan, Kevin Lynn Simmons.
United States Patent |
9,993,993 |
Simmons , et al. |
June 12, 2018 |
Joined fiber-reinforced composite material assembly with tunable
anisotropic properties
Abstract
An anisotropic composite material assembly comprising a first
layer with a tensile modulus different from its compressive modulus
and that exhibits variable modulus behavior. The first layer
elastically buckle under compressions. A second layer has a tensile
modulus substantially the same as its compressive modulus. The
first and second layers are joined together, and the assembly is
bendable in a first direction with an outer surface of the first
layer being in compression and the assembly has a first bending
stiffness during bending in the first direction. The assembly is
bendable in a second direction opposite the first direction with
the outer surface of the first layer being in tension, and the
assembly has a second bending stiffness greater than the first
bending stiffness during bending in the second direction.
Inventors: |
Simmons; Kevin Lynn (Kennewick,
WA), Khan; Junus Ali (Pasco, WA), Kafentzis; Tyler
Andre (Richland, WA), Bhamidipaty; Keshava (Richland,
WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Carbitex, Inc. |
Kennewick |
WA |
US |
|
|
Assignee: |
Carbitex, Inc. (Kennewick,
WA)
|
Family
ID: |
56787670 |
Appl.
No.: |
15/220,352 |
Filed: |
July 26, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170157893 A1 |
Jun 8, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62262335 |
Dec 2, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A43B
13/12 (20130101); B32B 27/12 (20130101); B32B
7/02 (20130101); B32B 15/00 (20130101); B32B
27/365 (20130101); A43B 13/026 (20130101); A43B
13/141 (20130101); B32B 5/024 (20130101); B32B
5/26 (20130101); B32B 2260/046 (20130101); B32B
2262/106 (20130101); B32B 2307/546 (20130101); B32B
2307/706 (20130101); B32B 2260/048 (20130101); B32B
2437/02 (20130101); B32B 2260/021 (20130101); B32B
2307/54 (20130101) |
Current International
Class: |
B32B
7/02 (20060101); A43B 13/14 (20060101); B32B
5/02 (20060101); A43B 13/12 (20060101) |
Field of
Search: |
;442/179,103,104 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2466792 |
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Jul 2010 |
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GB |
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TO2015A000061 |
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Jan 2018 |
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IT |
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2007046118 |
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Apr 2007 |
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WO |
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2014160506 |
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Oct 2014 |
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WO |
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2016120785 |
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Aug 2016 |
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WO |
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Other References
"Properties of Carbon Fiber--Clearwater Composites, LLC" webpage
http://www.clearwatercomposites.com/resources/Propertiesofcarbonfiber,
archived Dec. 20, 2014, accessed May 19, 2017. cited by examiner
.
International Searching Authority, International Search Report and
Written Opinion, PCT Application PCT/US2016/044123, dated Sep. 21,
2016, 17 pages. cited by applicant.
|
Primary Examiner: Ewald; Maria V
Assistant Examiner: Davis; Zachary M
Attorney, Agent or Firm: Perkins Coie LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION(S)
This non-provisional patent application claims the benefit of and
priority to U.S. Provisional Patent Application No. 62/262,335,
titled Composite Beam Construction with Tunable Anisotropic
Properties, filed Dec. 2, 2015, and which is incorporated herein in
its entirety by reference thereto.
Claims
We claim:
1. An anisotropic composite material assembly, comprising: a first
layer of flexible, fiber reinforced composite material with a
plurality of arranged fibers within a low modulus matrix material,
the first layer having a first rigidity, a first tensile modulus
and a first compressive modulus lower than the first tensile
modulus, such that the first layer of the assembly is configured to
elastically buckle under compression; a rigid second layer fixedly
joined to the first layer, the second layer having a second
rigidity, with the first rigidity being less than the second
rigidity; wherein the assembly is elastically bendable in a first
direction with an outer surface of the first layer being in
compression, the assembly has a first bending stiffness during
bending in the first direction; and wherein the assembly is
elastically bendable in a second direction opposite the first
direction with the outer surface of the first layer being in
tension, the assembly has a second bending stiffness greater than
the first bending stiffness during bending in the second direction
while exhibiting variable modulus behavior.
2. The anisotropic composite material assembly of claim 1 wherein
the plurality of arranged fibers of the first layer are impregnated
with the low modulus matrix.
3. The anisotropic composite material assembly of claim 1 wherein
the plurality of arranged fibers of the first layer are
encapsulated with the low modulus matrix.
4. The anisotropic composite material assembly of claim 1 wherein
the first layer is orthotropic.
5. The anisotropic composite material assembly of claim 1 wherein
the first layer comprises a shaped or perforated material.
6. The anisotropic composite material assembly of claim 1 wherein
the first layer has a first tensile modulus in the range of
approximately 3 ksi-5,000 ksi.
7. The anisotropic composite material assembly of claim 1 wherein
the first layer comprises a plurality of sheets joined
together.
8. The anisotropic composite material assembly of claim 1 wherein
second layer comprises a rigid composite material.
9. The anisotropic composite material assembly of claim 1 wherein
the second layer comprises a rigid non-fibrous material.
10. The anisotropic composite material assembly of claim 1 wherein
the second layer comprises a plurality of sheets joined
together.
11. The anisotropic composite material assembly of claim 1 with a
neutral orientation wherein the first and second layers are not
subjected to bending load, and the first and second layers are
planar layers in the neutral orientation.
12. The anisotropic composite material assembly of claim 1, with a
neutral orientation wherein the first and second layers are not
subjected to bending load, and the first and second layers are
curved or contoured.
13. The assembly of claim 12, wherein the assembly is configured to
have a plurality of flex ranges between a flat planar configuration
at approximately 0 degrees bend in the assembly to a fully bent
configuration with approximately a 50-56 degree bend in the
assembly, and wherein the assembly has a ratio of flexural moduli
in the range of approximately 1.25:1 to 20:1 between the flat
planar configuration and the fully bent configuration.
14. An anisotropic composite material assembly, comprising: a
non-rigid first layer having a first tensile modulus and a first
compressive modulus different than the first tensile modulus, the
first layer exhibiting variable modulus behavior, and where the
first layer of the assembly is configured to elastically buckle
under compression, wherein the first layer comprises a plurality of
arranged fibers substantially fully encapsulated in a matrix
material having a modulus of elasticity in the range of
approximately 5 to 5,000 psi, and a thin layer of thermoplastic
film having a film having a thickness in the range of approximately
0.0005-0.025 inches bonded to the fibers; a rigid second layer of a
substrate material having a second tensile modulus and a second
compressive modulus substantially the same as the second tensile
modulus; the first and second layers are joined together at an
intermediate interface area, with the thermoplastic film between
the arranged fibers and the substrate material; wherein the
assembly is elastically bendable in a first direction with an outer
surface of the first layer being in compression, the assembly has a
first bending stiffness during bending in the first direction; and
wherein the assembly is elastically bendable in a second direction
opposite the first direction with the outer surface of the first
layer being in tension, the assembly has a second bending stiffness
greater than the first bending stiffness during bending in the
second direction, and wherein the first layer of the assembly has a
ratio of change of flexural modulus based on bending in the second
and first directions in the range of approximately 1.264:1 to
7.609:1.
15. The anisotropic composite material assembly of claim 14,
further comprising a neutral bending plane located in the second
layer or at an interface between the first and second layers,
wherein the neutral bending plane is not located in the first layer
when the assembly bends in the first and second directions.
16. The anisotropic composite material assembly of claim 14 wherein
the second layer comprises a plate with the second compressive
modulus in the range of approximately 30 ksi 40,000 ksi.
17. The anisotropic composite material assembly of claim 14 wherein
the first layer comprises a woven fabric of fiber having an offset
angle.
18. The anisotropic composite material assembly of claim 14 wherein
the first layer comprises a fabric with a weave pattern comprising
a first fabric tensile modulus in one direction and a second fabric
tensile modulus different than the first fabric tensile modulus in
a direction transverse to the one direction and in the same
plane.
19. The anisotropic composite material assembly of claim 14,
further comprising a flex area and a neutral orientation in which
the first and second layers are not subjected to bending load, and
the first and second layers are curved at the flex area.
20. The anisotropic composite material assembly of claim 19 wherein
the first layer is in compression and the fibers are elastically
buckled when the assembly is in a flat, planar orientation.
21. The anisotropic composite material assembly of claim 14 wherein
the assembly is in a midsole assembly or insole of an article of
footwear.
22. An anisotropic composite material assembly, comprising: a
non-rigid first layer comprising at least one fiber-reinforced
composite material with fabric having first fibers interlaced with
second fibers at a selected angle relative to each other, and an
elastically deformable matrix encapsulating or impregnating the
fabric, wherein the matrix has a matrix modulus of elasticity in
the range of approximately 5 to 5,000 psi, wherein the first layer
has a first modulus of elasticity, and the first or second fibers
of the at least one fiber-reinforced composite material are
configured to bend and buckle under compressive loads on the first
layer; a rigid second layer joined to the first layer at an
intermediate interface area, the second layer comprising rigid
material having a second modulus of elasticity; a thin layer of
thermoplastic film substantially at the intermediate interface
area, the film having a thickness in the range of approximately
0.0005-0.025 inches and being bonded to the first and second
fibers, and bonded to the second layer; wherein the assembly is
elastically bendable about an axis in a first direction that puts
the first layer in tension and the second layer in compression, and
the assembly has a first bending stiffness when the assembly is
bent in the first direction; wherein the assembly is elastically
bendable about the axis in a second direction substantially
opposite the first direction, and bending in the second direction
puts the second layer in tension and the first layer in compression
causing the first or second fibers to elastically buckle, and the
assembly has a second bending stiffness less than the first bending
stiffness when the assembly is bent in the second direction; and
wherein the assembly has a neutral bending plane located in the
second layer or at the intermediate interface area between the
first and second layers, wherein the neutral bending plane is not
located in the first layer when the assembly bends in the first and
second directions.
23. The anisotropic composite material assembly of claim 22 with a
neutral orientation wherein the first and second layers are not
subjected to bending load, and the first and second layers are
flat, planar layers in the neutral orientation.
24. An anisotropic composite material assembly, comprising: a
non-rigid first layer comprising a non-rigid first fiber-reinforced
composite material with fibers impregnated with matrix, wherein the
first layer has a first tensile modulus and a first compressive
modulus different than the first tensile modulus, wherein the
fiber-reinforced composite material being configured to bend and
elastically buckle under compression loads in the first layer; a
rigid second layer comprised of a fiber-reinforced composite
material joined to the first layer and having a second tensile
modulus greater than the first tensile modulus, and the second
layer has a second compressive modulus substantially the same as
the second tensile modulus; wherein the assembly bends in a first
direction that puts the first layer in tension and the second layer
in compression, and the assembly has a first bending stiffness when
the assembly is bent in the first direction; and wherein the
assembly bends in a second direction substantially opposite the
first direction that puts the second layer in tension and the first
layer in compression causing the first layer to elastically buckle,
and wherein the assembly has a second bending stiffness less than
the first bending stiffness when the assembly is bent in the second
direction.
Description
TECHNICAL FIELD
This application relates in general to anisotropic materials, and,
in particular, to composite beam construction with tunable
anisotropic properties, including assemblies incorporating the
composite beam construction.
BACKGROUND
In general, materials are isotropic or anisotropic. Isotropic
materials have identical properties in all directions. Conversely,
properties of anisotropic materials are directionally and
geometrically dependent.
Conventionally, in applications that require the use of materials
that permit bending, materials such as metal, polymers, or
composite can be used to form flexural beams. The modulus of the
materials used in the beams and their geometry influence the
stiffness. Depending on the material used to construct the beam,
the beam can have isotropic or anisotropic properties.
Nevertheless, beams constructed with such materials have an
inherent inability to exhibit a low bending resistance in one
direction and a high bending resistance in the other. Furthermore,
these materials exhibit a linear relationship between stress and
strain.
Many products, such as consumer products, including footwear and
apparel, medical devices, medical appliances, manufacturing
products, and many other products, incorporate materials to provide
a selected degree of stiffness while still allowing for some
flexibility for bending during use. However, oftentimes, desired
characteristics within a shoe or other similar products can be at
odds with other desired characteristics. For example, footwear
often incorporates materials that allow the sole assembly to bend
and flex with a wearer's foot during use, while also providing a
desired level of protection and structural stability to the foot.
For example, a sole assembly construction that provides enhanced
flexibility is often provided at the sacrifice of structural
stiffness and or stability. Conversely, the use of materials to
provide enhanced structural stiffness and stability are often at
the sacrifice of flexibility.
In materials with a linear relationship between stress and strain,
stiffness is constant. However, in many applications, materials
that increase stiffness as a function of strain are desirable. For
example, in some products such as footwear, it is desirable to
allow the footwear to bend in the toe region to allow the wearer's
toes to bend through a normal range of motion. It is also
desirable, however, for the footwear to provide a stiffness that
prevents the toe region from bending past the normal range of
motion resulting in a condition of increased strain, thereby
avoiding hyperextension of the wearer's toes (i.e., turf toe).
Similarly, it is desirable to provide a brace or other medical
appliance that allows for bending or articulation of a portion of a
wearer's body through a normal or selected range of motion. It is
also desirable, however, to provide a stiffness that prevents
articulation of the body portion beyond the normal or selected
range of motion, which would create a condition of increased
strain. The present technology can achieve this desirable
configuration that increases stiffness as a function of strain.
Linear stiffness behavior and tradeoffs between competing
performance and operating characteristics is often encountered in
the manufacturer and/or use of a wide variety of products.
Accordingly, there is a need for a material suitable for
applications requiring variable modulus material (i.e. anisotropic
flexural material or strain stiffening material).
SUMMARY
An embodiment of the present technology provides a joined,
fiber-reinforced composite material assembly with tunable
anisotropic properties. The assembly of an embodiment is configured
to exhibit a low resistance to bending in one direction and a high
resistance to bending in the other direction. At least one
embodiment provides an assembly usable in footwear, athletic
equipment and/or other products.
An embodiment of the present technology provides an anisotropic
composite material assembly comprising a first layer having a first
tensile modulus and a first compressive modulus lower than the
first tensile modulus, such that the first layer of the assembly is
configured to elastically buckle under compression. A rigid second
layer is fixedly joined to the first layer. The assembly is
elastically bendable in a first direction with an outer surface of
the first layer being in compression, and the assembly has a first
bending stiffness during bending in the first direction. The
assembly is elastically bendable in a second direction opposite the
first direction with the outer surface of the first layer being in
tension. The assembly has a second bending stiffness greater than
the first bending stiffness during bending in the second
direction.
Another embodiment of the present technology provides an
anisotropic composite material comprising a first layer having a
first tensile modulus and a first compressive modulus less than the
first tensile modulus. The first layer of the assembly is
configured to elastically buckle under compression. A second layer
is joined to the first layer. The second layer has a second tensile
modulus and a second compressive modulus substantially the same as
the second tensile modulus. The assembly is bendable in a first
direction with an outer surface of the first layer being in
compression, wherein the assembly has a first bending resistance
during bending in the first direction. The assembly is bendable in
a second direction opposite the first direction with the outer
surface of the first layer being in tension, and the assembly has a
second bending resistance greater than the first bending resistance
during bending in the second direction.
Another embodiment provides an anisotropic composite material
assembly. The assembly has a first layer comprising at least one
fiber-reinforced composite material with fabric having first fibers
interlaced with second fibers at a selected angle relative to each
other. An elastically deformable matrix encapsulates the fabric.
The first layer has a first modulus of elasticity in tension (i.e.,
first tensile modulus), and first or second fibers of the
fiber-reinforced composite material are configured to elastically
bend and buckle under compression loads on the first layer. A
second layer is joined to the first layer at an intermediate
interface area. The second layer comprises a rigid material having
a second modulus of elasticity in tension (i.e., second tensile
modulus) greater than or equal to the first tensile modulus. In
another embodiment, the second tensile modulus can be less than the
first tensile modulus. The assembly is bendable about an axis in a
first direction that puts the first layer in tension and the second
layer in compression. The assembly has a first bending stiffness
when the assembly is bent in the first direction. The assembly is
bendable about the axis in a second direction substantially
opposite the first direction, and bending in the second direction
puts the second layer in tension and the first layer in compression
causing the first or second fibers to elastically buckle. The
assembly has a second bending stiffness less than the first bending
stiffness when the assembly is bent in the second direction.
Another embodiment provides an anisotropic composite material
assembly having a first layer with a fiber-reinforced composite
material with fabric, and an elastically deformable matrix
encapsulating the fabric. The first layer has a first tensile
modulus, and the fiber-reinforced composite material is configured
to elastically bend and buckle under compression loads in the first
layer. A second layer is joined to the first layer and has a second
tensile modulus less than or equal to the first tensile modulus.
The second tensile modulus can be greater than the first tensile
modulus. The assembly bends in a first direction that puts the
first layer in tension and the second layer in compression, and the
assembly has a first bending stiffness when the assembly is bent in
the first direction. The assembly bends in a second direction
substantially opposite the first direction that puts the second
layer in tension and the first layer in compression causing the
first layer to buckle. The assembly has a second bending stiffness
less than the first bending stiffness when the assembly is bent in
the second direction.
Another embodiment provides an anisotropic composite material
assembly with a first layer having a first fiber-reinforced
composite material with fibers impregnated with matrix, wherein the
first layer has a first tensile modulus and a first compressive
modulus less than the first tensile modulus. The fiber-reinforced
composite material is configured to bend and elastically buckle
under compression loads in the first layer. A second layer
comprises a second fiber-reinforced composite material joined to
the first layer. The second layer has a second tensile modulus
greater than or equal to the first tensile modulus, and the second
layer has a second compressive modulus substantially the same as
the second tensile modulus. The second tensile modulus can be less
than the first tensile modulus. The assembly bends in a first
direction that puts the first layer in tension and the second layer
in compression, and the assembly has a first bending stiffness when
the assembly is bent in the first direction. The assembly bends in
a second direction substantially opposite the first direction that
puts the second layer in tension and the first layer in compression
causing the first layer to elastically buckle. The assembly has a
second bending stiffness less than the first bending stiffness when
the assembly is bent in the second direction.
Still other embodiments of the present invention will become
readily apparent to those skilled in the art from the following
detailed description, wherein is described embodiments of the
invention by way of illustrating the best mode contemplated for
carrying out the invention. As will be realized, the invention is
capable of other and different embodiments and its several details
are capable of modifications in various obvious respects, all
without departing from the spirit and the scope of the present
invention. Accordingly, the drawings and detailed description are
to be regarded as illustrative in nature and not as
restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the technology introduced herein may be better
understood by referring to the following Detailed Description in
conjunction with the accompanying drawings, in which like reference
numerals indicate identical or functionally similar elements.
FIG. 1A is an isometric view of a fiber-reinforced composite
material assembly with tunable anisotropic properties shown in a
planar, un-flexed configuration in accordance with an embodiment of
the present technology.
FIG. 1B is a schematic side elevation view of the assembly of FIG.
1A shown in phantom lines in an upward deflection configuration and
downward deflection configuration.
FIG. 2 is a schematic illustration showing, by way of example, a
three-point bend of a simple beam made of the assembly of FIG. 1A
positioned in a first orientation.
FIG. 3 is a schematic illustration showing, by way of example, a
three-point bend of the simple beam of FIG. 2, wherein the assembly
is in an upside down configuration with the bend in the opposite
direction of FIG. 2.
FIG. 4 is an enlarged cross sectional view taken substantially
along line 4-4 of FIG. 1A showing the top and bottom layers of the
assembly in accordance with an embodiment of the present
technology.
FIGS. 5-8 are graphs showing, by way of example, the differences
between flexural moduli in exemplary testing configurations.
FIG. 9 is a graph showing, by way of example, the flexural moduli
of an assembly in tensions and compression.
FIG. 10 schematic illustration showing, by way of example,
controlled buckling in a non-rigid carbon fiber material under
compression.
FIGS. 11A and 11B are illustrations showing, by way of example,
changes in fiber orientation when composite fiber material in the
assembly of FIG. 1A is strained along the longitudinal axis of a
segment of the material in accordance with an embodiment of the
present technology.
FIG. 12 is a schematic side view of an article of footwear with a
sole assembly that includes a laminate plate made of the assembly
of FIG. 1A.
FIG. 13 is a schematic cross-section of the sole assembly of FIG.
12 in accordance with one embodiment.
FIG. 14 is a schematic isometric view of a shoe insole made with a
joined, fiber-reinforced composite material assembly with tunable
anisotropic properties in accordance with an embodiment.
FIG. 15 is a schematic side view of the insole of FIG. 14
supporting a wearer's foot.
FIG. 16 is a graph showing the relationship of the flexural modulus
as a function of shoe torque and angle of curvature.
FIG. 17 is a cross-sectional view showing the construction of the
shoe insert of FIG. 16.
FIG. 18 is a diagram showing the layered construction of the
non-rigid flexible carbon fiber composite.
FIG. 19 is a diagram showing the layered construction of a
composite laminate.
FIG. 20 is a diagram showing, by way of example, column bending in
a non-rigid carbon fiber material.
FIG. 21 is a diagram showing the layered construction of a laminate
stack.
FIG. 22 is a diagram showing the change in length of each layer in
the laminate stack of FIG. 21 as the radius changes from an
original natural orientation.
FIG. 23 is a diagram showing the layered construction of the carbon
fiber joined plate.
FIG. 24 is a diagram showing a heat forming tool for use with the
carbon fiber joined plate of FIG. 23.
FIG. 25 is a graph showing, by way of example, the differences
between flexural moduli in exemplary testing configurations.
FIGS. 26A-B are illustrations showing, by way of examples,
controlled curvature in columns in a non-rigid carbon fiber
material under pre-compression through thermally controlled
contraction, by pre-forming to a predetermined engagement angle and
by segmented wedges with combined angles achieving 56.degree. flex
angle and fully engaging the non-rigid carbon fiber at a
predetermined lock-out angle.
The headings provided herein are for convenience only and do not
necessarily affect the scope or meaning of the claimed embodiments.
Further, the drawings have not necessarily been drawn to scale. For
example, the dimensions of some of the elements in the figures may
be expanded or reduced to help improve the understanding of the
embodiments. Moreover, while the disclosed technology is amenable
to various modifications and alternative forms, specific
embodiments have been shown by way of example in the drawings and
are described in detail below. The intention, however, is not to
limit the embodiments described. On the contrary, the embodiments
are intended to cover all modifications, equivalents, and
alternatives falling within the scope of the embodiments.
DETAILED DESCRIPTION
Various examples of the devices introduced above will now be
described in further detail. The following description provides
specific details for a thorough understanding and enabling
description of these examples. One skilled in the relevant art will
understand, however, that the techniques discussed herein may be
practiced without many of these details. Likewise, one skilled in
the relevant art will also understand that the technology can
include many other features not described in detail herein.
Additionally, some well-known structures or functions may not be
shown or described in detail below so as to avoid unnecessarily
obscuring the relevant description.
The terminology used below is to be interpreted in its broadest
reasonable manner, even though it is being used in conjunction with
a detailed description of some specific examples of the
embodiments. Indeed, some terms may even be emphasized below;
however, any terminology intended to be interpreted in any
restricted manner will be overtly and specifically defined as such
in this section.
FIG. 1A illustrates a fiber-reinforced composite material assembly
10 with tunable anisotropic properties shown in a planar, un-flexed
configuration in accordance with an embodiment of the present
technology. FIG. 1B illustrates the assembly 10 in solid lines in a
flat, relaxed position, and in phantom lines in an upward
deflection configuration and a downward deflection configuration.
The assembly 10 has a first layer 12 of fiber-reinforced composite
material fixedly and permanently joined with a second layer 14 of
durable, rigid substrate (i.e., polycarbonate, nylon, plastic,
metal, rigid fiber-based material, elastomer, etc.) whose flexural
modulus is greater than approximately 20,000 psi. The joined
assembly 10 is a bendable planar assembly, which is described
herein with reference to the spatial orientation as shown in FIG.
1A. Accordingly, the first layer 12 is shown in FIGS. 1A and 1B as
a top layer, and the second layer 14 is shown as a bottom layer. It
is noted that the terms "top" and "bottom" are used for purposes of
convenience to discuss orientation, and it is to be understood that
the assembly can be positioned in other spatial orientations, such
as an inverted orientation to that shown in FIG. 1A, so that the
first layer 12 is below the second layer 14. Alternatively, the
assembly 10 can exist in a contoured shape.
The assembly 10 is illustrated in FIG. 1A as a rectangular segment
with opposing side edges 16 extending between opposing ends 18. The
first and second layers 12 and 14 are fixedly joined together along
a plane defined by a longitudinal axis 20 and a lateral axis 22
perpendicular to each other. The assembly 10 is shown in a flat,
planar, relaxed position (i.e., in a neutral orientation) wherein
the longitudinal and lateral axes 20 and 22 are parallel to a
neutral plane extending through the assembly 10. The assembly 10 is
configured in at least one embodiment as an
anisotropically-flexible beam, such that the assembly 10 can be
bent away from the relaxed position in a first direction (i.e.,
upwardly) about the lateral axis 22 with the opposing ends 18 move
upwardly. The illustrated assembly 10 has a relatively low bending
resistance to bending forces that cause the assembly 10 to bend
upwardly, as seen in FIG. 1B. The beam defined by the assembly 10
is also constructed to bend slightly away from the relaxed position
in a second direction opposite the first direction (i.e.,
downwardly), such that the opposing ends 18 move downwardly. In
this downwardly bending condition, however, the assembly 10 has a
substantially higher resistance to bending forces that cause the
assembly to bend downwardly. The joined, fiber-reinforced composite
assembly 10 can be tuned to be flexible and easily bendable in the
first direction, but being rigid and inflexible to bending in the
opposite direction.
The first layer 12 can be configured to control bending
characteristics of the assembly 10 in a selected direction, (e.g.,
bending downwardly). In one embodiment, the first layer 12 of the
assembly 10 is made of a material having a tensile modulus that is
substantially greater than the material's compressive modulus. As
discussed herein, reference to a material's modulus (tensile or
compressive modulus) is referring to the modulus of elasticity of
the material in tension and/or compression. The first layer 12 can
be a fiber-reinforced composite material having unidirectional
fibers or interlaced fiber encapsulated and/or impregnated in a
selected flexible matrix configured so the composite material alone
is flexible and pliable or non-rigid. The fibers in the first layer
12 can be inorganic fibers (e.g., carbon fibers, glass fibers,
ceramic, fibers, metal fibers, other fibers, and/or combinations
thereof), organic or synthetic fibers (e.g., polymer fibers such as
polyamides, polyesters, or combinations thereof), natural fibers,
and/or combinations thereof. The material of the first layer 12 can
be configured such that the assembly 10 can exhibit strain
stiffening behavior. Accordingly, the rate of stiffening in the
material can increase in response to increased strain. This
configuration provides an assembly with asymmetric flexural
characteristics.
In one embodiment, the first layer 12 can be a woven, carbon
fiber-based composite material having warp fiber bundles 24
substantially parallel to each other and the side edges 16. The
warp fiber bundles 24 are woven with weft fiber bundles 26, wherein
the weft fiber bundles 26 substantially parallel to each other and
at a selected angle relative to the warp fibers 24 and/or the side
edges 16. In the illustrated embodiment of FIG. 1A, the warp and
weft fiber bundles 24 and 26, respectively, are woven at
approximately a 90-degree orientation relative to each other,
although the woven fibers 24 and 26 can have different fiber
orientations relative to each other. The first layer 12 may be made
of one or more sheets of a tunable, non-rigid fiber-reinforced
composite material. The first layer 12 can be configured with
matrix material and plurality of fibers, such that the first layer
is orthotropic. In one embodiment, the first layer 12 is made of a
stretchable fiber-based composite material, such as the material
disclosed in U.S. patent application Ser. No. 15/135,455, titled
Stretchable Fiber-Based Composite Material, filed Apr. 22, 2016,
and which is incorporated herein in its entirety by reference
thereto. The assembly 10 can also include tunable fiber-based
composite materials with binder-enhanced properties, such as the
materials as described in U.S. patent application Ser. No.
15/179,949, titled Composite materials with Binder-Enhanced
Properties and Methods of Production Thereof, filed on Jun. 10,
2016, which is incorporated herein in its entirety by reference
thereto.
The assembly 10 can be constructed as a laminate material by
combining a carbon fiber epoxy plate that defines the second layer
14 with a fiber reinforced nitrile butadiene rubber and
thermoplastic polyurethane film that defines the first layer 12.
The strengths and stiffness of fibrous composite materials in the
first layer 12 are dependent on the properties of the type of fiber
used, the orientation of the fiber, and the resin matrix used to
encapsulate and/or impregnate the fibers. In one embodiment, the
material used in the first layer 12 can be a nitrile butadiene
rubber impregnation with thermoplastic polyurethane films. Unlike
the first layer 12, the second layer 14 is made of a material that
has a tensile modulus substantially the same as its compressive
modulus. The second layer 14 can be a rigid carbon fiber epoxy
plate. Other types of materials can be used in the second layer,
such as steel, stainless steel, titanium, aluminum, other metal
material, polycarbonate, polyamide, polyurethane, low density
polyurethane, nitrile rubber, butyl rubber, and combinations
thereof. The compressive modulus of the material used in the second
layer 14 must be greater than the compressive modulus of the
material used in the first layer 12 to provide the fiber-reinforced
composite joined assembly 10 in the form of an
anisotropically-flexible beam with the necessary anisotropic
properties in compression and tension. In one embodiment, the
second layer 14 can comprise a plate with a modulus of elasticity
in the range of approximately 30 ksi-40,000 ksi. In another
embodiment, the first layer 12 can be a carbon fiber layer
impregnated or encapsulated with a resin matrix at 100% modulus in
the range of approximately 5 psi-5,000 psi. In other embodiments,
the matrix of the first layer 12 can be formed of thermoplastic
polyurethanes, thermoplastic elastomers, thermoplastic polyolefins,
silicone, acrylates, polyamides, polyurethanes, nitrile and butyl
rubbers, and styrenic block copolymers. The matrix material can be
selected or configured to have a range of matrix properties, such
as a modulus of elasticity in the range of approximately 5-3,000
psi. In another, embodiment the matrix can have a modulus in the
range of approximately 5-2000 psi. In another, embodiment the
matrix can have a modulus in the range of approximately 5-1000 psi.
In another, embodiment the matrix can have a modulus in the range
of approximately 20-500 psi. In another, embodiment the matrix can
have 50-500 psi In yet another embodiment, the matrix can have a
modulus in the range of approximately 50-300 psi. The two layers 12
and 14 of the assembly 10 in the illustrated embodiment are
laminated or otherwise joined together under 200.degree. F. to
375.degree. F. for about ten minutes or less to form an asymmetric
beam that has high bending stiffness (moduli) in one bending
direction and a low bending stiffness in the opposite direction. In
other embodiments, the two layers 12 and 14 could be joined with
other adhesive materials or using other laminating techniques.
FIG. 2 is an illustration showing, by way of example, a three-point
bend on the assembly 10 with the first and second layers 12 and 14,
respectively, forming an anisotropically-flexible beam having two
different moduli. The assembly 10 is shown in FIG. 2 in an inverted
position compared to FIG. 1B and corresponding to a downward
bending configuration as referenced above, such that the second
layer 14 is in compression, and the first layer 12 is in tension.
The assembly 10 is very resistant to the downward bending loads
because the fiber-reinforced composite material forming the first
layer 12 has a very high tensile modulus, so when the warp and/or
weft fibers 24, 26 (FIG. 1A) are in tension, the fibers
substantially prevent or resist excessive bending. In one
embodiment, the first layer 12 has a tensile modulus in the range
of approximately 3-5,000 ksi. In another embodiment, the first
layer 12 can have a tensile modulus in the range of approximately
3-2,000 ksi, 5-2,000 ksi, 25-1500 ksi, or 100-2,000 ksi,
When the assembly 10, however, is bent in the opposite direction so
as to put the second layer 14 in tension, the assembly 10 is more
flexible. FIG. 3 is an illustration showing, by way of example, the
assembly 10 as a simple beam being bent upwardly in three-point
bending (i.e., in the opposite direction as shown in FIG. 2) with
the same force as applied in FIG. 2. In FIG. 3, the first layer 12
is now in compression, and the second layer 14 is in tension. The
composite fiber material of the first layer 12 has a low
compressive modulus and the fibers elastically buckle under
compression, such that the flexibility allows for a much greater
bending of the assembly 10 in the upward direction in response to
the same bending loads as the inverted response. In one embodiment,
the compressive modulus of the first layer 12 is sufficiently low
such that it provides a negligible resistance to bending of the
assembly 10 in the upward direction (i.e., when the first layer 12
is in compression). Accordingly, the assembly 10 provides an
anisotropically-flexible beam with greater resistance to bending in
one direction (i.e., when the first layer 12 is in tension) than in
the other direction (i.e., when the first layer 12 is in
compression and elastically buckles).
FIG. 4 is an enlarged partial cross sectional view taken
substantially along line 4-4 of FIG. 1A showing the first and
second layers 12 and 14 of the assembly 10 in accordance with an
embodiment of the present technology. The illustrated first layer
12 includes a non-rigid carbon fiber-reinforced composite material
having two layers of fiber materials joined together. The thickness
of the first layer 12 is substantially the same as the thickness of
the second layer 14. In other embodiments, the first and second
layers 12 and 14 can have different thicknesses. The first layer 12
is permanently affixed to the second layer 14 at a middle interface
area 30. The illustrated assembly 10 can be configured with a
neutral bending plane 32 substantially parallel to the interface
area 30. When the assembly 10 is bent upwardly, so the first layer
12 is in compression with the fibers buckling, the first layer 12
provides a substantially negligible resistance to bending. The
neutral bending plane 32 is close to the middle of the second layer
14, which provides low bending resistance to allow the assembly 10
to bend upwardly. When the assembly 10, however, is bent downwardly
so the first layer 12 is in tension, the neutral bending plane 32
moves closer to the interface area 30. The fibers in the first
layer 12, when in tension, provide much more bending resistance
relative to downward bending of the assembly 10.
The assembly 10 can be tuned by selecting and controlling the
materials of the first and second layers 12 and 14 to provide the
anisotropic bending characteristics. For example, the
characteristics can be controlled by changing the number of sheets
of fibers in the laminate in the first layer, its matrix material,
the weave of the fibers, the interstitial layer material, the film
material, fiber type(s), fiber content, areal density of the
fiber(s), etc. When the second layer 14 is a rigid composite fiber
material, the bending characteristics of the second layer 14 can
also be tuned by controlling the constituents of the layer,
including the layers of fiber, weave, matrix, etc. In other
embodiments, the second layer 14 can be made of other materials,
such as metals, plastics, or other material selected for tuning of
the layer or the assembly. In one embodiment, the second layer 14
can be formed of shaped and/or perforated metal, plastic, or other
suitably rigid material.
Different configurations and combinations of carbon fiber materials
can be advantageously used in constructing the
anisotropically-flexible assembly. FIGS. 5-8 are graphs 34, 36, 38,
40 showing the differences between flexural moduli in exemplary
testing configurations. The x-axes represent strain in units of
inches per inch (in/in). The y-axes represent stress in pounds per
square inch (psi).
Referring to FIG. 5, the flexural modulus (i.e. bending stiffness)
for the non-rigid side (i.e., the first layer 12) in compression is
17,700 psi, and the non-rigid side in tension is 117,000 psi, which
is roughly a 6.6:1 change its flexural modulus based on bending
direction. Referring to FIG. 6, a configuration that uses a single
layer of non-rigid carbon in the first layer 12 has a flexural
modulus for the non-rigid side in compression of 177,000 psi and
the non-rigid side in tension of 808,000 psi, which is roughly a
4.6:1 change in flexural modulus based on bending direction.
Referring to FIG. 7, shifting the fabric in the first layer 12,
such that the angle between the warp and weft fibers 24 and 26
(FIG. 1) is greater or less than 90 degrees, can increase the
flexural modulus of elasticity in both the non-rigid compression
and tension values to 348,000 psi and 1,240,000 psi respectively,
which is roughly a 3.6:1 change in flexural modulus based on
bending direction. Referring to FIG. 8, the shifted fabric in
bending was tested to evaluate the transverse direction of the beam
bending with little difference with the shifted fabric at 70
degrees to the off-axis, whether in tension or compression with
flexural modulus values of 27,700 psi and 24,400 psi
respectively.
FIG. 9 illustrates a graph 42 showing the stress-strain
relationship of an embodiment of the assembly having a two layer,
non-rigid carbon-fiber fabric configuration in compression and in
tension. The graph illustrates the stress-strain relationship of
the assembly with the first layer 12 in compression and the
initiation of the elastic deformation and buckling of the fibers in
the non-rigid carbon fiber material. The flexural rigidity in the
range of motion can be tuned through variation in moduli
combinations. The moduli can be changed based on resin matrix
moduli and fabric weave pattern. FIG. 10 illustrates controlled
buckling in the first layer 12 formed by a non-rigid carbon fiber
material under compression. By changing the matrix modulus, the
buckling resistance will change, therefore changing the compression
modulus of the material. The matrix moduli can vary between less
than 5 psi to greater than 3,000 psi. The matrix content can also
be controlled by coating, impregnating, or encapsulating the fibers
with different quantities of matrices. For example, a matrix
material can be a dispersion that completely coats, impregnates or
encapsulates all of the fibers with a low modulus resin and
provides a weight gain of up to 50%, and conversely a dry fiber
with no binder can be used as the other extreme. This range
provides a different effective modulus in tension and compression
that is offered because of a binder that fuses the fiber bundles
together in random locations, while the other locations are
considered to be dry fiber, whereas the air in the space is the
lower modulus matrix.
The compression modulus also changes based on the weave density in
the fabric combined with the resin matrix modulus. Weave densities
change the spacing of the transverse tows, thereby changing the
column length for buckling in the longitudinal direction. For
example, a 268 gsm fabric will have approximately 16 tows per inch,
which yields a tow spacing of 0.0625 inches and with a 2.times.2
twill pattern gives a 0.125 inch column length. A 200 gsm fabric
will be 12.5 tows per inch, which yields a tow spacing of 0.080
inches and with a 2.times.2 twill pattern gives a 0.160 in. column
length. Shorter column lengths increase the compression modulus and
longer column lengths decrease the modulus. The size of the fiber
tows can also be construed to offer columnar stiffness, whereas a
fiber tow size of 24K would have higher columnar stiffness than a
12K and whereas a 3K would offer a lower columnar stiffness than
the 12K and so on. The tow size effectively changes the columnar
diameter based on the size of the tow.
Referring to Table 1 (below), two sheets of 268 gsm fabric
2.times.2 twill with 6% binder content joined to a rigid carbon
fiber composite substrate has a flexural modulus for E100 on the
non-rigid side compression is 59,700 ksi and the non-rigid side in
tension is 454 ksi, which is roughly a 7.6:1 change in modulus
based on bending direction. A configuration that uses a single
layer of non-rigid carbon in the first layer 12 has a flexural
modulus for E099 on the non-rigid side compression of 295.8 ksi and
the non-rigid side in tension of 875.7 ksi, which is roughly a
2.96:1 change in modulus based on bending direction.
Shifting the fabric (see FIG. 8) can increase the modulus in both
the non-rigid side compression and tension values to 348 ksi and
1,240 ksi respectively, which is roughly a 3.6:1 change in modulus
based on bending direction.
TABLE-US-00001 TABLE 1 1 Layer SCF, 2 Layer SCF, 1 Layer SCF, 2
Layer SCF, 1 Layer SCF, 2 Layer SCF, 20 mil HCF 20 mil HCF 20 mil
PC 20 mil PC 20 mil Ti 20 mil Ti E099 E100 E274 E275 E276 E277
Flexural 875.666 454.009 209.142 172.011 3703.806 1506.468 Modulus,
Non- rigid Side in Tension 1.5- 2% Strain (ksi) Flexural 295.846
59.670 55.994 26.941 2930.097 808.471 Modulus, Non- rigid Side in
Compression 1.5-2% Strain (ksi) Modulus Ratio 2.960 7.609 3.735
6.385 1.264 1.863
Also a 268 gsm fabric 2.times.2 twill with 6% binder content
comparing different rigid substrates and 1 and 2 sheets of
non-rigid carbon fiber demonstrates the versatility and range of
control of modulus levels one can obtain. Referring again to Table
1, a single layer of 268 gsm fabric 2.times.2 twill with 6% binder
content forming the first layer 12 joined to a polycarbonate
substrate forming the second layer 14 has a flexural modulus for
E274 with the non-rigid side in compression of 56 ksi and the
non-rigid side in tension of 209.1 ksi, which is roughly a 3.7:1
change in modulus based on bending direction. In comparison, E276
in Table 1 having a single layer of 268 gsm fabric 2.times.2 twill
with 6% binder content forming the first layer 12 joined to a
titanium substrate forming the second layer 14 has a flexural
modulus with the non-rigid side in compression of 2930 ksi and with
the non-rigid side in tension of 3703.8 ksi, which is roughly a
1.3:1 change in modulus based on bending direction.
Referring to Table 1, two sheets of 268 gsm fabric 2.times.2 twill
with 6% binder content forming the first layer 12 joined to a
polycarbonate substrate forming the second layer 14 has a flexural
modulus for E275 with the non-rigid side compression of 26.9 ksi
and the non-rigid side in tension of 172 ksi, which is roughly a
6.4:1 change in modulus based on bending direction compared to E277
in Table 1, two sheets of 268 gsm fabric 2.times.2 twill with 6%
binder content forming the first layer 12 joined to a titanium
substrate forming the second layer 14 has a flexural modulus with
the non-rigid side in compression of 808.5 ksi and with the
non-rigid side in tension of 1506.5 ksi, which is roughly a 1.86:1
change in modulus based on bending direction.
In a further embodiment, the assembly 10 can be constructed as a
resin matrix and fiber weave material. The weave pattern on the
first layer 12 with a low compression modulus has one compression
modulus in one direction and a different compression modulus in a
direction transverse to the first modulus in the same plane. This
configuration allows the anisotropically-flexible beam to be flexed
differently in the two planes. For example, a 2.times.2 twill
fabric can have 16 tows per inch in the longitudinal direction and
12 tows per inch in the transverse direction, thereby changing the
columnar spacing that provides two different compression modulus by
different buckling points.
In a still further embodiment, the assembly 10 can be constructed
as a weave pattern with differing compression moduli based on weave
direction. This material changes layer orientations of the material
of the first layer 12 to provide variable stiffness. FIGS. 11A and
11B are illustrations showing, by way of example, changes in fiber
orientation when material is strained along the longitudinal axis
of a simple beam. As disclosed in Applicant's U.S. patent
application Ser. No. 15/135,455, when the fibers undergo tensile
strain, the fibers align themselves in the tension direction;
conversely, when the fibers are in compression and they shift into
a more transverse direction causing the compression modulus to
shift lower. When the assembly 10 is configured with the first
layer 12 having a shifted fabric arrangement, the dynamic fiber
orientation during flexing causes the beam to become stiffer as the
beam is flexed. The assembly 10 becomes stiffer as the deflection
increases. Accordingly, the asymmetric beam material composition
can be modified or tuned to change performance. The various
embodiments utilize a composite material design with combinations
of high tensile modulus in tension and low compression modulus
material in compression to provide a highly flexible one way beam,
and conversely a highly rigid beam with opposite loading.
The assembly 10 forming the anisotropically-flexible beam can be
used in a wide variety of products or applications. For example,
the assembly 10 can be used to form a component in an article of
footwear 50 shown in FIG. 12. It is known that the potential for
injury to a wearer's foot often increases with increased
flexibility. The protection of the foot via the footwear's sole
assembly can be reduced through the use of non-rigid material that
allows the traditional shoe to have greater flexibility. To counter
such potential reduced protection, the assembly 10 can be used as a
component of the footwear's sole assembly or as an insole that
provides anisotropic bending and that can provide a rigid, thin
substrate layer that can laterally dissipate forces applied to the
bottom or plantar side of the foot, thereby helping to protect it
from injury. The assembly 10 can also be incorporated into footwear
to provide increased flexibility substantially without sacrificing
stability and protection. The resulting combination can decrease or
even eliminate user fatigue by incorporating an
anisotropically-flexible sole component into the footwear.
The illustrated article of footwear 50 has an upper 52 shaped to
receive a foot of a wearer. The footwear 50 can be a shoe,
including a dress shoe, casual/life-style shoe, running shoe,
cleated shoe, other athletic shoe, Oxford shoe, or other type of
shoe. The footwear 50 can also be a boot, sandal, or other the
like. The upper 52 is fixedly attached along the bottom margin to a
sole assembly 54. The illustrated sole assembly 54 has one or more
internal joined plate assemblies 56 made of the assembly 10 of FIG.
1A in accordance with an embodiment of the present technology. FIG.
13 is a schematic cross-sectional view of the sole assembly 54 with
the joined plate assembly 56 shown relative to a wearer's foot. The
illustrated sole assembly 54 includes an outsole 58 attached to the
bottom portion of a midsole 60. The sole assembly 54 can include an
insole board 62 attached to the top of the midsole 60 and
positioned to support the upper 52. The plate assembly 56 is
attached to the midsole 60 and can be shaped and sized to extend
fully underfoot from a forefoot portion 64 through an arch portion
66 to a heel portion 68. The plate assembly 56 can be a one piece,
full foot plate, although the plate assembly 56 in other
embodiments can include one or more segments positioned in the
forefoot portion 64, arch portion 66 and/or heel portion 68. The
segments can be connected to each other or spaced apart when
multiple segments are provided in the sole assembly 54.
The plate assembly 56 is shown embedded within the midsole 60. The
plate assembly 56, however, can be positioned between the bottom of
the midsole 60 and the outsole 58. In another embodiment, the plate
assembly 56 can be positioned between the insole board 62 and the
midsole 60. In yet another embodiment, the plate assembly 56 can be
positioned atop the midsole 60 forming the insole board 62.
The plate assembly 56 is made with the joined construction having
the anisotropic bending behavior during flexing to provide a low
bending resistance during flexing of the sole in the dorsal flex
direction (i.e., upward bending) and a high bending resistance in
the plantar flex direction (i.e., downward bending). The
anisotropically-flexible plate assembly 56 includes a dorsal layer
70 and a plantar layer 72, both of which are constructed from two
different types of flexible material. The dorsal layer 70 is
defined by the first layer 12 of the assembly 10 as discussed
above, and a plantar layer 72 defined by the second layer 14 of the
assembly 10 as discussed above. The material used in the dorsal
layer 70 has a low modulus of elasticity in compression and a high
modulus of elasticity in tension. The dorsal layer 70 is tuned to
limit longitudinal deflection in the plantar direction. The
material used in the plantar layer 72 has a rigid material whose
modulus of elasticity can be greater than, less than, or equal to
the modulus of elasticity in tension of the flexible material of
the dorsal layer 70. The plate assembly 56 is configured to provide
simultaneous improvements in stability, flexibility, and protection
not currently available in footwear.
Conventional footwear soles traditionally focus in one area of
improvement at the sacrifice of another. For instance, a running
shoe may increase flexibility and cushioning at the sacrifice of
stability and protection. The increased flexibility is commonly
achieved through outsole and midsole design that provides segments
in the sole in flexing regions of the shoe. While this does
increase flexibility, the torsional stiffness can be considerably
reduced, and the plantar flex protection can be substantively
sacrificed. Another instance is a hiking boot that often sacrifices
flexibility for increased protection and stability. The use of
rigid materials in the construction of the sole of the hiking boot
increases the stiffness while preventing foot bruising from rocks
or roots on the hiking trail.
The assembly 10 in the form of the plate assembly 56 of the present
technology allows for highly tunable bending flexibility without
the sacrifice of the stability and protection. In one embodiment,
the dorsal layer 70 is laminated or otherwise securely joined to
the plantar layer 72, such that when the dorsal layer 70 is under
compression when bending in the dorsal flex direction, the dorsal
layer 70 has a low compression modulus and can bend easily.
Accordingly, the plate assembly 56 does not provide too much
dorsiflexive bending resistance, such as during the transition from
the flat foot stage of a stride through toe-off stage during which
the wearer's foot naturally bends at the metatarsal joints.
Conversely, when forces on the sole assembly 54 bend the plate
assembly 56 in the opposite, plantar flex direction, the dorsal
layer 70 is under tension and has a high modulus that can
significantly resist such bending. The laminate construction of the
plate assembly 56 also provides stability during a wearer's gait
cycle by controlling the dorsiflexive motion that helps eliminate
the foot's tendency to want to roll inward or outward (pronate and
supinate). The increased flexibility helps reduce the forces
required by the foot to flex the footwear 50, thereby reducing
fatigue which can help increase stability.
During use of the footwear 50, such as running, walking, hiking,
climbing ladders, etc., the sole assembly 54 is often subjected to
uneven surfaces such as rocks, sidewalk cracks, sticks, ladder
rungs, or other sources of unevenness that can create localized
forces applied to the bottom of the wearer's foot. These localized
forces can bruise the foot or cause soreness or other discomfort.
The sole assembly 54 with the integrated anisotropic plate assembly
56 provides a rigid support that laterally displaces the localized
forces through a high resistance to bending in the plantar flex
direction.
In another embodiment illustrated in FIG. 14, an insole 76
insertable into the footwear's upper 52 (FIG. 12) can include a
plate assembly 74 with one or more portions having a construction
substantially similar to the assembly 10 discussed above. The
insole 76 can be removably inserted within the upper 52 or it can
be fixedly attached to the bottom portion of the upper 52. The
insole 76 can be a generally planar insole. In another embodiment,
the insole 76 can be a molded orthotic insole that at least
generally conforms to the shape of a wearer's foot. The insole 76
can be a full-length insole extending under the forefoot, arch, and
heel portions of the wearer's foot. In other embodiments, the
insole 76 can be less than a full length insole, such as a
three-quarter-foot or half-foot insole.
The plate assembly 74 of the insole 76 has a dorsal layer 78
defined by the first layer 12 of the assembly 10 and that includes
a flexible material exhibiting a modulus of elasticity tuned to
limit longitudinal deflection in the plantar direction. The insole
76 also has a plantar layer 80 fixedly attached to the dorsal layer
78 and configured to fit snuggly against the top of the footwear's
sole assembly. The plantar layer 80 includes the woven fibers
within a matrix comprising another flexible material exhibiting a
modulus of elasticity that is comparatively higher than the modulus
of elasticity of the flexible material of the dorsal layer 78. The
bottom of the insole 76 comprising the plantar layer 80 can be
configured to generally provide cushioning of the foot, whilst the
top of the insole 76 comprising the dorsal layer 78 protects the
foot against chafing, as well as providing a lesser degree of
cushioning. Alternatively, the insole 76 could be constructed with
just a single layer of rigid substrate on the dorsal side and two
sheets or more of a flexible composite substrate on the plantar
side that provides further flexibility. In one embodiment, the
insole 76 can have one or more durable cushioning and/or wear
sheets attached to the dorsal layer 78 and/or the plantar layer 80
to provide additional comfort for the wearer's foot during use.
In the embodiments illustrated in FIGS. 12-14, the plate assembly
56 and the insole 76 are generally planar assemblies with a flat
neutral orientation when the bending forces are not acting on the
assembly 10. Accordingly, when the assembly 10 is in the neutral
orientation (shown in a substantially horizontal orientation), the
dorsal layer 70/78 and the plantar layer 72/80 are substantially
not in tension or compression. When bending forces are applied to
the flat assembly 10 to cause bending away from horizontal, the
dorsal layer 70/78 and the plantar layer 72/80 are in compression
or tension depending on the direction in which the assembly 10 is
bent away from the neutral orientation.
The assembly 10 with the directional bending stiffness can be
utilized in other applications to achieve the benefits of a low
resistance to bending in one direction and a high resistance to
bending in the other direction. For example, the assembly 10 could
be incorporated into athletic equipment to improve the athlete's
on-field performance and reduced fatigue by incorporating such
materials into their equipment. The assembly 10 could be
incorporated into baseball gloves and/or soccer goalie gloves. When
glove fingers, for instance, are pulled in the inward direction,
the glove fingers are easily flexed, while if the fingers are bent
backwards toward the back of the hand, the fingers of the glove are
more rigid to resist the bending. A baseball catcher or soccer
goalie, for instance, could integrate the material into their
respective forms of gloves, whereby the increased stiffness is used
advantageously to help cushion impact, whilst the increased
flexibility aids with gripping action and easy closure. The
asymmetric beam configuration of the assembly 10 can protect an
athlete, for instance, against hyperextension of their fingers when
stopping a soccer ball or a baseball glove that allows easy
closure, as well as provide stiffness in glove finger areas with
which to stop balls thrown at high velocity. The asymmetric beam
configuration of the assembly 10 could also be incorporated into
joint areas of prosthetics, into back or articulating braces and
supports, or into other medical devices or medical appliances.
The assembly 10 in accordance with other embodiments can be used as
a protective member that protects a user's excessive bending in an
undesired bending, while allowing bending in the opposite
direction. For example, movement of the limbs and joints of the
body outside of their expected range of motion is known as
hyperextension, which refers to movement beyond normal limits of
angular, rotational or gliding motion, depending upon the
anatomical structures involved. The assembly 10 can also be used in
footwear, such as soccer, rugby, or football shoes, configured to
flex and bend with a user's foot in one direction during a normal
running or walking stride, while maintaining stiffness and
resistance to bending in the opposite direction, such as while
kicking a soccer ball, rugby ball, or football. Accordingly, when a
player kicks the ball, the shoe remains substantially stiff so as
to impart greater loads or forces to the ball. One or more
embodiments of the assembly 10 can be specifically tuned for
particular athletic events, and/or for particular athletes or other
users. For example, the assembly 10 could be used in footwear and
tuned based upon an athlete's particular individual musculoskeletal
characteristics, such as metatarsophalangeal (MTP) range of motion
and extension velocity while running, so as to provide a
progressive bending stiffness for the athlete to enhance the
athlete physical performance. For example, footwear for an athlete
with a lager MTP extension could include an assembly 10 tuned to
provide a progressive increase in bending stiffness to help
maximize individual performance. Tuning of shoes for stiffness to a
runner's particular characteristics can be provided to maximize
performance. Assembly 10 will adjust the stiffness to different
phases of a running (acceleration, sprinting, and jogging) to
optimize performance. For example, a shoe with a progressive
stiffness that exhibits low gearing in the initial acceleration and
transitions to a higher gearing at the top speed phase of the
run.
Hyperextension can result in physical injury due to the increased
stress and forces applied to ligaments and connective tissues.
Hyperextension often occurs in concert with physical or sports
activities, but can also develop over time through chronic or
repetitive overuse of some part of the body. For example, lateral
epicondylitis or "tennis elbow," is caused by the repetitive use of
the extensor muscles of the forearm and is commonly associated with
playing tennis, but the condition has also been called "washer
woman's elbow," reflective of an age when clothes washing was
performed as a manual vocation. On the same note, chondromalacia
patellae or "runners knee," is the increased deterioration and
breakdown of the cartilage under the kneecap due to an overworking
of the knee, often due to running, but could be attributed to
gymnastics, cycling, horseback riding, ballet, and even swimming.
Finally, metatarsophalangeal joint sprain or "turf toe," occurs
when the toes of the foot are hyperextended, as often occurs in
professional sports that are played on artificial turf, especially
football, but has been observed in soccer, rugby, and volleyball,
and even in non-field sports, like basketball and taekwondo.
Taking "turf toe" as a specific example, the risk of incurring a
metatarsophalangeal joint sprain increases with the angle of
longitudinal deflection at the metatarsal phalangeal joint. A
sprain can occur with the hyperextension of any of the toes,
although the big toe normally suffers injury, as the bulk of
forward dorsiflexive motion is borne by that toe. This type of
injury with the metatarsal phalangeal joint region of the foot
includes the ligaments and connective tissues that join the ball of
the foot with the toes. The metatarsal phalangeal joint can be
injured if the back of the calf is pushed forward whilst the knee
and toes are in contact with the ground. Injury can also happen
when the cleats of an athletic shoe grip into artificial turf and
fail to release the foot when the individual is running or walking.
The forward momentum of the body causes the foot to bend too far
forward at the metatarsal phalangeal joint while the toes are still
held firmly in place by the turf, resulting in hyperextension of
the toes.
The risk of incurring injury due to hyperextension can be
significantly decreased through the use of protective equipment
that cushions from damage or restricts or limits the movement of
the various limbs and joints of the body, whether elbows, wrists,
fingers, knees, ankles, toes, hips, or other anatomical structures,
to their normal range of expected motion. For instance, existing
measures for protecting against turf toe are lacking. For example,
U.S. Pat. No. 5,772,621 discloses a turf toe brace that includes a
flexible boot adapted for snugly anchoring the brace to a foot, an
elongate non-stretchable strap joinable to the boot, and a toe loop
that is joined to the strap opposite the boot. In use, the strap
passes under the foot and is connected to the boot in such a manner
as to pull downwardly on the big toe and help prevent
hyperextension, whilst the other four unrestrained toes remain at
risk of hyperextension. As well, the brace requires enough
clearance in the ankle region to fit within a shoe. Last, the strap
could become undone during use, thereby obviating any protective
benefits.
U.S. Patent Appl. Pub. No. 2012/0240431 discloses a turf toe
terminator, which is a semi flexible shoe insert that is inserted
into a cleat or sneaker, or is created as part of a shoe, to help
prevent injury due to hyperextension of the big toe. A nylon strap
is attached to the toe and heel of a polypropylene plastic shoe
insert using nylon string. The nylon strap is attached under
tension to generate an inverted arch in the shoe insert, which
helps provide support to a hyperextended big toe. During use, when
the toes are forced upward, the nylon strap of the shoe insert
prevents the toes from extending to hyperextension and transfers
pressure from the toes to the heel of the shoe by pushing downward.
However, the strap is attached to the shoe insert with string and
is therefore susceptible to breakage. Moreover, the shoe insert is
primarily focused on protecting the big toe with only incidental
hyperextension prevention being provided to the other toes of the
foot.
Accordingly, there is a need for a shoe, shoe insert or foot
support that will safeguard all of the toes of the foot from
hyperextension while allowing bending of the toes through the
normal range of motion without reaching the point of
hyperextension. There is a further need for a protective equipment
that keeps body motion, not just the toes, within a normal range of
expected motion without restricting normal free movement up to the
limits of hyperextension.
At least one embodiment of the assembly 10 of the present
technology is configured to significantly decrease or eliminate the
risk of turf toe or other metatarsophalangeal joint sprain to all
of the toes by incorporating an anisotropically-flexible area into
the flex region 110 of the footwear under the metatarsal phalangeal
joints of the foot. The anisotropically-flexible area is
incorporated into a shoe insert, insole, midsole or outsole and is
separated into a dorsal side and a plantar side, both of which are
constructed from two different types of flexible material. The
material used in the plantar side has a variable modulus of
elasticity tuned to limit longitudinal deflection based on angular
deflection levels in the dorsal direction based on angular rotation
of the metatarsal phalangeal joint, that is, forward dorsiflexive
motion, while the material used in the dorsal side has a modulus of
elasticity that is comparatively higher than the variable modulus
of elasticity of the flexible material of the plantar side.
One embodiment provides a tuned plate assembly made of the assembly
10 and incorporated within the shoe sole assembly or provided as an
insole shaped to fit within the bottom part of a shoe. The tuned
plate assembly 10 has an anisotropically-flexible area situated for
placement under the metatarsal phalangeal joint region of the foot.
The assembly 10 provides a shoe sole and/or insole with a flexural
modulus that increases as a function of increasing bend angle
relative to the neutral orientation.
Furthermore, in the foregoing embodiments, the tuned plate assembly
may also be configured with a dorsal side exhibiting a variable
modulus behavior, such that the modulus increases as angular
rotation (dorsiflexion) of the metatarsal phalangeal joint region
occurs, where the mechanism creating the dorsal variable modulus is
a compressive layer engagement that coincides with dorsiflexion of
the metatarsal phalangeal joint.
The directional bending stiffness described herein can be utilized
in footwear-related applications, such as shoe inserts, articles of
footwear with a shoe insert, articles of footwear with a midsole,
articles of footwear with an outsole, and articles of footwear,
requiring a varying resistance to bending in the dorsal direction
based on angular rotation of the metatarsal phalangeal joint. The
directional bending stiffness can also be utilized in applications
that provide protective equipment to keep body movement within a
normal or constrained range of expected motion without restricting
normal, free movement up to the limits of hyperextension, such as
needed in the joint areas of prosthetics, back or articulating
braces and supports, and articulating braces.
FIG. 15 is a schematic illustration of a shoe insert 100 for an
article of footwear, in accordance with an embodiment of the
present technology. The shoe insert 100 is configured to
substantially block or prevent metatarsophalangeal joint sprain due
to hyperextension of the toes of a wearer's foot 102, thereby
significantly decreasing or even eliminating the risk of a toe
injury. The shoe insert 100 provides an anisotropically-flexible
area in the region under the metatarsal phalangeal joints of the
foot 102. The shoe insert 100 can be shaped to fit within a shoe,
or as part of the shoe's sole assembly. The shoe insert 100 could
be configured as another article of footwear, for instance, as a
sock or foot sleeve. Alternatively, the anisotropically-flexible
area defined by the shoe insert 100 could be incorporated into a
midsole or outsole of a shoe's sole assembly to provide the same
type of hyperextension prevention.
The shoe insert 100 is a joined assembly having one or more layers
with a construction substantially similar to the assembly 10
discussed above. The shoe insert 100 has a dorsal (or
upward-facing) layer 104 that fits conformably and comfortably
against or adjacent to the bottom of the wearer's foot 102 and a
plantar (or downward-facing) layer 106 that fits snuggly against
the top of the shoe's sole or as part of the sole. The shoe insert
100 can be used with or in an article of footwear 50 discussed
above (FIG. 12). The plantar layer 106 generally provides
cushioning of the foot 102, and the dorsal layer 104 protects the
foot 102 against chafing, as well as providing a lesser degree of
cushioning.
The risk of incurring a metatarsophalangeal joint sprain increases
with the angle of longitudinal deflection at the metatarsal
phalangeal joint 108 of the foot 102 and often happens if
deflection exceeds approximately 56.degree.. The precise angle of
deflection that results in such a sprain, however, will depend upon
many factors, including foot placement and orientation, speed and
force of forward movement, physical structure of the individual's
foot, and any prior metatarsophalangeal joint sprains or foot
injuries. The shoe insert 100 is configured to counter undue
deflection that could lead to hyperextension of the metatarsal
phalangeal joint 108. The shoe insert 100 incorporates an
anisotropically-flexible area 110 situated for placement under the
metatarsal phalangeal joint 108 of the foot 102. In general,
anisotropic materials exhibit directionally-dependent properties,
such that the degrees of flexibility and stiffness differ depending
upon the axes at which they are measured.
In the shoe insert 100, the flexing of a shoe is measured in torque
where the shoe is flexed about the flex area 110 generally between
the forward and rear portions 116 and 118, and the resistance of
the shoe flex increases with flex angle due to increasing flexural
modulus. FIG. 16 is a graph showing the relationship of the
flexural modulus 124 as a shoe flex torque and angle of curvature.
The x-axis represents the bend angle of the shoe insert 100 in the
dorsal (upward) direction. The y-axis represents shoe flex torque
in Newton-meters (Nm) and the relationship of flexural modulus that
creates the increase in torque. The increase in flexural modulus
124 is caused by curved columns which are either formed through
applied stress (i.e. prebuckling) or weave crimp, as further
described infra, that are formed at a predetermined angle or
through controlled thermal contraction, which set a level of
maximum permissible angle rotation of the shoe sole about the flex
area 110. The increase in flexural modulus can thus be described as
the ratio of the secondary slope to the primary slope, where the
primary slope can be as low as 100 pounds per square inch (psi) and
the secondary slope can be as high as 33 million psi. Here, the
minimum ratio in a material is approximately 1.25:1 and the maximum
ratio is approximately 20:1. In addition, the primary slope can be
located between 0.degree. and 15.degree. and the secondary slope
can be located beyond approximately 60.degree.. Other ratios and
flex range locations are possible. For example, a shoe insert 100
can be configured with the material of the assembly having a ratio
of the secondary slope to the primary slope defining the flexural
moduli in the range of approximately 1.25:1 to 2.5:1. In another
embodiment, the ratio can be in the range of approximately 2:1 to
3:1, 2.5:1 to 4:1, 3:1 to 6:1, 5:1 to 10:1, 6:1 to 13:1, or 10:1 to
20:1.
The shoe insert 100 can use different types of flexible and
non-flexible materials that are combined to control the location
and orientation of the flex area 110. FIG. 17 is a cross-sectional
view showing the construction of the shoe insert 100 of FIG. 15,
wherein the dorsal layer 104 is formed of one or more rigid sheets
126 of material, while the plantar layer 106 is formed of one or
more flexible sheets 128 of material, exclusive of the flex area
110, with tunable rigid layers 112 of material formed in-between
the two rigid and non-rigid layers 126, 128. Alternatively, the
shoe insert 100 could be constructed with just a single layer of
materials, except for the flex area 110, that helps restrict
excessive bending of the wearer's foot.
The tunable rigid layers 112 of material have a construction
similar to the assembly 10 discussed above, but inverted, wherein
the tunable rigid layers 112 have a dorsal side 130 and a plantar
side 132. The material used in the dorsal side 130 has a modulus of
elasticity tuned to limit longitudinal deflection based on angular
rotation of the metatarsal phalangeal joint 108 in the dorsal
direction, that is, forward dorsiflexive motion. The material used
in the plantar side 132 has a modulus of elasticity that is
comparatively higher than the modulus of elasticity of the flexible
material of the dorsal side 130.
Referring again to FIG. 15, the flex area 110 is configured to have
an upwardly curved shape when the joined assembly 10 forming the
flex area 110 is in the neutral orientation. Accordingly, when the
entire shoe insert 100 is in a neutral configuration, the forward
portion 116 would be an angle of approximately 50-56 degrees (or
other selected angle) relative to the rearward portion 118. When
the forward and rearward portions 116, 118 are flat and coplanar
(FIG. 17), the fiber-based composite material on the plantar side
of the flex area 110 would not substantively resist bending until
reaching the 50-56 degree angle. The flex area 110 can be tuned and
configured to begin providing bending resistance as the flex area
110 reaches the 50-degree angle, and significantly increasing the
bending resistance as the flex area 110 approaches the 56-degree
angle, so as to effectively block or prevent the wearer's toes from
flexing past 56-degrees. The plantar side of the flex area 110,
however, would be in tension and would bias or urge the flex area
110 back toward the neutral orientation. This biasing of the shoe
insert toward the 50-56 degree angle could actually provide some
energy return to the wearer's foot during a stride cycle as the
foot approaches the toe-off phase, all while preventing over
bending and hyperextending of the metatarsal joints.
The flex area 110 is preferably situated for placement under
metatarsal phalangeal joints 108 (FIG. 15) to provide optimal
protection from hyperextension of the toes. In the average person,
the flex area 110 would be placed in the region located at about
70% of the total shoe insert length (measuring from the heel to the
toes). The rigid layers 112, that is, the areas outside of the flex
area 110 on the plantar aspect of the shoe insert 126, should
preferably be more rigid than the flex area 110, so as to help
prevent the plantar aspect of the foot 102 from flexing in the
areas outside of the flex area 110.
The shoe insert 100 lowers or eliminates the risk of incurring a
metatarsophalangeal joint sprain ("turf toe") by preventing
longitudinal deflection of the foot 102 at the metatarsal
phalangeal joint 108 beyond approximately 56.degree.. The shoe
insert 100 incorporates an anisotropically-flexible area 110 formed
using a fiber-reinforced composite material that exhibits a
different modulus of flexibility when a predetermined angle of
flexion has been reached. Flexing of the material beyond the
predetermined angle is limited or precluded, while preserving
pliability of the material within the predetermined angle. This
type of anisotropically-flexible area can be incorporated into
other forms of protective equipment intended to keep body movement
within a normal or constrained range of expected motion without
restricting normal free movement up to the predetermined angle,
such as in the joint areas of prosthetics, back or articulating
braces and supports, and articulating braces. The shoe insert 100
configured to control excessive bending in the toe region to help
prevent turf toe can have a flexural moduli with a ratio in the
range of approximately 1.25:1 to 2.5:1. In another embodiment the
ratio can be in the range of approximately 2:1 to 3:1, 2.5:1 to
4:1, 3:1 to 6:1, 5:1 to 10:1, 6:1 to 13:1, or 10:1 to 20:1.
Components of the shoe insert 100 coupled to the flex area 110 can
be made of a metal, polymer, composite, or combination thereof. In
general, the strengths and stiffness of fiber-reinforced composite
materials when used in the layers of the shoe insert 100 are
dependent on the properties of the type of fiber, the orientation
of the fiber, and the matrix used with the fiber. In one
embodiment, the material used in the layers of forming the dorsal
side 130 of the tunable rigid layer 112 is a carbon fiber epoxy
plate, and the material used in the plantar side 132 is either a
nitrile butadiene rubber, polyurethanes, or acrylics, or
thermoplastic polyurethane films or elastomeric films that are
joined to the surface of the flexible fiber substrate defining the
dorsal side 130. Other types of materials are possible; however,
the modulus of elasticity of the material used in the plantar side
132 must increase in modulus based on the angular rotation of the
metatarsal phalangeal joint 108. The material used in the dorsal
side 130 must also be higher in modulus than the plantar side 132
to minimize the bending of the arch of the foot and to provide the
flex area 110 of the shoe insert 100 with the necessary
anisotropically-flexible properties.
In one embodiment, to construct the shoe insert 100, base carbon
fiber fabric is first impregnated with elastomeric binders. The
impregnated carbon fiber fabric is then dried until the solvents
are removed. Drying time depends upon the solvent ratio and drying
temperature. The content of the impregnating elastomeric binders
can range from 0.5-50%, but preferably falls within the range of
5-23%, which is dependent upon the modulus ratio desired. No binder
can exhibit similar behavior. FIG. 18 is a diagram showing the
layered construction of a non-rigid flexible carbon fiber composite
136. An impregnated carbon fiber fabric 138 in one embodiment is
pressed at 325.degree. F. at 6 psi for 10 minutes between two
sheets 0.004 inch thick films, top 140a and bottom 140b. This
process produces a non-rigid flexible carbon fiber composite
136.
FIG. 19 is a diagram showing the layered construction of a
composite laminate 142. Each carbon fiber composite laminate 142 is
comprised of two or more layers of the non-rigid flexible carbon
fiber composites 136 joined to one or more rigid carbon fiber
plates or other rigid substrates. In one embodiment, on the dorsal
layer 104 of the shoe insert 100, a 0.093 inch thick polycarbonate
layer 144 is heat pressed to two sheets of the non-rigid carbon
fiber composite 136 at a temperature of 300.degree. F. at 6 psi for
10 minutes. On the plantar layer 106 of the shoe insert 100, the
two sheets of the non-rigid carbon fiber composite 136 are heat
pressed to two pieces of 0.030 inch thick rigid carbon fiber plates
146, or other rigid substrates, such as metal or plastic, at a
temperature of 300.degree. F. at 6 psi for 10 minutes. The rigid
carbon fiber plates 146 are spaced 1.25-1.5'' apart to form a gap
that serves as the flex area 110. The newly-formed laminate carbon
fiber epoxy plate is allowed to cool to 180.degree. F. before
removal from the press.
The coefficient of thermal expansion of polycarbonate at
300.degree. F. provides enough shrinkage upon cooling to create a
curved column. Non-rigid carbon fiber composites 136 are limited by
their compression strength and under compressive loading can form
curved columns, which are small bends in the material. FIG. 20 is a
diagram showing, by way of example, column bending in a non-rigid
carbon fiber composite 136. When the composite material is flexed
away from the neutral orientation, thereby putting the non-rigid
carbon fibers of the woven carbon fiber fabric 138 into tension,
curved columns begin to straighten until a point of straightness at
which point the material rapidly increases the maximum tensile
loading. This characteristic enables the carbon fiber composite
material 136 to be pre-stressed through the curved columns, such
that flexing of the material beyond a predetermined angle can be
limited or precluded, while preserving pliability before reaching
the predetermined angle. The curved columns are formed in the
non-rigid carbon fiber composite 136 at a predetermined angle that
sets the level of curvature in the curved column; when the
non-rigid carbon fiber composite 136 is flexed away from the
neutral orientation and the curved columns are placed in tension,
the flexural modulus significantly increases, thus enabling the
non-rigid carbon fiber composite 136 to fixedly engage or "lock
out" further flexion. As the non-rigid carbon fiber composite 136
combines one or more sheets of the non-rigid flexible carbon fiber,
breaking or failure of the composite material is precluded, as the
degrees to which curved columns are formed will differ as between
the individual sheets of the non-rigid flexible carbon fiber with
the result that the curved beams of the different sheets tolerate
compression, up to the predetermined angle.
The control of temperature and the use of various substrates
exhibiting different levels of coefficients of expansion can
produce varying amounts of contraction upon cooling to create a
desired amount of curvature. The curvature in the column allows the
polycarbonate substrate, or other lower modulus flexible materials,
to provide the bending stiffness desired and the subsequent
straightening of the curved column material imparts a strain
stiffening behavior of the resultant flexible composite
material.
In a further embodiment, to construct the shoe insert 100, the base
carbon fiber fabric 138 is first impregnated with elastomeric
binders. The impregnated carbon fiber fabric 138 is then dried
until the solvents are removed. Drying time depends upon the
solvent ratio and drying temperature. The content of the
impregnating elastomeric binders can range from 0.5-50%, but
preferably falls within the range of 5-23%, which is dependent upon
the modulus ratio desired. This material has substantially the same
form of layered construction as the non-rigid flexible carbon fiber
composite 136 described supra with reference to FIG. 18. The
impregnated carbon fiber fabric is pressed at 325.degree. F. at 6
psi for 10 minutes between two sheets 0.004 inch thick films, top
and bottom. This process produces a non-rigid flexible carbon fiber
composite.
Each assembly is a laminate stack that is composed of two or more
sheets of the non-rigid flexible carbon fiber composites and
titanium alloy or other rigid substrates. FIG. 21 is a diagram
showing the layered construction of the laminate stack 150. In one
embodiment, on the plantar layer 106 of the shoe insert 100, two
sheets of the non-rigid carbon fiber composite 136 are heat pressed
to a 0.043 inch thick polycarbonate layer 151 at a temperature of
300.degree. F. at 6 psi for 10 minutes. The pressed laminate stack
150 is then laid onto a 0.012 inch thick titanium alloy 152 and a
0.020 inch polycarbonate 153 is adhered using a 0.004 inch thick
thermoplastic polyurethane film. The combined laminate stack 150 is
hot pressed at a temperature of 300.degree. F. at 6 psi for 10
minutes and allowed to cool to 180.degree. F. before removal from
the press.
Next, the laminate stack 150 is heat formed to an angle of about
56.degree. about a 1.5 inch radius in the desired flex area. Note
that an angle of about 56.degree. is applicable to a shoe insert
that helps to prevent "turf toe." Different angles may be
appropriate to other applications, such as an elbow brace that
limits movement during rehabilitation following surgery. The
non-rigid carbon fiber fabric 136 is convex to the laminate stack
150. The laminate stack 150 is heat formed though localized heating
to form the 1.25 inch to 1.5 inch flex area over the radius using
an infrared heating source, a conductive heating block, or directed
hot air. The heat forming stretches the flexible carbon fiber
fabric's sheets based on their distance from the axis of flex. FIG.
22 is a diagram showing the change in length of each layer 155,
156, 157 in the laminate stack 150 as the radius 158 changes from
the original natural axis. The length of each successive layer
moving inward towards the axis of flex is shorter than the
preceding layer. After the laminate stack 150 is heat formed, the
laminate stack 150 is restored to a substantially flat form and the
layers 155, 156, 157 in the area of heat forming 160 are placed
under compression to form curved columns within the flex area.
In a still further embodiment, to construct the shoe insert 100,
base carbon fiber fabric is first impregnated with elastomeric
binders. The impregnated carbon fiber fabric is then dried until
the solvents are removed. Drying time depends upon the solvent
ratio and drying temperature. The content of the impregnating
elastomeric binders can range from 0.5-50%, but preferably falls
within the range of 5-23%, which is dependent upon the modulus
ratio desired. This material has substantially the same form of
layered construction as the non-rigid flexible carbon fiber
composite 136 described supra with reference to FIG. 18. The
impregnated carbon fiber fabric is pressed at 325.degree. F. at 6
psi for 10 minutes between two layers 0.004 inch thick films, top
and bottom. This process produces the flexible non-rigid carbon
fiber composite 136.
Each assembly is composed of one or more layers of the non-rigid
flexible carbon fiber composites 136 and a rigid substrate of
polycarbonate or titanium, or a rigid composite plate. FIG. 23 is a
diagram showing the layered construction of a carbon fiber joined
plate 164. In one embodiment, on the plantar layer 106 of the
insert 100, two layers of the non-rigid carbon fiber fabric 138 are
placed on top of a 0.020 inch thick rigid substrate 164 of
polycarbonate or titanium, or a rigid composite plate. The layered
pieces are then placed between two sheets of release paper and heat
formed. FIG. 24 is a diagram showing a heat forming tool 166 for
use with the carbon fiber joined plate 164 of FIG. 23. The layered
pieces placed into the heat forming tool 166, which is then heated.
The apex of the curve 168 in the center of the flex area 110 (FIG.
17) of the sole is formed into the base of the tool 166. The
layered pieces are heat pressed at a temperature of 300.degree. F.
at 6 psi for 10 minutes, and then cooled to 180.degree. F. before
removal from the press.
In a yet further embodiment, a layer of unidirectional fiber tape
is impregnated with elastomeric binders and joined to a rigid
substrate of polycarbonate or titanium, or a rigid composite plate,
such as described with reference to FIG. 23. The joined
unidirectional fiber tape is then placed between two layers of the
non-rigid carbon fiber composite 136 and heat formed though
localized heating or shaped using a heat forming tool 166, which
stretch the fiber layers to create curved columns.
Metals or plastics such as titanium and polycarbonate can be
stamped or molded with shapes, slits, and perforations. Shapes can
include but are not limited to pre-shaped buckles and bumps. Slits
can be straight or curved in a staggered or array pattern.
Perforations can be circles, ellipses, rectangles or squares.
The two components of the shoe insert 100 are joined together to
form a joined beam through laminating temperatures ranging from
200.degree. F. to 375.degree. F. for about ten minutes or less and
a pressure ranging from 2 psi to 8 psi, but is dependent upon the
material melting point and its ability to flow. The resulting
joined beam exhibits an increase in modulus based on angular
rotation of the metatarsal phalangeal joint 108 in the flex area
110 (FIG. 14). The increase in modulus exponentially increases in
high bending stiffness (moduli) until about an angle of 56.degree.,
after which a rapid rise in stiffness or a locking of the materials
prevent the flex area 110 from bending any further, thereby
protecting the metatarsal phalangeal joint 108 (FIG. 15) from
hyperextension.
Different configurations and combinations of fiber, such as carbon,
glass, Kevlar, composite materials, metal foils, and plastic sheets
can be advantageously used in the tunable rigid sheets 112 to
construct the anisotropically-flexible area 110. The flex
experienced by footwear when combined with a shoe insert 100 can be
empirically measured using a dynamic flexion shoe flexion device,
such as the Shoe Flexer product, manufactured by Exeter-Research,
Inc., Brentwood, N.H., which dynamically flexes each shoe while
measuring the torque required to flex about the flex area 110. A
three-point bend on such an anisotropically-flexible shoe insert
100 at the flex area 110 can be used to measure torque (moments) at
angles below 25.degree. quasi-statically for low torque angle
measurements. FIG. 25 is a graph 170 showing, by way of example,
the differences between flexural moduli in exemplary testing
configurations. The x-axes represent flex angle in degrees. The
y-axes represent torque in Nm. The empirical testing was conducted
using a shoe equipped with an anisotropically-flexible shoe insert
100 at the flex area 110 that achieved dynamic testing results not
reached in traditional football cleat construction with 60 Nm at
60.degree. of flex angle. Conventional football cleat technology
has torque values of 16-18 Nm at 75.degree. of flex angle. The
dynamic flex tester flexes the shoe at a rate of 600-800 degrees
per second. The flex test data demonstrates control of increasing
torque at controlled flex angles based on construction and
materials in the flex area 110.
The range of motion stiffness can be tuned through variation in
moduli combinations and laminate construction. The moduli can be
changed based on resin matrix modulus, fabric weave pattern, and
fiber orientation. FIGS. 26A and 26B are illustrations showing, by
way of examples, controlled curvature in columns in a non-rigid
carbon fiber material 172, 174 under pre-compression through
thermally controlled contraction, by pre-forming to a predetermined
engagement angle and by segmented wedges (or partial cuts or
cut-through designs) with combined angles achieving 56.degree. flex
angle and fully engaging the non-rigid carbon fiber at a
predetermined lock-out angle. The segmented wedges, partial cuts or
cut-through designs are formed into the shoe insert 100 such that
the modulus of elasticity remains low until the segmented wedges,
partial cuts or cut-through designs compress into a substantially
solid structure after which the modulus of elasticity increases. By
changing the matrix modulus, the buckling resistance will change,
therefore changing the engagement point of the material. The matrix
modulus can vary between less than 50 psi to greater than 300,000
psi.
The engagement point is variable, based on the level of contraction
or preformed angle. The amount of curvature in the column at each
level can be adjusted by varying the number of sheets of fibers and
controlling whether the fibers are unidirectional or weaved. For
example, a two-layer non-rigid carbon fiber material that has been
joined to a high modulus substrate will have an inner layer of
carbon fiber material joined against the high modulus substrate
with a lower level of curvature in the column and an outer layer of
carbon fiber material with higher amounts of curvature in the
column that engage at different angles of rotation. The combination
provides a varying modulus of elasticity as the fibers become more
and more engaged under strain.
The engagement point also changes based on the weave density. Weave
densities affect weave crimp by changing the spacing of the
transverse tows, thereby changing the column length for buckling
during thermal or preformed curvature control. For example, a 268
gsm fabric will have approximately 16 tows per inch, which yields a
tow spacing of 0.0625 inches and with a 2.times.2 twill pattern
gives a 0.125 inch column length. A 200 gsm fabric will be 12.5
tows per inch, which yields a tow spacing of 0.080 inches and with
a 2.times.2 twill pattern gives a 0.160 column length. Shorter
column lengths decrease the amount of flex angle engagement while
longer column lengths increase the amount of flex angle engagement.
Other suitable weave pattern, densities and fiber weights are
possible. For example, tow or fiber bundle diameters may vary based
on the number of filaments in the bundle, and common carbon fiber
bundle sizes have a range of 1,000 to 50,000 filament fibers.
Referring back to FIG. 25, the torque should target below 10-12 Nm
in athletic footwear at up to 25.degree. of flex. The lower the
value becomes, the more freely the metatarsal phalangeal joint is
able to rotate, which minimizes fatigue. The torque value should
increase up to 30 Nm at up to 56.degree. of flex, and beyond
56.degree. of flex, the torque value should meet or exceed 60 Nm at
up to 75.degree. of flex. FIG. 25 also shows a comparison of
different constructions of the flex test with plate construction
only without the shoe being tested and in static test versus the
shoe test being tested in dynamic. The values of the plates can be
controlled through all zones with increasing of stiffness through
the active zone and with a rapid increase in stiffness beyond
60.degree. of flex. Shifting the fabric can increase the modulus in
tension as the fibers orient during strain, which decreases the
fiber angle and aligns with the load to increase in strength.
In a further embodiment, an anisotropically-flexible beam can be
constructed as a weave pattern and unidirectional fibers that
provide differing moduli based on weave direction and fiber
orientation. This material changes layer orientations of the
non-rigid material to provide strain-stiffening behavior as
discussed above.
While the invention has been particularly shown and described as
referenced to the embodiments thereof, those skilled in the art
will understand that the foregoing and other changes in form and
detail may be made therein without departing from the spirit and
scope of the invention.
Remarks
The above description and drawings are illustrative and are not to
be construed as limiting. Numerous specific details are described
to provide a thorough understanding of the disclosure. However, in
some instances, well-known details are not described in order to
avoid obscuring the description. Further, various modifications may
be made without deviating from the scope of the embodiments.
Reference in this specification to "one embodiment" or "an
embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment of the disclosure. The
appearances of the phrase "in one embodiment" in various places in
the specification are not necessarily all referring to the same
embodiment, nor are separate or alternative embodiments mutually
exclusive of other embodiments. Moreover, various features are
described which may be exhibited by some embodiments and not by
others. Similarly, various requirements are described which may be
requirements for some embodiments but not for other
embodiments.
The terms used in this specification generally have their ordinary
meanings in the art, within the context of the disclosure, and in
the specific context where each term is used. It will be
appreciated that the same thing can be said in more than one way.
Consequently, alternative language and synonyms may be used for any
one or more of the terms discussed herein, and any special
significance is not to be placed upon whether or not a term is
elaborated or discussed herein. Synonyms for some terms are
provided. A recital of one or more synonyms does not exclude the
use of other synonyms. The use of examples anywhere in this
specification, including examples of any term discussed herein, is
illustrative only and is not intended to further limit the scope
and meaning of the disclosure or of any exemplified term. Likewise,
the disclosure is not limited to various embodiments given in this
specification. Unless otherwise defined, all technical and
scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure pertains. In the case of conflict, the present document,
including definitions, will control.
* * * * *
References