U.S. patent application number 16/788151 was filed with the patent office on 2020-06-11 for fiber-reinforced composite material.
The applicant listed for this patent is Howard E. Crawford, III. Invention is credited to Howard E. Crawford, III.
Application Number | 20200180260 16/788151 |
Document ID | / |
Family ID | 55808843 |
Filed Date | 2020-06-11 |
![](/patent/app/20200180260/US20200180260A1-20200611-D00000.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00001.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00002.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00003.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00004.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00005.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00006.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00007.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00008.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00009.png)
![](/patent/app/20200180260/US20200180260A1-20200611-D00010.png)
View All Diagrams
United States Patent
Application |
20200180260 |
Kind Code |
A1 |
Crawford, III; Howard E. |
June 11, 2020 |
FIBER-REINFORCED COMPOSITE MATERIAL
Abstract
Briefly, a variety of embodiments of composite materials
including part fabrication using composite materials is
described.
Inventors: |
Crawford, III; Howard E.;
(Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Crawford, III; Howard E. |
Beijing |
|
CN |
|
|
Family ID: |
55808843 |
Appl. No.: |
16/788151 |
Filed: |
February 11, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14685407 |
Apr 13, 2015 |
10596778 |
|
|
16788151 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2262/101 20130101;
B29C 2793/0081 20130101; B32B 27/04 20130101; B32B 5/28 20130101;
B32B 2260/046 20130101; B32B 2260/023 20130101; Y10T 428/24314
20150115; B32B 27/06 20130101; B32B 2262/0269 20130101; B29C 41/50
20130101; B32B 2262/106 20130101; B32B 5/02 20130101; B29B 15/08
20130101; B32B 3/266 20130101; B26D 3/006 20130101; B32B 5/12
20130101 |
International
Class: |
B32B 3/26 20060101
B32B003/26; B29C 41/50 20060101 B29C041/50; B26D 3/00 20060101
B26D003/00; B32B 27/06 20060101 B32B027/06; B32B 27/04 20060101
B32B027/04; B32B 5/12 20060101 B32B005/12; B32B 5/02 20060101
B32B005/02; B32B 5/28 20060101 B32B005/28 |
Claims
1.-28. (canceled)
29. A method of forming a composite part comprising: heating a
discontinuous fiber reinforced composite panel to a temperature so
that the panel becomes pliable; forming the heated panel in a
manner so that it stretches to substantially conform to a mold
having a shape that includes compound curves; and cooling the
shaped panel.
30. The method of claim 29, wherein the forming includes: pressure
forming the panel onto the mold via compression molding the heated
panel with a compression tool that includes the mold in which the
compression tool is closed so that the panel is pressed to a mold
surface of the compression tool.
31. The method of claim 29, wherein the forming the heated panel
includes stretching the panel in a manner so that nearly all
discontinuous fibers in the panel are in physical contact with or
physically overlap with another discontinuous fiber before
stretching and remain in physical contact with or continue to
physically overlap with the another discontinuous fiber after
stretching.
32. The method of claim 29, wherein the dimensions of the part are
in the range of from about 0.02 square meters to about 4 square
meters.
33.-38. (canceled)
39. The method of claim 31, wherein the forming comprises vacuum
forming in which a vacuum is initiated to remove air between the
mold and the panel to permit the pliable panel to more tightly
substantially conform to the shape provided by the mold.
40. The method of claim 29, wherein the discontinuous fiber
reinforced composite panel comprises at least two sheets with
respective sheets comprising a composite of a matrix material and a
reinforcement material.
41. The method of claim 40, wherein the matrix material comprises
one or more polymer materials and the reinforcement material
comprises one or more fiber materials.
42. The method of claim 41, wherein the one or more polymer
materials comprises at least a thermoplastic and/or a thermoset
polymer material.
43. The method of claim 42, wherein the discontinuous fiber
reinforced composite panel comprises a pair of mutually and
immediately adjacent respective sheets in direct physical
contact.
44. The method of claim 42, wherein the discontinuous fibers in the
respective sheets of the discontinuous fiber reinforced composite
panel result from a respective pattern of slits in the respective
sheets.
45. The method of claim 43, wherein the pattern of slits in a
respective sheet are offset aligned from the pattern of slits in an
immediately adjacent sheet in a manner so that during the forming,
that includes stretching the sheets, most, if not all, openings
created at slit locations in the respective sheet are bridged
during the forming by substantially parallel discontinuous
reinforcing fibers of the immediately adjacent sheet.
46. The method of claim 42, wherein the forming comprises a forming
process in a manner so that nearly all discontinuous fibers in the
panel in contact with or that physically overlap with another
discontinuous fiber of an adjacent sheet remain in contact with or
continue to physically overlap with the another discontinuous fiber
of an adjacent sheet via limiting and/or controlling the stretching
resulting from the forming process.
47. The method of claim 46, wherein the forming comprises vacuum
forming and wherein the vacuum forming uses conventional vacuum
forming equipment.
48. The method of claim 47, wherein the vacuum forming equipment
includes the capability to heat different sections of the
discontinuous fiber reinforced composite panel to different
temperatures substantially in accordance with programming included
as a component of the vacuum forming equipment.
49. A method of cutting a pattern of slits in a uni-directional
fiber reinforced polymer sheet comprising: placing the
uni-directional fiber reinforced polymer sheet on a cutting bed
using tension guides; and cutting the pattern of slits in the
uni-directional fiber reinforced polymer sheet while the
uni-directional fiber reinforced polymer sheet is over the cutting
bed between the tension guides.
50. The method of claim 49, wherein the uni-directional fiber
reinforced polymer sheet is fed over the cutting bed in a manner so
that the uni-directional fiber reinforced polymer sheet unwinds
from one spool prior to being cut with the pattern of slits and
rewinds onto another spool after being cut with the pattern of
slits.
51. The method of claim 50, wherein the uni-directional fiber
reinforced polymer sheet is fed through the tension guides via
mechanical pulling.
52. The method of claim 49, wherein the cutting the pattern of
slits comprises cutting the pattern of slits with a laser or with a
rotary blade.
53. The method of claim 52, and further comprising: programming the
laser or the rotary blade in advance to cut the pattern of slits.
Description
BACKGROUND
1. Field
[0001] This disclosure relates to composite material and/or
fabricating parts from composite materials.
2. Information
[0002] In a variety of industries, parts are fabricated using
composite materials. However, doing so may involve a variety of
trade-offs. For example, fabrication using composite materials of
adequate strength for some uses, such as for complex parts, may be
challenging without significant amounts of labor, which may add
cost, and/or may simply not be feasible.
BRIEF DESCRIPTION OF DRAWINGS
[0003] Claimed subject matter is particularly pointed out and
distinctly claimed in the concluding portion of the specification.
However, both as to organization and/or method of operation,
together with objects, features, and/or advantages thereof, it may
best be understood by reference to the following detailed
description if read with the accompanying drawings in which:
[0004] FIG. 1 is an illustration, shown in plan view, of an
embodiment of a sheet of continuous fiber reinforced composite
material;
[0005] FIG. 2 is an illustration, shown in plan view, of two
respective embodiments of a sheet of discontinuous fiber reinforced
composite material in plan view;
[0006] FIG. 3 is an illustration, shown in isometric view, of the
embodiments of FIG. 2 used to form an embodiment of a panel of
composite sheets;
[0007] FIG. 4 is an illustration, shown in plan view, of the
embodiment of a panel of FIG. 3;
[0008] FIG. 5 is a plan view a discontinuous fiber reinforced
sheet, such those shown in FIG. 2.
[0009] FIG. 6 is a detailed view of a section of FIG. 5;
[0010] FIG. 7 is an illustration, shown in isometric view, of
another embodiment of a panel of composite sheets;
[0011] FIGS. 8-11 are a side view of a panel looking from plane A
as shown in FIG. 19.
[0012] FIGS. 12-15 illustrates slit angle, slit length, distance or
separation between slits, overlap of immediately adjacent
neighboring columns of slits for an embodiment of a discontinuous
fiber reinforced polymer sheet;
[0013] FIG. 16 is an illustration of an embodiment for fabricating
an embodiment of a continuous fiber reinforced polymer sheet;
[0014] FIG. 17 is an illustration of an embodiment for fabricating
an embodiment of a panel of composite sheets;
[0015] FIG. 18 is an illustration of an embodiment of a machine for
use in thermoforming;
[0016] FIG. 19 is an illustration of an embodiment of a panel of
composite sheets in which a plane dissects the panel along two
substantially coincident fibers of the composite sheets; and
[0017] FIG. 20 is an illustration of another embodiment of a panel
of composite sheets.
[0018] Reference is made in the following detailed description to
accompanying drawings, which form a part hereof, wherein like
numerals may designate like parts throughout to indicate
corresponding and/or analogous components. It will be appreciated
that components illustrated in the figures have not necessarily
been drawn to scale, such as for simplicity and/or clarity of
illustration. For example, dimensions of some components may be
exaggerated relative to other components. Further, it is to be
understood that other embodiments may be utilized. Furthermore,
structural and/or other changes may be made without departing from
claimed subject matter. It should also be noted that directions
and/or references, for example, such as up, down, top, bottom, and
so on, may be used to facilitate discussion of drawings and/or are
not intended to restrict application of claimed subject matter.
Therefore, the following detailed description is not to be taken to
limit claimed subject matter and/or equivalents.
DETAILED DESCRIPTION
[0019] References throughout this specification to one
implementation, an implementation, one embodiment, an embodiment
and/or the like means that a particular feature, structure, and/or
characteristic described in connection with a particular
implementation and/or embodiment is included in at least one
implementation and/or embodiment of claimed subject matter. Thus,
appearances of such phrases, for example, in various places
throughout this specification are not necessarily intended to refer
to the same implementation and/or embodiment or to any one
particular implementation and/or embodiment described. Furthermore,
it is to be understood that particular features, structures, and/or
characteristics described are capable of being combined in various
ways in one or more implementations and/or embodiments and,
therefore, are within intended claim scope, for example. In
general, of course, these and other issues vary with context.
Therefore, particular context of description and/or usage provides
helpful guidance regarding inferences to be drawn.
[0020] Likewise, in this context, the term contact or physical
contact is used generically to indicate that two or more
components, such as sheets, for example, are in direct physical
contact or are in indirect physical contact. Indirect physical
contact refers to physical contact that includes a physical
intermediary, for example, in an appropriate context. Thus, as an
example, two sheets may be in physical contact in this context,
albeit indirect physical contact, in a situation in which a third
sheet is between the two sheets, so that one of the two sheets is
in direct physical contact with one side of the third sheet and the
other of the two sheets is in direct physical contact with the
other side of the third sheet.
[0021] The terms, "and", "or", "and/or" and/or similar terms, as
used herein, include a variety of meanings that also are expected
to depend at least in part upon the particular context in which
such terms are used. Typically, "or" if used to associate a list,
such as A, B or C, is intended to mean A, B, and C, here used in
the inclusive sense, as well as A, B or C, here used in the
exclusive sense. In addition, the term "one or more" and/or similar
terms is used to describe any feature, structure, and/or
characteristic in the singular and/or is also used to describe a
plurality and/or some other combination of features, structures
and/or characteristics. Likewise, the term "based on" and/or
similar terms are understood as not necessarily intending to convey
an exclusive set of factors, but to allow for existence of
additional factors not necessarily expressly described. Of course,
for all of the foregoing, particular context of description and/or
usage provides helpful guidance regarding inferences to be drawn.
It should be noted that the following description merely provides
one or more illustrative examples and claimed subject matter is not
limited to these one or more illustrative examples; however, again,
particular context of description and/or usage provides helpful
guidance regarding inferences to be drawn.
[0022] The term composite in this context refers to a material made
from more than one constituent material. Typically, there are at
least two types of constituent materials: a matrix-type material
and a reinforcement-type material. Thus, in this context, the term
composite, such as with reference to a composite material, refers
to a material employing constituents with at least a portion of
these previously mentioned respective types.
[0023] Typically, one or more matrix materials surround and/or
support one or more reinforcement materials, such as by maintaining
relative positions at least to a degree. One or more reinforcement
materials typically provide mechanical and/or physical properties.
A combination of matrix and reinforcement materials typically
produces a material having a set of desired properties unavailable
from the constituents individually.
[0024] Fabrication of a part usually includes imparting a shape to
the part to be fabricated. A matrix material, for example,
typically experiences a melding event, after which part shape may
be largely set. A melding event may occur in various ways, such as
by chemical polymerization and/or solidification from a melted
state. Likewise, a matrix material may be introduced to a
reinforcement material before or after the reinforcement material
is placed into a cavity or onto a surface, for example, during
fabrication.
[0025] A variety of methods is available for fabrication and may
vary depending at least in part on end-product objectives. Thus, a
variety of factors may be considered. As an illustrative and a
non-limiting example, properties of one or more matrix and/or one
or more reinforcement materials in combination and/or individually
typically may be included among a variety of factors to be
considered. Likewise, gross quantity of parts to be produced may be
included among a variety of factors to be considered in some cases,
which may, likewise, at least partially affect cost. Thus, cost may
be included among a variety of factors to be considered.
[0026] Often composites use a polymer matrix material. There are
many different polymers available. More commonly employed polymers
include polyester, vinyl ester, epoxy, phenolic, polyimide,
polyamide, polypropylene, PEEK, combinations thereof and/or others.
A reinforcement material may comprise a fiber, although others are
known as well, as discussed more below. Types of polymer commonly
used respectively comprise thermosets, thermoplastics, and/or
combinations thereof. Examples of thermosets respectively include
unsaturated polyesters, vinylesters, epoxies, phenolics,
polyurethanes, and/or combinations thereof.
[0027] Thermosets (also referred to as thermoset resins) employ a
curing agent. Thus, as an illustration, impregnation with respect
to a reinforcing material, followed by curing, may be employed to
fabricate a part using a thermoset. Curing thus typically sets
shape of the part if employing a thermoset matrix material. In
general, epoxies are commonly used in industry. Typically these are
relatively high-viscosity liquids. A curing agent is employed to
affect reaction rate and may also affect performance
characteristics of a part being fabricated. Some more commonly used
curing agents comprise: methyl ethyl ketone peroxide (MEKP),
methylene-dianiline (MDA) or, sulfonyldianiline (DDS). MEKP, for
example, is commonly used for polyester or vinylester.
[0028] Thermoplastic refers to a polymer material that becomes
pliable or moldable above a specific temperature and solidifies as
a result of cooling. Thermoplastics typically have a high molecular
weight. Polymer chains associate through intermolecular forces,
which weaken rapidly with increased temperature and/or pressure,
yielding a viscous liquid. Thus, thermoplastics may be reshaped
using heat and/or pressure and are typically used to produce parts
by injection molding and/or similar processes. Thermoplastics
differ from thermosetting polymers, which form irreversible
chemical bonds during a curing process.
[0029] Thus, thermoplastics are typically employed initially as
nonreactive solids (e.g., typically no chemical reaction occurs
during processing/fabrication). Heat and/or pressure may instead be
employed to form a part. Unlike thermosets, thermoplastics (also
referred to as thermoplastic resins) usually are able to be
reheated and reformed into another shape, if desired.
[0030] Thus, examples of possible matrix and/or reinforcement
materials, without intending to be exhaustive, include:
Thermoplastic Resins:
Polypropylene (PP)
Polyethylene (PE)
[0031] Polyethylene terephthalate (PET)
Polyamide 6 (Nylon 6)
Polyamide 66 (Nylon 66)
Rigid Thermoplastic Polyurethane (TPU)
Polycarbonate (PC)
[0032] Polycarbonate/Acrylonitrile butadiene styrene (PC/ABS)
PVDF--Polyvinylidene fluoride Polyphenylene sulfide (PPS) Polyether
ether ketone (PEEK)
Fibers:
Glass (E-glass)
Glass (S-Glass)
[0033] Carbon/Graphite (standard modulus) Carbon/Graphite
(intermediate modulus) Carbon/Graphite (ultra-high modulus) Aramid
(high toughness) Aramid (high modulus) Aramid (ultra-high
modulus)
Basalt
Bamboo
Wood
[0034] Referring to FIG. 15, as an example, to produce a composite
material, fiber roving 420, such as E-glass 420, may be passed
through an impregnation die 430. For example, fibers may be
introduced where they may be impregnated with thermoplastic resin.
For example, as fibers pass through impregnation die 430, they may
contact a thermoplastic melt 450 so that thermoplastic material is
able to combine with the fibers. Thus, an impregnation die, for
example, may provide a mechanism to "wet out" fiber reinforcement
material with thermoplastic material in an embodiment. As
fiber/thermoplastic material 490 exits die 430, it may be cooled,
and wound onto spools 480 via 470 and 490, for example.
[0035] A uni-directional, fiber reinforced thermoplastic sheet, for
example, may be produced in such as manner and may typically have a
thickness range of from about 0.16 mm to about 0.6 mm, as an
example. Thus, as one non-limiting illustration, a number of
continuous fiber reinforced sheets are made by this method and
range in thickness from about 0.15 mm to about 0.30 mm. A composite
sheet typically may be about 1000 mm wide, for example. However, as
shall be described below, a fiber reinforced thermoplastic sheet
may be replaced with a panel comprising two composite polymer
sheets, in an embodiment. Thus, for example, a sheet to be included
in panel may comprise a thinner sheet, such as, in an embodiment, a
composite polymer sheet, produced from a process similar to as
described above, having a thickness in the range of from about 0.08
mm to about 0.3 mm. An illustrative embodiment, as an example, may
employ a thickness in the range from about 0.09 mm to 0.25 mm, for
example, with a typical thickness of about 0.125 mm and an areal
weight of about 185 grams per square meter for roughly 60% glass
fiber by weight in a polypropylene thermoplastic matrix. Table 1
below provides common areal weights for uni-directional, fiber
reinforced thermoplastic sheets according to thermoplastic matrix
type.
TABLE-US-00001 TABLE 1 Uni-Directional, Fiber Reinforced
Thermoplastic Sheets Areal Weights Fiber Thickness Weight Matrix
Resin Reinforcement (mm) (grams/m.sup.2) PET Glass 0.125 239 PA6
Glass 0.125 213 PC/ABS Glass 0.125 213 Polypropylene Glass 0.125
185 HDPE Glass 0.125 174 PET Carbon 0.125 195 PA6 Carbon 0.125 181
PG/ABS Carbon 0.125 178 Polypropylene Carbon 0.125 139
Composite material may be wound onto rolls for convenience with
respect to further manufacturing to be performed. Of course,
claimed subject matter is not intended to be limited to
illustrative examples, such as the foregoing.
[0036] Without intending to be exhaustive, other methods are also
available to manufacture composite sheets, such as using high
pressure laminates. For example, thermoplastic films may be placed
on either side of a fiber reinforcement material. The combination
may be subjected to heat and/or pressure to produce melting of the
matrix material onto and through the fiber reinforcement material.
In yet another example method, co-mingled fiber/thermoplastic
rovings may be heated, spread, cooled and wound onto a spool. Thus,
as suggested, a variety of approaches are possible and claimed
subject matter is not intended to be limited to a particular
approach or method.
[0037] In an illustrative embodiment, claimed subject matter, for
example, may comprise a fiber reinforced polymer composite panel to
be used in standard vacuum forming equipment to produce three
dimensional composite parts with material properties approaching
those of a part made from a polymer composite panel constructed
from multiple uni-directional, continuous fiber reinforced polymer
composite sheets. Thus, in an illustrative, but non-limiting
embodiment, a panel may comprise at least two sheets of
uni-directional fiber reinforced polymer sheets in which the fiber
comprises continuous fiber but for a pattern of slits made in the
polymer sheets to slice the fiber into discontinuous fiber strands.
For example, uni-directional, fiber reinforced polymer (e.g.,
thermoplastic) composite sheets, such as example embodiment 1510,
as shown in a plan lay out in FIG. 1, may be supplied by companies
such as: Polystrand, Inc., (at Englewood, Colo.), Koninklijke Ten
Cate nv (TenCate), (at Almelo, The Netherlands), Celanese
Corporation (at Irving, Tex.), and Lanxess Corporation (at
Pittsburgh, Pa.).
[0038] For an example embodiment in which a panel comprises a pair
of sheets, a thickness between about 0.05 mm and about 0.5 mm, for
example, may provide desirable results. For example, a thickness of
about 0.25 mm may be used for an embodiment of a panel comprising
two sheets of thickness 0.125 mm. However, it is, again, noted that
claimed subject matter is not intended to be limited to
illustrative examples, such as the foregoing. However, continuing
with an illustrative embodiment, at least two polymer sheets, such
as 1610 and 1620, having uni-directional fibers in which the
respective sheets have a pattern of slits, as shown in FIG. 2, may
be placed mutually adjacent, as shown further in FIG. 3. Slits may
be made to slice continuous fibers of respective sheets into
discontinuous fiber strands, as shall be described. Furthermore, as
illustrated in FIG. 3, by sheets 1710 and 1720 being mutually
adjacent, for an example embodiment, a panel 1730 may be
formed.
[0039] In an embodiment, as shown by FIG. 4, with panel embodiment
1810, a substantially similar slit pattern may be employed for
sheets that are mutually and immediately adjacent (e.g., forming a
sheet pair). For example, in an embodiment in which adjacent sheets
are substantially the same size, if adjacent sheets are arranged to
have substantially coincident edges, then a slit pattern may be
substantially the same but for an offset substantially along the
direction of the fibers (e.g., a vertical offset) so that slit
locations are not perfectly aligned for mutually adjacent,
physically contacting sheets in a pair, again, shown by 1810, also
shown in more detail, and discussed in more detail below. For
example, vertical offset 1805, which corresponds to vertical offset
1605 for 1620 of FIG. 2, shows an amount of vertical translation of
a pattern of slits on sheet 1610 so as to form a substantially
similar slit pattern on sheet 1620. As an illustrative example, a
vertical offset may be in the range from about 10 mm to about 40
mm. However, separation or distance between slits for an adjacent
sheet of a panel may be a factor. Thus, for example, for an
illustrative embodiment, a range of from about 25% to about 75% of
the slit separation of an adjacent panel sheet may be employed.
[0040] Thus, in an example embodiment, for a panel,
discontinuous-fiber-reinforced polymer sheets may be in physical
contact, for example. A first polymer sheet of two sheets of a
pair, for example may comprise substantially parallel fibers
embedded in the sheet, the fibers being oriented in a direction
substantially parallel to sheet vertical edges. Fibers, again, may
be otherwise continuous but for a pattern of slits that result in
discontinuous strands of embedded fibers.
[0041] For example, FIG. 5 illustrates a pattern of slits for an
example embodiment sheet 110. A pattern of slits may, for example,
comprise adjacent vertical columns of slits, the columns extending
from one vertical edge of a polymer sheet to the other vertical
edge of a polymer sheet, as shown in FIG. 5.
[0042] Likewise, slits of any particular column, such as slits 130,
for example, may be mutually substantially aligned within the
particular column. Likewise, any particular column of slits may
overlap to a limited extent with any immediately adjacent
neighboring column of slits, which may be seen more easily in the
details of FIG. 6 by slits 220 and 230, for example (and discussed
below in more detail). Although claimed subject matter is not
restricted to a particular scale, FIG. 5 illustrates sheet 110 as
being 15.00 inches horizontally across, whereas FIG. 6 illustrates
the lower left corner of 110 in greater detail and depicts a 1.00
by 1.00 inch square area sub-portion.
[0043] Of course, a variety of patterns of slits are possible. It
is not intended to limit claimed subject matter to embodiments
provided for illustration, such as FIG. 5, as an example. As an
example, slits in an immediately adjacent, neighboring column may
be inclined at virtually any angle. Thus, for example, an
immediately adjacent, neighboring column does not necessarily need
to comprise a supplementary angle, although FIG. 5 illustrates an
embodiment employing supplementary angles, described in more detail
below.
[0044] However, an approach, such as the embodiment of FIG. 5, may
potentially provide a more uniform surface appearance and/or
potentially result in more uniform stretching during thermoforming.
But, as simply another illustrative example, an immediately
adjacent, neighboring column of slits could also comprise slits
having substantially the same slit angle, illustrated, for example,
in FIG. 20.
[0045] As mentioned, in an embodiment, an immediately adjacent,
neighboring column may employ slits at any angle. However,
typically, slits of a particular column may comprise substantially
aligned slits. As described in more detail below, also, typically,
an overlap between columns of slits is desirable so that continuous
fibers are sliced into discontinuous strands. Also typically, it
may be desirable for an adjacent sheet to be offset, also described
in more detail below.
[0046] Thus, continuing, similar to FIG. 5, as previously
described, for an embodiment, now referring to FIGS. 6 and 7, for
any two immediately adjacent neighboring columns, slits of one of
the two columns may be substantially oriented at an oblique angle
relative to a horizontal direction substantially perpendicular to
the direction of the fibers and slits of the other of the two
columns may be substantially oriented at an angle comprising a 180
degree supplement thereto (e.g., supplementary angles). For
example, in FIG. 6, slit 220 is substantially oriented at an
oblique angle relative to a horizontal, assuming a right hand
rotation rule (e.g., counter-clock wise). This angular orientation
is illustrated more clearly in FIG. 12, by slit angle 1140 for slit
1130.
[0047] Referring again to FIG. 6, if slit 220 is considered to be
in one of two immediately adjacent, neighboring columns, for
example, slit 250 may be considered to be in the other of two
immediately adjacent, neighboring columns. Slit 250, likewise, as
shown, is substantially oriented at an angle comprising a 180
degree supplement to the angle of slit 220 in an embodiment.
[0048] Furthermore, in an example embodiment, for any particular
column of substantially aligned slits, the substantially aligned
slits of the particular column may be consistently separated a
corresponding distance apart and the substantially aligned slits of
the column may have a correspondingly consistent length, also
illustrated by the sheet embodiment of FIG. 5. For example,
referring to FIG. 13, reference numeral 1310 points to a separation
or distance that would be correspondingly consistent between slits
in a column if more slits were illustrated (as shown in FIG. 5, for
example) and reference numeral 1320 points to a correspondingly
consistent slit length.
[0049] A pattern of slits may be formed in a polymer sheet of
uni-directional continuous fibers, such as described previously,
for example, so as to form discontinuous fiber strands embedded in
the polymer sheet having particular lengths and having fiber strand
endpoints particularly positioned related to endpoints of other
fiber strands. One example pattern, as previously suggested, is
shown in FIG. 5. However, as previously explained, FIG. 5 is a
non-limiting illustration. Thus, various slit features, such as
slit angle, distance (e.g. separation) between slits of a column
and/or slit length, as examples, may vary in different embodiments.
As one example, an oblique slit angle can vary from about 10
degrees to about 80 degrees. Typical ranges for an illustrative
embodiment might be, for example, from about 30 degrees to about 79
degrees. In an embodiment, as suggested previously, two polymer
sheets may be joined to comprise a sheet pair forming a panel. One
embodiment, for example, is illustrated in FIG. 4.
[0050] In an embodiment, for example, referring to FIG. 19, if a
plane A were to cut a panel along the direction of two
substantially coincident fibers (e.g., both laying substantially in
plane A), FIG. 8 illustrates a view looking into the cut panel from
the plane (with some slight exaggeration for emphasis). FIG. 8
shows an embodiment after slits have been made. For example,
reference numerals 770 and 730 point to breaks in respective fibers
corresponding to slits in respective sheets of the example panel.
Likewise, fiber strands 710 and 720 are portions of one otherwise
continuous fiber (corresponding to break 730) and fiber strands 740
and 760 are portions of another otherwise continuous fiber
(corresponding to break 770). Otherwise continuous, here, meaning
that the fibers would be continuous but for the presence of slits.
As suggested, in this illustrative example, the two otherwise
continuous fibers both lay in the plane cutting the panel of FIG.
19.
[0051] FIG. 9 illustrates a similar view as FIG. 8 with some
stretching as may occur from vacuum forming, for example. As shown,
breaks in FIG. 8 may potentially form wider gaps at respective slit
locations as a result of stretching. However, as also shown in an
example embodiment, fiber strands in a neighboring, immediately
adjacent sheet, are potentially able to bridge corresponding gaps
(e.g., openings). For example, fiber strand 860 potentially bridges
opening or gap 830. Likewise, fiber strand 810 potentially bridges
gap 870. As shown in FIG. 9, in an embodiment, fiber strands may be
formed in positions relative to slits of an adjacent sheet for a
panel so as to potentially distribute an applied load, for example,
to thereby at least facilitate maintaining or possibly even
increasing mechanical strength of a part to be fabricated. However,
as suggested by FIG. 10, it is desirable to not stretch a panel to
a point so that fiber strands potentially might not as effectively
distribute a load, such as if a sheet is stretched to a point that
a fiber strand of an adjacent sheet may not be sufficient to bridge
ends of two fiber strands, as shown for example in FIG. 10. For
example, fiber strand 910 is not long enough to bridge the ends of
fiber strands 940 and 950. Consistent with such an approach, in an
embodiment, stretching may, during vacuum forming, be such that an
overlap of at least about 5 mm, for example, remains, as
illustrated for example, by 1045 in FIG. 11.
[0052] A variety of slit patterns may be generated with potential
beneficial effect. One attribute mentioned previously for an
example embodiment relates to, for a pair of polymer sheets of a
panel, offset, but otherwise substantially aligned, slits in
respective polymer sheets, as shown, for example, by 1805 in FIGS.
4 and 1605 in FIG. 2. Furthermore, referring again to an example
embodiment, such as FIG. 5, in the example shown, slits of
immediately adjacent, neighboring columns of a particular polymer
sheet are arranged in a manner so that slits are not aligned
horizontally. This is illustrated in more detail, for example, in
FIG. 14, in which an end B of slit 1230 is positioned to be roughly
about half-way between respective ends C and D of slits 1240 and
1220, for example. Thus, in this example embodiment, slit 1230 is
positioned approximately near a center point between the least
remote ends of slits 1240 and 1220, respectively, of an immediately
adjacent neighboring column (other column slits shown in FIG. 5,
for example, have ends similarly positioned, as further examples).
A benefit of slits of immediately adjacent, neighboring columns not
being horizontally aligned is so that a "zigzag" of slits does not
horizontally cross a sheet. Thus, in an embodiment, sheets are more
easily handle-able in that the sheets do not fall apart.
[0053] Again, a variety of potential patterns may be available to
potentially facilitate distributing a load across fiber strands
embedded in a sheet or panel. Nonetheless, with such an
understanding, features of an example embodiment of a pattern of
slits are now described in detail for illustrative purposes. For
convenience, but without intending to limit claimed subject matter,
the following parameters may be employed to describe an example
embodiment: [0054] 1. slit length (e.g., reference numeral 1320 of
FIG. 13) may affect a capability of a fiber strand to move during
vacuum forming, for example, to allow a matrix material to
substantially conform to a tool surface by stretching; a slit
length less than 2 mm may not be desirable since this might affect
column overlap; slit length may comprise a reasonably wide range,
such as typically between from as short as below 15 mm to as long
as above 100 mm. In an illustrative embodiment, for example, from
about 15 mm to about 25 mm, for example, may comprise a length to
conveniently position slit patterns for adjacent sheets. However,
likewise, an embodiment may employ from about 35 mm to about 106
mm, as another example. [0055] 2. slit angle in these examples is
shown relative to a direction substantially perpendicular to fiber
direction using a right hand (e.g., counter-clockwise) rotation
(e.g., reference numeral 1140 of FIG. 12); slit angle may influence
cutting speed and/or surface aesthetics; for example, deviating
from an angle of zero increases the number of columns and, hence,
cutting time, since additional columns of slits would be cut to
substantially cover a sheet; a 45 degree angle, for example, may
increase cutting time by about 40%; additionally, it has been found
that slit angle may influence surface aesthetics; a slit angle
around above 60 degrees to below 80 degrees provides acceptable
aesthetics, but may increase cutting time several times over; thus,
in one possible embodiment, a 45 degree angle may present a
compromise. [0056] 3. distance (e.g., separation) between slits in
a column of slits (e.g., reference numeral 1310 of FIG. 13) may
influence substantial conformability of material to a mold surface
and/or affect potential expansion length (e.g., stretching of a
sheet); smaller fiber lengths may enhance conformability and/or may
improve quality of compound curves; a recommended range, for
example, may comprise from about 25 mm to about 75 mm; wrinkles may
become noticeable for compound curved surfaces for fiber lengths
longer than 60 mm; typically, a 40 mm fiber length shows less
wrinkling than 60 mm, and, typically, a 20 mm fiber length makes
wrinkling barely noticeable; however, fiber strand length may also
affect slit density which may potentially affect cutting time, as
described previously in connection with slit length; in an
illustrative embodiment, a distance or slit separation from about
20 mm to about 40 mm may be employed to produce acceptable quality
thermoplastic composite parts that substantially conform to a tool
surface without perceptible wrinkles; this fiber strand length also
may also be convenient for slit pattern matching to an adjacent
sheet and may provide a workable amount of column overlap, as
described previously and as discussed below in item 4; this length
may also be suitable for 48''.times.96'' (1.22 m.times.2.44 m)
sheets, which comprises a commonly supplied sheet size for
thermoforming; nonetheless, there may be situations for larger
parts (e.g., greater than one square meter) with gentle compound
surfaces in which longer fiber strand lengths may be desirable; for
larger parts, as an example, a fiber length on the order of from
about 100 mm to about 150 mm may be desirable. [0057] 4. overlap
between neighboring, immediately adjacent, columns was described
previously (e.g., reference numeral 1210 of FIG. 14), and may, for
example, be in the range from about 2 mm to about 5 mm, for an
illustrative embodiment.
[0058] In an embodiment, slits may be made in a pattern comprising
one or more adjacent vertical columns. As mentioned, slits may be
described without loss of generality, for an embodiment, by the
terms slit length, slit angle, and/or distance between slits.
Likewise, in an example embodiment, slits in a column may be
substantially aligned (e.g., parallel). Furthermore, for an
embodiment, for immediately adjacent, neighboring, columns, slits
in a right side column are located within a right edge of an
immediately adjacent, neighboring, left side column by an overlap
distance so that cutting of continuous fibers by slits takes place
even for fibers located at or near the edges of adjacent columns.
For example, an overlap is illustrated in FIG. 14 with reference
numeral 1210. For example, an overlap may comprise from about 0.5
mm to about 10 mm with a typical overlap of about 2 mm. Likewise,
an overlap may vary from column to column. More typically, however,
a sheet may be substantially covered with similar vertical columns
of slits. It is noted that without an overlap for adjacent columns,
it might be possible to have uncut continuous fibers between
adjacent columns, which may adversely affect fabrication during
vacuum forming, for example.
[0059] Thus, from column to column, slit length, slit angle and/or
distance (e.g., separation) between slits may, of course, be
varied; however, for convenience of manufacturing, a substantially
uniform pattern of consistent, substantially equal amounts, such as
for slit length, slit angle and/or distance (e.g., separation)
between slits, may be employed. Thus, oblique angles and their
supplements (e.g., supplementary angles) may be substantially equal
across columns. Distance or separation between slits of a column
may be substantially equal across columns. Length of slits of a
column may be substantially equal across columns. Further, for any
two adjacent neighbor columns, slits of one column are not aligned
horizontally relative to slits of its immediately adjacent,
neighboring columns.
[0060] A variety of approaches to cutting a polymer sheet to form a
pattern of slits may be employed with satisfactory results;
however, two or three example illustrations are provided. For
example, as described in more detail below, a knife blade, such as
a rotary knife blade, or a laser, such as a CO2, laser may be used.
As previously indicated, it is not intended that claimed subject
matter be limited to illustrative embodiments. For example,
composite polymer sheets may be available on spools, such as 510
and 520, from manufacturers, such as Polystrand, as one example,
and may be placed on a holding fixture, such as shown in FIG.
16.
[0061] In an embodiment, a holding fixture 510 may, for example,
accommodate spooled composite material, such as previously
described. Likewise, a tensioning mechanism, such as guides 530,
may allow for substantially consistent unwinding. For example,
material may be fed through guides and a laser cutting bed, which
may, for example, comprise a box with a thin honeycomb metal sheet
inside that the laser does not slice or cut. Material may be fed
through additional guides to a second spool to permit winding of
material after being sliced substantially in accordance with a
chosen pattern by electromagnetic energy emitted from the laser.
For example, a spool form, as shown, may be implemented via
mechanical pulling to unwind material from the first spool.
[0062] As material passes over laser bed 550, a CO2 laser, such as
540, for example, may be used to cut a slit pattern. A laser
comprises one example approach that allows for simple, fast, and/or
cost effective changing of a slit pattern, if desired, such as via
programming directionality and/or position with respect to an
emitted laser beam, for example. Likewise, some fiber reinforcement
material may be abrasive for a knife cutting system. Nonetheless,
alternately, a knife blade arrangement could be used, such as a
rotary knife blade, as mentioned, to cut a slit pattern. Thus, a
spool having a base slit pattern and a spool having an offset base
pattern may be produced in such a manner, for example.
[0063] One example technique to join two sheets to form a panel is
illustrated in FIG. 17. For example, if one spool of material, 610,
has a pattern of slits (referred to here for convenience as a base
pattern), such as may be made as described above, and if another
spool of material, 620, has a substantially similar pattern of
slits (referred to here for convenience as an offset pattern), such
as one offset vertically, again, for example, made as previously
described, a composite panel may be formed by feeding material of
appropriately aligned patterns, such as 650 and 660, through heated
rollers that may also apply pressure, for example. As a result of
heat and pressure, in this example, a composite panel material 670
may be formed and wound onto spool 630, for example.
[0064] Alternatively, sheets may be cut to panel size and placed in
physical contact substantially according to a desired orientation
of fibers. Thus, in this example embodiment, to produce a panel,
two sheets with slit patterns may be mutually adjacent with fibers
running in substantially the same direction (e.g., for fiber
reinforced polymer composite sheets). However, as discussed, one
sheet may have a pattern of slits that is offset (e.g., relative to
a sheet also having a pattern of slits), illustrated by various
previously discussed embodiments, to thereby produce a panel, in
another example embodiment.
[0065] Likewise, a panel, as an example, may comprise sheet pairs
stacked in 0/90/0/90 degree orientations until a desired panel
thickness is achieved, providing mechanical strength in
substantially orthogonal directions as a result of cross
orientation of reinforcing fibers. Nonetheless, sheet pairs may be
stacked in any degree orientation (e.g., 0/0/0/0 . . . 0/+45/-45/0
. . . , etc.). Intended properties of a part being fabricated may
influence how to orient sheet pairs relatively speaking, for
example. Likewise, a chosen sequence of relatively oriented sheet
pairs (e.g., in terms of degree rotation) may be repeated to
achieve a desired panel thickness. For example, if a sheet pair has
a thickness of 0.25 mm (2.times.0.125 mm), for a panel 2 mm thick,
8 sheet pairs may be stacked, such as in a degree orientation of
0/90/0/90/0/90/0/90, as an example.
[0066] A stack of sheet pairs, in an embodiment, may be placed on
Caul plates, for example, such as, one caul plate on the bottom,
and one on top. A "book" or "sandwich" formed may be placed on
heated hydraulic presses, as shown for example by an embodiment
depicted in FIG. 7. Press platens may be heated to a desired
temperature to melt a thermoplastic matrix material, for example.
Pressure may also be used. For example, at an appropriate time, a
press may be opened and the "book" or "sandwich" transferred to a
secondary press to allow cooling in a manner to potentially
beneficially affect rate of cooling (e.g., reduce warping, improve
surface finish, result in predictable laminate properties to reduce
de-lamination, etc.).
[0067] Thus, as discussed above, multiple "sheet pairs" may, for
example, in an embodiment, be stacked in any relative angular
orientation to fabricate a part, although, again, previously
described are merely illustrative example embodiments. FIG. 7, for
example, illustrates a pair 1910 and a pair 1920 with a sheet of
polymer 1930, for example, inserted between. Thus, these may be
joined to form panel 1940 in an embodiment, as shown. More
specifically, a panel may comprise one pair or more than one pair
in an embodiment, such as a stack.
[0068] Likewise, additional resin films, for example, may be placed
as an outer surface of a stack of sheet pairs to improve surface
finish, or may be interleaved between one or more sheet pairs of a
stack for a variety of reasons, such as described with respect to
FIG. 7, above, including to potentially facilitate at least
partially filling gaps or openings that might be produced during
thermoforming, for example.
[0069] In an embodiment, a panel, having been manufactured, may be
used in a standard vacuum forming machine to produce a three
dimensional composite part with properties close to properties of a
part made from continuous fiber reinforced laminates. For example,
it may be the case that by cutting a pattern of slits in
uni-directional sheets, and employing an offset alignment between
two adjacent sheets, in an example embodiment, a polymer sheet of
discontinuous reinforcing fibers is able to stretch during vacuum
forming, but `openings` created at slit locations may potentially
be bridged during vacuum forming, for example, by discontinuous
reinforcing fibers of an adjacent sheet, in an embodiment. A
discontinuous fiber of an immediately adjacent, neighboring sheet,
for example, may potentially, in a fabricated part, assist with
distributing a load across an associated `opening,` for
example.
[0070] In an example embodiment, a method of forming a composite
part may comprise the following. A discontinuous fiber reinforced
composite panel may be heated to a temperature so that a panel
becomes pliable. A vacuum may be formed so that the heated panel
stretches so as to substantially conform to a mold having a shape
that includes compound curves. In this context, the term compound
curve refers to a curve having more than one geometric center. For
example, for a three-dimensional shape, if a plane were to slice
the shape in a manner substantially perpendicular to its surface, a
curve formed at the intersection of the plane and the shape
comprises a compound curve if that curve has more than one
geometric center. The panel, after being shaped, may then be
cooled. In another embodiment, in addition to heat, pressure may
also be employed. Pressure may facilitate and/or improve the
capability of the panel to conform, at least substantially to the
shape of the mold. An applied pressure to a heated composite panel
of 100 psi, for example, has been shown to produce a part with
desired replication of a tool surface. Furthermore, pressure may
also improve consolidation between sheet pairs for thicker
panels.
[0071] It is noted that although a panel may be stretched to
conform its shape, a reasonable limit on degree of stretching
exists. For example, in an embodiment, before being stretched,
discontinuous fiber strands embedded in a panel, typically are in
reasonably close physical proximity and/or contact with other
discontinuous fibers. For an embodiment, this was discussed
previously in connection with FIG. 8. Thus, for an embodiment, it
may be desirable to limit stretching so that nearly all
discontinuous fibers in a panel in contact with another
discontinuous fiber before stretching also remain in contact after
stretching, for example, as illustrated in FIG. 9, discussed
previously.
[0072] FIG. 18 illustrates an embodiment of a typical vacuum
forming machine. A machine like this one may be employed for
fabrication of a part using a composite material, such as a panel.
Of course, this is merely one example illustration of a machine.
Thus, other machine arrangements for vacuum forming, for example,
are intended to be included within claimed subject matter.
[0073] Nonetheless, referring to FIG. 18, a panel, illustrated in
FIG. 18 as thermoplastic 1420, may be clamped, such as via toggle
clamps 1415, for example. Heater 1410 may heat panel 1420. It is
noted that a heater may be sufficiently sophisticated to be able to
program heating of different sections or zones to different
temperatures at different times or at different rates of
temperature change, for example. Eventually, an appropriate
temperature (or appropriate temperatures for multiple zones) for
forming a part may be reached.
[0074] Typically, a panel may therefore become pliable and able to
fold onto a tool. Thus, heater 1410 may be adjusted away and a
mold, such as 1430, may be moved into a position to receive the
pliable material. Likewise, typically at a concurrent time, a
vacuum may be initiated, illustrated by pump 1450. Thus, air may be
sucked out from between mold 1430 of the tool and panel 1420 to
permit the pliable panel to more tightly substantially conform to a
shape provided by the mold 1430. It is noted that vent holes may
permit air to be removed via the vacuum. Likewise, a reasonably
quick process may be employed so that cooling does not result in
stiffening of composite material too soon. However, after a pliable
panel substantially conforms to a desired shape, cooling becomes
desirable, so that the shape formed becomes reasonably stable. At
an appropriate time, therefore, having acquired a shape, a
resulting part may be removed from the tool, possibly for trimming
and/or other types of finishing. For example, a fabricated part may
have dimensions of the part are in the range of about 0.02 square
meters to about 4.0 square meters, although claimed subject matter
is not limited in scope in this respect.
[0075] In some situations, a combination of vacuum and pressure
forming may be desirable. Thus, a positive pressure may be employed
to press material against the tool surface. Thus, vacuum may be
used to pull material to the tool surface and pressure may be used
in combination to press the material to the tool surface.
[0076] Likewise, in other situations, compression molding may also
be employed, for example. In a typical embodiment, a flat part may
be cut from a composite sheet or panel to be heated to a melting
temperature and placed on a compression tool, for example. The tool
may close and press the material to a tool surface. After cooling,
the tool may be opened and a molded part may be removed.
[0077] Although claimed subject matter is not limited to
thermoplastic and/or thermoforming; nonetheless, thermoforming may
provide some advantages, such as, for example, a capability to
produce reasonably heavy parts (e.g., up to 125 Kg), a capability
to manufacture reasonably large parts, (e.g., up to 4 square
meters), an ability to provide flexible wall thickness (e.g., 1 mm
to 16 mm), an improved cost effectiveness for small batch
production due at least in part to comparatively low tooling cost,
a reasonably low cost to make modifications to a part, and/or a
capability to re-use material, such as through re-shaping. Some
additional related aspects include: reduced weight, stability at
room temperature, capability to reform shape, short cycle times,
and less waste in terms of heat and/or scrap.
[0078] In general, a desire exists to fabricate composite parts at
relatively low cost as a replacement for steel. Likewise, reducing
cycle time for production of relatively large composite parts to
less than 3 minutes is also desirable. Vacuum forming of panels may
at least partially address these desires. Likewise, continuous
fiber reinforced polymer composite materials offer a range of
benefits for fabrication of lightweight parts; however, broad
adoption of these materials may be constrained by a desire to
manufacture complex parts (e.g., having compound curves).
Alternatives, such as co-mingled fabrics and/or compression molding
generally may not be adequate; either because wrinkles may result
and/or because, to limit wrinkles, complex surfaces are a challenge
to fabricate. However, reinforcement using discontinuous fiber
strands may provide a potential approach to complex parts with
sufficient strength, adequately reduced cycle time and a limited
amount of wrinkling. Although claimed subject matter includes
thermoset materials, it is also noted that thermoplastics may
provide additional benefits, as alluded to above.
[0079] In the preceding description, various aspects of claimed
subject matter have been described. For purposes of explanation,
specifics, such as amounts, systems and/or configurations, as
examples, were set forth. In other instances, well-known features
were omitted and/or simplified so as not to obscure claimed subject
matter. While certain features have been illustrated and/or
described herein, many modifications, substitutions, changes and/or
equivalents will now occur to those skilled in the art. It is,
therefore, to be understood that the appended claims are intended
to cover all modifications and/or changes as fall within claimed
subject matter.
* * * * *