U.S. patent application number 16/382288 was filed with the patent office on 2019-08-01 for method and apparatus for forming a composite laminate stack using a breathable polyethylene vacuum film.
The applicant listed for this patent is BOMBARDIER INC.. Invention is credited to Louis FERNANDES, Thomas RIGUIDEL.
Application Number | 20190232576 16/382288 |
Document ID | / |
Family ID | 52629644 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190232576 |
Kind Code |
A1 |
FERNANDES; Louis ; et
al. |
August 1, 2019 |
METHOD AND APPARATUS FOR FORMING A COMPOSITE LAMINATE STACK USING A
BREATHABLE POLYETHYLENE VACUUM FILM
Abstract
A method for forming a shaped composite structure. The method
includes laying a composite laminate stack onto a mold, where the
composite laminate stack comprises fabric laminate and resin and
wherein the mold presents a predetermined shape, draping a vacuum
film comprising polyethylene onto the composite laminate stack,
thereby establishing an evacuatable volume between the vacuum film
and the mold, applying suction to the evacuatable volume between
the mold and the vacuum film to establish at least a partial vacuum
within the evacuatable volume, thereby compressing the composite
laminate stack via pressure applied to the vacuum film responsive
to the at least partial vacuum within the evacuatable volume, and
heating the composite laminate stack while applying suction to the
evacuatable volume, thereby at least partially consolidating the
laminate stack.
Inventors: |
FERNANDES; Louis; (Laval,
CA) ; RIGUIDEL; Thomas; (Montreal, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOMBARDIER INC. |
Dorval |
|
CA |
|
|
Family ID: |
52629644 |
Appl. No.: |
16/382288 |
Filed: |
April 12, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15122259 |
Aug 29, 2016 |
10293559 |
|
|
PCT/IB2015/051436 |
Feb 26, 2015 |
|
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16382288 |
|
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61947716 |
Mar 4, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29D 99/0003 20130101;
B29C 2035/0822 20130101; B29K 2995/0027 20130101; B29K 2995/0077
20130101; B29K 2307/04 20130101; B29K 2823/06 20130101; B29C
35/0805 20130101; B29K 2313/00 20130101; B29C 43/3642 20130101;
B29C 70/446 20130101; B29K 2995/0081 20130101; B29C 2043/3644
20130101; B29L 2031/3076 20130101; B29C 70/548 20130101 |
International
Class: |
B29C 70/44 20060101
B29C070/44; B29C 35/08 20060101 B29C035/08; B29C 70/54 20060101
B29C070/54; B29D 99/00 20060101 B29D099/00; B29C 43/36 20060101
B29C043/36 |
Claims
1.-8. (canceled)
9. A vacuum film suitable for use in compacting a composite
laminate stack of at least two fiber layers against a mold, the
vacuum film, comprising: polyethylene having a first surface and a
second, opposing surface, and a surface pattern, disposed on at
least one of the first surface and the second surface, comprising a
network of channels suitable for evacuating gasses from between the
vacuum film and the mold.
10. The vacuum film of claim 9, wherein: the vacuum film has a
thickness of between 9.5 mils (0.24 mm).+-.10%; the vacuum film is
transparent to infrared electromagnetic radiation with a wavelength
within a range of about 700 nm-1 mm the vacuum film has a tensile
elongation in a machine direction of between about 500-550%; the
vacuum film has a tensile elongation in a transverse direction of
between about 650-700%; the vacuum film has a tensile strength in
the machine direction of between about 3300-3500 psi; the vacuum
film has a tensile strength in the transverse direction of between
about 2700-2900 psi; the vacuum film has an Elemendorf tear
strength in the machine direction of between about 0.6-0.8 lb/mil;
the vacuum film has an Elemendorf tear strength in the transverse
direction of between about 0.9-1.1 lb/mil; the channels have a
width of between about 11.2 mils (0.28 mm).+-.10%; the channels
have a depth of between about 6 mils (0.15 mm).+-.10%; and the
channels are disposed apart from one another by a separation
distance of between about 84.8 mils (2.15 mm).+-.10%.
11. The vacuum film of claim 9, wherein the surface pattern
comprises at least one of a rectilinear grid pattern of the
channels or a diamond pattern of the channels.
12. The vacuum film of claim 9, wherein the vacuum film has a
tensile elongation in the machine direction of about 525% and a
tensile elongation in the transverse direction of about 675%.
13. The vacuum film of claim 9, wherein the vacuum film has a
tensile strength in the machine direction of about 3400 psi and a
tensile strength in the transverse direction of about 2800 psi.
15. The vacuum film of claim 9, wherein the vacuum film has an
Elemendorf tear strength in the machine direction of about 0.7
lb/mil and an Elemendorf tear strength in the transverse direction
of about 1.0 lb/mil.
16. The vacuum film of claim 9, wherein the vacuum film resists
deformation in a temperature range of at least one of between about
110-130.degree. F. (43.33-54.55.degree. C.), between about
115-125.degree. F. (46.11-51.67.degree. C.), or about 120.degree.
F. (48.89.degree. C.).
17.-20. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This International PCT Patent Application relies for
priority on U.S. Provisional Patent Application Ser. No. 61/947,716
filed on Mar. 4, 2014, the entire content of which is incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The present invention concerns a method and apparatus for
forming a composite laminate stack using a breathable polyethylene
vacuum film.
DESCRIPTION OF THE RELATED ART
[0003] in the construction of a composite material, it is known to
stack layers of composite laminate material onto a mold. The
composite laminate layers also are stacked on top of one another
and compressed using a vacuum that is applied using a vacuum film
(sometimes also referred to as a "vacuum bag"). So that air may be
removed from the space between the vacuum film and the mold, a
breather material is interposed between the composite laminate
layers and the vacuum film. While the vacuum is applied, the
composite laminate layers are heated simultaneously. The
application of heat and pressure (via the vacuum and/or positive
pressure) consolidates the composite laminate layers into a
composite laminate structure.
[0004] Conventionally, the vacuum film is made from a silicone or a
nylon based material, which is flexible and establishes a suitable
seal to establish a partial vacuum within the space between the
vacuum film and the mold.
[0005] One difficulty with silicone is that silicone used for hot
forming applications tends to stretch and deform, causing
variations in the laminate thickness due to a non-uniform pressure
distribution, especially when vacuum and/or heat is applied. While
this may not be problematic in every instance where a composite
laminate structure is being created, the problem becomes
exaggerated when the composite laminate materials are placed onto a
mold for the formation of stringers that have more complex shapes,
such as A-shaped stringers or .OMEGA.-shaped stringers.
[0006] For reference, a stringer is a structural strengthening
element that is attached to another element, such as a fairing, to
reinforce the other element and increase the strength and rigidity
of that other element. While stringers may have any of a number of
shapes, stringers may be constructed with a .DELTA.-shape or
.OMEGA.-shape, which are considered to be complex shapes for
composite stringers
[0007] To date, the prior art has not provided a suitable
substitute for the silicone vacuum film.
SUMMARY OF THE INVENTION
[0008] The present invention addresses one or more of the
deficiencies noted with respect to the prior art. In particular,
the present invention provides for a method for forming a shaped
composite structure. The method includes laying a composite
laminate stack onto a mold, where the composite laminate stack
comprises fabric laminate and resin and wherein the mold presents a
predetermined shape, draping a vacuum film comprising polyethylene
onto the composite laminate stack, thereby establishing an
evacuatable volume between the vacuum film and the mold, applying
suction to the evacuatable volume between the mold and the vacuum
film to establish at least a partial vacuum within the evacuatable
volume, thereby compressing the composite laminate stack via
pressure applied to the vacuum film responsive to the at least
partial vacuum within the evacuatable volume, and heating the
composite laminate stack while applying suction to the evacuatable
volume, thereby at least partially consolidating the laminate
stack.
[0009] In one contemplated embodiment, the resin is pre-impregnated
into at least a portion of the composite laminate stack.
[0010] In another contemplated embodiment, the heating step include
the application of infrared electromagnetic radiation at least
through the vacuum film within a wavelength range between at least
one of about 700 nm-1 mm, 2-10 .mu.m, or 1.5-8 .mu.m.
[0011] Still further, the heating step is contemplated to occur at
a temperature of at least one of between about 110-130.degree. F.
(43.33-54.55.degree. C.), between about 115-125.degree. F.
(46.11-51.67.degree. C.), or about 120.degree. F. (48.89.degree.
C.).
[0012] Concerning the mold, the predetermined shape may include at
least one of an .OMEGA.-shaped or a .DELTA.-shaped surface.
[0013] It is contemplated that the fabric laminate may include
carbon fibers, among other types of fibers.
[0014] In addition, one side of the vacuum is contemplated to
include a pattern of channels, permitting gases to be evacuated
when the suction is applied to the evacuatable volume. The pattern
may be a rectilinear grid pattern of the channels or a diamond
pattern of the channels, among other patterns.
[0015] The present invention also provides for a vacuum film
suitable for use in compacting a composite laminate stack of at
least two fiber layers against a mold. The vacuum film includes
polyethylene having a first surface and a second, opposing surface,
and a surface pattern, disposed on at least one of the first
surface and the second surface. The surface pattern includes a
network of channels suitable for evacuating gasses from between the
vacuum film and the mold.
[0016] In one contemplated embodiment, the vacuum film has a
thickness of between 9.5 mils (0.24 mm).+-.10%, is transparent to
infrared electromagnetic radiation with a wavelength within a range
of about 700 nm 1 mm, has a tensile elongation in a machine
direction of between about 500-550%, has a tensile elongation in a
transverse direction of between about 650-700%, has a tensile
strength in the machine direction of between about 3300-3500 psi,
has a tensile strength in the transverse direction of between about
2700-2900 psi, has an Elemendorf tear strength in the machine
direction of between about 0.6-0.8 lb/mil, and has an Elemendorf
tear strength in the transverse direction of between about 0.9-1.1
lb/mil. In addition, the channels are contemplated to have a width
of between about 11.2 mils (0.28 mm).+-.10%, a depth of between
about 6 mils (0.15 mm).+-.10%, and are disposed apart from one
another by a separation distance of between about 84.8 mils (2.15
mm).+-.10%.
[0017] It is contemplated that the surface pattern may have a
rectilinear grid pattern of the channels or a diamond pattern of
the channels.
[0018] In addition, it is contemplated that the vacuum film may
have a tensile elongation in the machine direction of about 525%
and a tensile elongation in the transverse direction of about
675%.
[0019] Furthermore, it is contemplated that the vacuum film may
have a tensile strength in the machine direction of about 3400 psi
and a tensile strength in the transverse direction of about 2800
psi.
[0020] Next, the vacuum film may have an Elemendorf tear strength
in the machine direction of about 0.7 lb/mil and an Elemendorf tear
strength in the transverse direction of about 1.0 lb/mil.
[0021] Also, the vacuum film is contemplated to resist deformation
in a temperature range of at least one of between about
110-130.degree. F. (43.33-54.55.degree. C.), between about
115-125.degree. F. (46.11-51.67.degree. C.), or about 120.degree.
F. (48.89.degree. C.).
[0022] The present invention also provides for a method for forming
a shaped composite structure. The method is contemplated to include
laying a composite laminate stack onto a mold, where the composite
laminate stack comprises fabric laminate and resin and wherein the
mold presents a predetermined shape, draping a vacuum film onto the
composite laminate stack, thereby establishing an evacuatable
volume between the vacuum film and the mold, the vacuum film,
applying suction to the evacuatable volume between the mold and the
vacuum film to establish at least a partial vacuum within the
evacuatable volume, thereby compressing the composite laminate
stack against the mold, and heating the composite laminate stack
while applying suction to the evacuatable volume, thereby at least
partially consolidating the laminate stack. The vacuum film is
contemplated to resist deformation when exposed to infrared
electromagnetic radiation having a wavelength within a range of
about 700 nm-1 mm and a temperature range of between about
110-130.degree. F. (43.33-54.55.degree. C.).
[0023] The vacuum film may be made from, among other materials,
polyethylene.
[0024] One side of the vacuum film comprises may include a pattern
of channels, permitting gases to be evacuated when the suction is
applied to the evacuatable volume.
[0025] The pattern may be a rectilinear grid pattern of the
channels or a diamond pattern of the channels, among other possible
patterns.
[0026] Still other aspects of the present invention will be made
apparent from the discussion at follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present invention will now be described in connection
with the drawings appended hereto, in which:
[0028] FIG. 1 is a graphical representation of a cross-section of
an arrangement of components for the creation of a consolidated,
composite laminate stack according to the prior art;
[0029] FIG. 2 is a graphical representation of a cross-section of
an arrangement of components for the creation of a consolidated,
composite laminate stack according to the present invention;
[0030] FIG. 3 is a graphical, cross-sectional side view of various
stress points applicable to a vacuum film placed upon an
.OMEGA.-shaped feature on a mold for forming a consolidated,
composite laminate stack;
[0031] FIG. 4 is a graphical representation of a top view of a
portion of a breathable vacuum film according to the present
invention;
[0032] FIG. 5 is a graphical, cross-sectional side view of a first
contemplated construction of the breathable vacuum film illustrated
in FIG. 4; and
[0033] FIG. 6 is a graphical, cross-sectional side view of a second
contemplated construction of the breathable vacuum film illustrated
in FIG. 4.
DETAILED DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION
[0034] The present invention will now be described in connection
with one or more embodiments. The discussion of any one particular
embodiment or associated feature is not intended to be limiting of
the present invention. To the contrary, the discussion of
particular embodiments and features is intended to illustrate the
breadth and scope of the present invention. There are numerous
variations and equivalents that will be made apparent from the
discussion that follows. Those variations and equivalents are
intended to be encompassed by the scope of the present invention as
if described herein.
[0035] With respect to various features that are discussed in
connection with specific embodiments, it is noted that the features
are not intended to be exclusive of one another. To the contrary,
as should be apparent to those skilled in the art, several of the
features may be combinable in arrangements that differ from the
specific embodiments described below. Those combinations are
contemplated to fall within the scope of the present invention.
[0036] FIG. 1 is a graphical side view of a cross-section of one
example in the prior art for a consolidation apparatus 10, which is
defined herein as an arrangement of components for the creation of
a consolidated, composite laminate stack.
[0037] A consolidated, composite laminate stack may have many
applications and be suitable for any of a number of installations.
Among them, the consolidated, composite laminate stack may be used
for the creation of a component for an aircraft. The aircraft
component may be a stringer, fuselage panel, engine fairing, or any
other component.
[0038] Typically, a composite laminate stack 12 is made from at
least two layers of fiber laminate 14, 16, which could be carbon
fiber laminate layers, for example, Although two layers of carbon
fiber laminate 14, 16 are shown in FIGS. 1 and 2 for the sake of
simplicity, it should be understood that many more layers of carbon
fiber laminate 14, 16 may be employed without departing from the
scope of the present invention. In the manufacture of a stringer
for an aircraft, it is not uncommon for the composite laminate
stack 12 to include between about nine to twenty layers of carbon
laminate, for example. The layers of carbon fiber laminate 14, 16
may include prepreg laminate layers.
[0039] As shown in FIG. 1, the layers of carbon fiber laminate 14,
16 are stacked on top of a mold 18. In the illustrated example, the
mold includes a .DELTA.-shaped feature 20. The mold 18 establishes
the shape for the consolidated, composite laminate stack 12
produced by the consolidation apparatus 10.
[0040] So that the layers of carbon fiber laminate 14, 16 may be
consolidated, the layers of carbon fiber laminate 14, 16 are
compacted by application of pressure P resulting from the
application of a vacuum (or partial vacuum) between a vacuum film
22 and the mold 18. The space between the vacuum film 22 and the
mold 18 also is referred to as an evacuatable volume 24. In this
prior art version of the consolidation apparatus 10, the vacuum
film 22 is made from a silicone or nylon based material.
[0041] A breather material 26 and a first release layer 28 are
inserted between the composite laminate stack 12 and the vacuum
film 22. The breather material 26 is typically made from a cloth
material or laminate. The breather material 26 establishes an air
volume between the vacuum film 22 and the composite laminate stack
12 to facilitate the removal of air from the evacuatable volume
24.
[0042] So that the silicone vacuum film 22 and the breather
material 24 easily separate from the composite laminate stack 12, a
first release layer 28 typically is inserted between the breather
material 24 and the composite laminate stack 12. Similarly, to
facilitate separation of the composite laminate stack 12 from the
mold 18, a second release layer 30 typically is inserted between
the composite laminate stack 12 and the mold 18.
[0043] To apply a vacuum or partial vacuum in the evacuatable
volume 24 between the vacuum film 22 and the mold 18, the vacuum
film 22 is provided with a connector 32 that connects to a vacuum
source 34 via a vacuum line 36. A seal 38 may be provided around
the periphery of the vacuum film 22 to assure an airtight seal
around the mold 18.
[0044] During consolidation of the composite laminate stack 12, a
vacuum is applied in the evacuatable volume 24 between the vacuum
film 22 and the mold 18. At the same time, the composite laminate
stack 12 is heated. Heat may be applied from an area within the
mold 18 and/or from a source external to the mold 18. For example,
heat may be applied via heating elements within the mold 18. In
addition, heat may be applied via heat lamps positioned near to the
mold 18 (e.g., above the mold 18), external to the vacuum film 22.
Heat may be applied in other ways, as should be apparent to those
skilled in the art.
[0045] A deficiency with existing silicone vacuum films is that
when they are used to form .DELTA.-shaped stringers 18, such as the
one shown (or .OMEGA.-shaped stringers), and heat is applied, the
silicone tends to stretch and deform in areas where the shape makes
significant transitions, such as at the apex of the .DELTA. or
adjacent to the bottom ends of the .OMEGA. where the ends
transition to the horizontally-oriented features. Deformation of
the silicone vacuum film may result in an inadequately formed
stringer (or other component), which may result ultimately in the
rejection of the component for service.
[0046] FIG. 3 is a graphical, cross-sectional side view of various
stress points S associated with a vacuum film 44 placed upon an
.OMEGA.-shaped feature 76 that is part of a mold 18 for forming a
consolidated, composite laminate stack 12 (omitted in this view).
The stress points S are associated with transition regions, as
noted above. In the case where the vacuum film 44 is a silicone
vacuum film, the silicone material tends to stretch and deform at
the stress points S, also as noted. This may result in an
improperly formed composite laminate stack 12.
[0047] In accordance with a non-limiting example of the present
invention, the composite laminate stack 12 typically is
pre-impregnated with resin (also referred to as a prepreg
material). During the application of both heat and pressure, the
resin impregnates the material fibers and migrates such that
adjacent composite layers 14, 16 in the composite laminate stack 12
become adhered to one another. This process is referred to as
consolidation or coalescing herein. After the heat and pressure are
discontinued and the composite laminate stack 12 cools, the
consolidated composite laminate stack 12 retains the shape of the
mold 18.
[0048] Reference is now made to FIG. 2, which describes the present
invention with reference to the conventional example, as
illustrated and discussed in connection with FIG. 1.
[0049] By way of introduction, and by comparison with the
consolidation apparatus illustrated in FIG. 1, it is noted that,
for the consolidation apparatus 40 of the present invention,
release strips 42 have been added. In addition, the vacuum film 22
has been replaced by an auto-breather vacuum film 44 (also referred
to herein as a breathable film 44). In addition, the breather
material 26 has been eliminated.
[0050] In the consolidation apparatus 40 of the present invention,
to create a consolidated composite laminate stack 12 in a
predetermined shape, it is contemplated that the composite laminate
stack 12 will be placed on top of the mold 18 including, for
example, the .DELTA.-shaped portion 20. While it is contemplated
that individual laminate layers 14, 16 may be stacked on top of one
another on the mold 18, it is anticipated that the composite
laminate stack 12 will be formed prior to placement onto the mold
18 and subsequently laid onto the mold 18 as a unit.
[0051] With respect to the composite laminate layers 14, 16, it is
noted that these layers 14, 16 are merely representative of a
plurality of composite laminate layers 14, 16 that may be stacked
and debulked (on a flat or a non-flat surface) before being stacked
on top of one another to form the composite laminate stack 12. As
indicated above, it is contemplated that the composite laminate
stack 12 will include more than just two single composite laminate
layers 14, 16. In fact, it is contemplated that approximately
twelve composite laminate layers 14, 16 or more may be stacked on
top of one another to form the consolidated, composite laminate
stack 12.
[0052] In the context of the present invention, it is contemplated
that the composite laminate layers 14, 16 will be made from
unidirectional carbon fiber laminates pre-impregnated with resin.
However, it is noted that the composite laminate layers 14, 16 may
be made from non-woven laminates. Separately, the composite
laminate layers 14, 16 may be made from materials other than carbon
fiber. For example, aramid fibers and para-aramid fibers (including
Kevlar.TM. (a trademark of EA DuPont de Nemours and Company)) and
other suitable materials may be employed without departing from the
scope of the present invention. Still further, the composite
laminate layers 14, 16 may be made from a combination of carbon
fibers, aramid fibers, para-aramid fibers, and other materials, as
should be apparent to those skilled in the art.
[0053] The resin may be any material that may be considered to be
suitable by those skilled in the art. Resins include, but are not
limited to, epoxy resins, polyester resins, vinylester resins, and
the like.
[0054] It is contemplated that the composite laminate layers 14, 16
may not include a resin, instead, the composite laminate layers 14,
16 may be treated in a fashion that facilitates consolidation
without the use of resin. In other words, the present invention
should not be considered to be limited to embodiments where each of
the composite laminate layers 14, 16 are pre-impregnated with
resin.
[0055] Variations also are contemplated to fall within the scope of
the present invention. For example, every other one of the
composite laminate layers 14, 16 may be pre-impregnated with resin.
Separately, the composite laminate layers 14, 16 may be free of
resin, which may be introduced before the application of heat and
pressure. Still further, the composite laminate layers 14, 16 may
be pre-impregnated with resin on selected areas, zones, or regions
thereof.
[0056] In the consolidation apparatus 40 of the present invention,
the auto-breather vacuum film 44 comprises polyethylene. As will be
made apparent from the discussion that follows, other materials
also may be employed without departing from the scope of the
present invention.
[0057] A vacuum bag comprising polyethylene (and in some cases
primarily polyethylene) has improved release characteristics by
comparison with silicone. For example, polyethylene is able to
resist deformation and/or elongation when exposed to a vacuum and
to heat, thereby allowing good compaction of the composite laminate
stack 12 against the tight curves of the mold 18.
[0058] With reference to FIG. 4, the auto-breather vacuum film 44
is contemplated to be provided with a grooved pattern 46 on at
least one surface thereof. The grooved pattern 46 is provided to
establish air channels between the auto-breather vacuum film 44 and
the composite laminate stack 12 (that is, within the evacuatable
space 24) that allows for the removal of air from the evacuatable
space 24. The grooved pattern 46 may include any repeating or
non-repeating pattern of grooves 48 as required or as desired.
Moreover, the grooved pattern 46 may change at different places on
the auto-breather vacuum film 44. In other words, a uniform grooved
pattern 46 need not be applied across the entire surface of the
auto-breather vacuum film 44. The auto-breather vacuum film 44 is
presented as a non-limiting, first embodiment of the auto-breather
vacuum film 44 according to the present invention.
[0059] With reference to FIG. 5, a non-limiting, second embodiment
of the auto-breather vacuum film according to the present invention
is illustrated and is labeled 44'. In this embodiment, the vacuum
film 44' includes a plurality of embossments 50, each of which form
the individual grooves 48 in the vacuum film 44'. Since the grooves
48 are formed through embossments 50, the top surface 52 and the
bottom surface 54 include the embossments 50. On the top surface
52, the embossments 50 are convex and on the bottom surface 54, the
embossments 50 are concave, thereby establishing the grooves 48 in
the vacuum film 44'.
[0060] With reference to FIG. 6, a non-limiting, third embodiment
of an auto-breather vacuum film is shown and is labeled 44''. Here,
the grooves 48 are formed by individual channels 56 that are cut,
molded, or otherwise formed in the bottom surface 54 of the
auto-breather vacuum film 44''.
[0061] As should be apparent from the foregoing, the grooves 48 may
be established in the auto-breather vacuum film 44, 44', 44'' via
any suitable manufacturing technique without departing from the
scope of the present invention. It is contemplated, however, that
the grooves 48 will be formed on at least the bottom surface 54 of
the vacuum film 44, 44', 44'' to establish air channels immediately
adjacent to the composite laminate stack 12 in the consolidation
apparatus 40.
[0062] With renewed reference to FIG. 2, it is noted that release
strips 42 are applied to regions of the composite laminate stack 12
to facilitate slippage of the composite laminate stack 12 during
application of the vacuum to the evacuatable volume 24.
[0063] As noted above, the auto-breather vacuum film 44, 44', 44''
is contemplated to be made from a polyethylene material, which
possesses suitable release characteristics. As a result, a first
release layer 28 may not be required for the consolidation
apparatus 40 of the present invention. It is contemplated that a
second release layer 30 will be provided between the composite
laminate stack 12 and the mold 18. Moreover, as noted above, in
selected locations, release strips 42 are contemplated to be added
to facilitate slippage of the composite laminate stack 12 with
respect to the mold 18 during consolidation.
[0064] With renewed reference to FIG. 4, the grooves 48 are shown
in a diamond-shaped pattern 46. While this pattern 46 is considered
to be suitable for the auto-breather vacuum film 44, 44', 44'' the
grooves 48 may follow any other suitable pattern without departing
from the scope of the present invention. For example, the grooves
48 may be set out in a rectilinear pattern, like a piece of graph
paper. Other patterns also may be employed, including curved
grooves 48, without departing from the scope of the present
invention.
[0065] With respect to the diamond shaped pattern 46 applied to the
vacuum film 44, 44', 44'' it is contemplated that individual
diamonds 58 will have a width 60 and a height 62 and be separated
from one another by a separation distance 64. The width 60 is
contemplated to be about 74.4 mils (74.4 thousandths of an inch)
(1.89 mm).+-.10%. The height 62 is contemplated to be about 129.7
mils (3.29 mm).+-.10%. The separation distance 64 is contemplated
to be about 84.8 mils (2.15 mm).+-.10%. Alternatively, the width 60
may be about 74.4 mils (1.89 mm).+-.5%, the height 62 may be about
129.7 mils (3.29 mm).+-.5%, and the separation distance 64 may be
about 84.8 mils (2.15 mm).+-.5%. In a further alternative, the
width 60 may be about 74.4 mils (1.89 mm).+-.2%, the height 62 may
be about 129.7 mils (3.29 mm).+-.2%, and the separation distance 64
may be about 84.8 mils (2.15 mm).+-.2%. As apparent, in the
illustrated embodiment, the width 60 may be about 74.4 mils (1.89
mm), the height 62 may be about 129.7 mils (3.29 mm), and the
separation distance 64 may be about 84.8 mils (2.15 mm).+-.2%.
[0066] With reference to FIG. 5, the auto-breather vacuum film 44'
may have a thickness 66 of about 9.5 mils (0.24 mm) with a groove
depth 68 of about 6 mils (0.15 mm).+-.10%. Alternatively, the
auto-breather vacuum film 44' may have a thickness 66 of about 9.5
mils (0.24 mm) with a groove depth 68 of about 6 mils (0.15
mm).+-.5%. In a further embodiment, the auto-breather vacuum film
44' may have a thickness 66 of about 9.5 mils (0.24 mm) with a
groove depth 68 of about 6 mils (0.15 mm).+-.2%. As may be
apparent, in the illustrated embodiment, the thickness 66 of the
auto-breather vacuum film 44' is about 9.5 mils (0.24 mm) and the
groove depth 68 is about 6 mils (0.15 mm).
[0067] With reference to FIG. 6, the auto-breather vacuum film 44''
may have a thickness 70 of about 9.5 mils (0.24 mm) with a groove
depth 72 of about 6 mils (0.15 mm).+-.10%. Alternatively, the
auto-breather vacuum film 44'' may have a thickness 70 of about 9.5
mils (0.2.4 mm) with a groove depth 72 of about 6 mils (0.15
mm).+-.5%. In a further embodiment, the auto-breather vacuum film
44'' may have a thickness 70 of about 9.5 mils (0.24 mm) with a
groove depth 72 of about 6 mils (0.15 mm).+-.2%. As should be
apparent, in the illustrated embodiment, the thickness 70 of the
auto-breather vacuum film 44'' is about 9.5 mils (0.24 mm) with a
groove depth 72 of about 6.5 mils (0.15 mm).
[0068] As noted above, the grooves 48 in the auto-breather vacuum
film 44, 44', 44'' establish air channels within in the evacuatable
space 24 that allow for the removal of air from the evacuatable
space 24. In particular, it is contemplated that the grooves 48
will be of a sufficient size, density, and spacing, to assure an
acceptable rate of air removal from the evacuatable space 24 and,
thereby, to assure the formation of a consolidated laminate stack
12 with desirable consolidation characteristics. In this manner,
the auto-breather vacuum film 44, 44', 44'' combines the
functionality of the vacuum film 22 and breather material 26 shown
in FIG. 1.
[0069] In connection with the thickness 70 of the auto-breather
vacuum film 44'', it is noted that the thickness 70 may fall within
a much larger range of about 5-12 mils (0.13 mm-0.30 mm). A smaller
thickness 70 is unlikely to provide a suitable amount of the
auto-breather film material for the formation of adequate grooves
48. A thickness 70 greater than 12 mils (0.30 mm) may become too
rigid to be useful as the auto-breather vacuum film 44''.
[0070] With respect to each embodiment of the auto-breather vacuum
film 44, 44', 44'', it is contemplated that the grooves 48 may have
a width of about 11.2 mils (0.28 mm).+-.10%. Alternatively, the
width 74 of the grooves 48 may be about 11.2 mils (0.28 mm).+-.5%.
In a further embodiment, the width 74 may be about 11.2 mils (0.28
mm).+-.2%. As may be apparent, in the illustrated embodiment, the
width 74 of the grooves 48 is about 11.2 mils (0.28 mm).
[0071] As indicated above, the composition of the auto-breather
vacuum film 44, 44', 44'' comprises polyethylene. Additives may be
included in the polyethylene without departing from the scope of
the present invention. For example, the polyethylene may include
titanium dioxide (<5.0%), lead (<1.0%), and chromium
(<0.1%), among other additive materials. One suitable material
for the vacuum bag is a material called "Embossed Polyethylene
Film" (product code DC500A) sold by Bloomer Plastics, Incorporated,
with a business address at 1710 North Industrial Drive, Bloomer,
Wis. 54724-0005 (as reported in the Material Safety Data Sheet
dated Aug. 11, 2011).
[0072] The present invention contemplates that the auto-breather
vacuum film 44, 44', 44'' will have a sufficient thickness to
assist with establishing an adequate vacuum in the evacuatable
space 24 between the vacuum film 44, 44', 44'' and the mold 18.
Moreover, it is contemplated that the auto-breather vacuum film 44,
44', 44'', since it is made from polyethylene, will resist
deformation when the vacuum is applied.
[0073] As noted above, to form the composite laminate stack 12,
heat is applied to the composite laminate layers 14, 16 during the
time that the vacuum is applied to the evacuatable volume 24
between the auto-breather vacuum film 44, 44', 44'' and the mold
18.
[0074] Heat may be applied by any type of heater. However, it is
contemplated that heat will be applied in the form of radiant heat.
To assure that maximal heat is transmitted to the composite
laminate layers 14, 16, the vacuum film 44, 44', 44'' is
contemplated to be transparent to infrared electromagnetic
radiation. More specifically, the auto-breather vacuum film 44,
44', 44'' is contemplated to be transparent to infrared
electromagnetic radiation with a wavelength of 700 nm-1 mm and a
frequency of 430 THz-300 GHz. More specifically, if the heat source
is a ceramic heating element, the auto-breather vacuum film 44,
44', 44'' is contemplated to be transparent to infrared
electromagnetic radiation with a wavelength in the range of between
about 2-10 .mu.m. If a quartz heat lamp is utilized, it is
contemplated that the auto-breather vacuum film 44, 44', 44'' will
be transparent to infrared electromagnetic radiation with a
wavelength in a range between about 1.5-8 .mu.m. As should be
apparent, other heat sources may be employed that generate infrared
electromagnetic radiation in other wavelength ranges.
[0075] While not considered to be limiting of the invention, it is
noted that plastics, such as polyvinylchloride and polyethylene,
have a peak absorption for infrared electromagnetic radiation of
around 3500 nm. Accordingly, it is contemplated that the source of
infrared electromagnetic radiation will be selected so as to avoid
the generation of heat within the wavelength of around 3500 nm to
avoid absorption by the polyethylene.
[0076] It is understood that the absorption properties of the
material used for the auto-breather vacuum film 44, 44', 44'' may
vary depending upon the additives incorporated into the
polyethylene. Accordingly, it may be necessary to tune the heating
source to the properties of the auto-breather vacuum film 44, 44',
44'' so that the auto-breather vacuum film 44, 44', 44'' exhibits
transparency at the primary wavelengths emitted by the heater.
[0077] It is also contemplated that the auto-breather vacuum film
44, 44', 44'' will be made from a material that is substantially
transparent to infrared electromagnetic radiation during the
consolidation process. In particular, it is contemplated that the
auto-breather vacuum film 44, 44', 44'' is transparent to infrared
electromagnetic radiation at an elevated temperature of between
about 110-130.degree. F. (43.33-54.55.degree. C.), between about
115-125.degree. F. (46.11-51.67.degree. C.), or about 120.degree.
F. (48.89.degree. C.). In other words, so that the composite
laminate layers 14, 16 forming the composite laminate stack 12 may
coalesce (or be consolidated) as a result of heating at one or more
of these temperatures, it is contemplated that the polyethylene
will be transparent (or substantially transparent) to the infrared
electromagnetic radiation at these temperatures. It is noted that
the temperature applied during the consolidation process is related
to the resin employed. Accordingly, temperatures different from
those described herein are contemplated to fall within the scope of
the present invention.
[0078] In addition, it is contemplated that the auto-breather
vacuum film 44, 44', 44'' will resist deformation, elongation, and
creep at these same temperatures of between about 110-130.degree.
F. (43.33-54.55.degree. C.), between about 115-12.5.degree. F.
(46.11-51.67.degree. C.), or about 120.degree. F. (48.89.degree.
C.). Being resistant to deformation, elongation, and creep at these
operating temperatures, the auto-breather vacuum film 44, 44', 44''
will resist changing its shape and, therefore, will assist in
compacting the composite laminate stack 12 against the mold until
the composite laminate stack 12 is consolidated into the shape that
is complimentary to the mold 18.
[0079] Concerning the grooves 48, it is contemplated that the
grooves 48, regardless of the manner in which they are formed in
the auto-breather vacuum film 44, 44', 44'' will have a
sufficiently robust cross-section and a sufficiently large
distribution to facilitate removal of air from the composite fabric
stack 12 to facilitate the consolidation (or coalescing) of the
layers 14, 16. As may be apparent, if the grooves 48 are too small
or there are too few grooves 48, the grooved pattern 46 may not
present sufficient channels for removal of air. If so, the
auto-breather vacuum film 44, 44', 44'' may not be able to apply
sufficient pressure P to the composite laminate stack 12 for the
composite laminate layers 14, 16 to coalesce (or consolidate) into
a unitary body.
[0080] Separately, it is contemplated that the auto-breather vacuum
film 44, 44', 44'' may be employed to consolidate the composite
laminate stack 12 at or near room temperature. In particular, the
auto-breather vacuum film 44, 44', 44'' may be used for a debulking
operation prior to consolidation. The debulking operation is
essentially the same as described above, except that heat is not
applied to activate the resin. Instead, the auto-breather vacuum
film 44, 44', 44'' may be laid on top of the composite laminate
stack 12 so that a vacuum may be applied to the evacuatable volume
24. The debulking operation is employed to compact the composite
laminate stack 12 prior to consolidation using heat. It is noted
that debunking the composite laminate stack 12 using the
auto-breather vacuum film 44, 44', 44'' improves debulking by 3-4%
or more (by comparison with the prior art using a nylon film and
breather material). It is noted that debulking operations may be
repeated, as necessary, during the construction of the composite
laminate stack 12 from a plurality of individual fabric layers.
[0081] As noted above, the present invention has been described in
connection with several embodiments and variations. The present
invention is not intended to be limited to any one particular
embodiment or to any one particular feature described herein. To
the contrary, there are numerous variations and equivalents that
those skilled in the art would appreciate in connection with the
present invention. Those variations and equivalents are intended to
be encompassed by the present invention.
* * * * *