U.S. patent application number 14/057254 was filed with the patent office on 2014-04-24 for surface engineering of thermoplastic materials and tooling.
This patent application is currently assigned to Cytec Industries Inc.. The applicant listed for this patent is Cytec Industries Inc.. Invention is credited to James Francis PRATTE, Scott Alfred ROGERS.
Application Number | 20140110633 14/057254 |
Document ID | / |
Family ID | 49546614 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140110633 |
Kind Code |
A1 |
PRATTE; James Francis ; et
al. |
April 24, 2014 |
Surface Engineering of Thermoplastic Materials and Tooling
Abstract
A prepared mold tool having a thermoplastic surface layer
polymer coating on the mold surface of the mold tool or prepared
prepreg having a thermoplastic surface layer polymer coating on the
surface of the thermoplastic fiber reinforced prepreg are described
that enhance first ply laydown of thermoplastic fiber reinforced
composite prepregs onto mold tools for prepreg forming or in situ
tape placement. Resulting thermoplastic fiber reinforced composite
parts from a thermoplastic fiber reinforced thermoplastic composite
material having structural reinforcement fibers with one or more
high performance polymers, and a thermoplastic surface layer
polymer coating which forms a polymer blend with the high
performance polymers of the thermoplastic fiber reinforced
composite material thereby imparting improved properties, and
methods for making and using same, are provided herein.
Inventors: |
PRATTE; James Francis;
(Wilmington, DE) ; ROGERS; Scott Alfred;
(Placentia, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cytec Industries Inc. |
Woodland Park |
NJ |
US |
|
|
Assignee: |
Cytec Industries Inc.
Woodland Park
NJ
|
Family ID: |
49546614 |
Appl. No.: |
14/057254 |
Filed: |
October 18, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61715438 |
Oct 18, 2012 |
|
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Current U.S.
Class: |
252/500 ;
156/272.6; 156/379.8; 264/39; 428/522 |
Current CPC
Class: |
B29C 33/68 20130101;
B29C 70/386 20130101; B29C 33/56 20130101; B29C 33/42 20130101;
B29K 2071/00 20130101; B29K 2105/0881 20130101; B32B 38/0008
20130101; B29C 37/0075 20130101; B32B 7/03 20190101; B29C 33/62
20130101; B29C 70/086 20130101; B29K 2079/085 20130101; B05D 1/10
20130101; B32B 2037/268 20130101; B29K 2101/12 20130101; B29B
15/105 20130101; Y10T 428/31935 20150401; B29C 33/3842
20130101 |
Class at
Publication: |
252/500 ;
156/379.8; 264/39; 156/272.6; 428/522 |
International
Class: |
B32B 7/00 20060101
B32B007/00 |
Claims
1. A tool for automated tape laying of in situ thermoplastic fiber
reinforced composite materials comprising: a non-porous solid metal
mold tool having a molding surface; and a thermoplastic surface
layer polymer; and a release film releasably interposed between the
mold surface of the mold tool and the thermoplastic surface layer
polymer.
2. The tool according to claim 1, wherein the mold surface of the
mold tool has a texture.
3. The tool according to claim 2, wherein the texture of the mold
surface of the mold tool is created by sandblasting with 40-120
grit glass beads.
4. The tool according to claim 2, wherein the texture of the mold
surface of the mold tool has a mean spacing of profile elements of
0.07 .mu.m or greater and a maximum height of profile of 5.0 or
greater.
5. The tool according to claim 1, wherein the thermoplastic surface
layer polymer is chosen from PEK, PEKK, PEEK or blends thereof.
6. The tool according to claim 1, wherein the thermoplastic surface
layer polymer further comprises one or more multi-functional
agents.
7. The tool according to claim 1, wherein the thermoplastic surface
layer polymer is a discontinuous plurality of well fused
thermoplastic particles releasably adhered to the release film.
8. The tool according to claim 1, wherein the thermoplastic surface
layer polymer is applied by plasma spray.
9. The tool according to claim 1, wherein the non-porous metal mold
tool having a mold surface further has texture; wherein the release
film adheres to the mold surface of the mold tool; and wherein the
thermoplastic surface layer polymer coating comprises a plurality
of thermoplastic surface layer polymer particles applied by plasma
spraying; wherein the thermoplastic surface layer polymer coating
is a discontinuous plurality of beads that are well fused
thermoplastic particles releasably adhered to the release film.
10. The tool according to claim 9 wherein the texture of the mold
surface of the mold tool has a mean spacing of profile elements
0.07 .mu.m or greater and a maximum height of profile about 5.0 or
greater.
11. The tool according to claim 9 wherein the thermoplastic surface
layer polymer particle has a diameter D.sub.90 size of 90 to 180
.mu.m before plasma spraying.
12. A prepreg for automated tape laying of in situ thermoplastic
fiber reinforced composite materials comprising: a thermoplastic
fiber reinforced composite material having a first surface and a
second surface; and a thermoplastic surface layer polymer on at
least the first surface.
13. The prepreg according to claim 12, wherein the prepreg
comprises a thermoplastic surface layer polymer on the first
surface and the second surface.
14. A method for preparing a mold tool able to accept a first ply
laydown of thermoplastic fiber reinforced composite material for
automated tape laying of in situ thermoplastic composite materials
comprising: providing a non-porous metal mold tool having a mold
surface; applying a texture to the mold surface of the mold tool;
applying a release film to the texture on the mold surface of the
mold tool; introducing a plurality of thermoplastic surface layer
polymer particles to a plasma spray gun; and plasma spraying the
thermoplastic surface layer polymer particles onto the release film
on the mold tool during in situ tape laydown of a thermoplastic
fiber reinforced composite material.
15. The method for preparing a mold tool according to claim 14
wherein the thermoplastic surface layer polymer particles
introduced to the plasma spray gun is PEKK particles having a
diameter D.sub.90 size of 90-180 .mu.m before plasma spraying.
16. The method for preparing a mold tool according to claim 14
further comprising applying heat to the molding tool after
application of the thermoplastic surface layer polymer to anneal or
crystallize the thermoplastic surface layer polymer.
17. A method of automated tape laying of in situ thermoplastic
fiber reinforced composite material comprising: providing a
non-porous mold tool having a mold surface; applying a release film
to the mold surface of the mold tool; introducing a plurality of
thermoplastic surface layer polymer particles to a plasma spray
gun; plasma spraying the thermoplastic surface layer polymer
particles on the release film to form a thermoplastic surface layer
polymer coating on the mold tool during in situ tape laydown of a
first layer of thermoplastic fiber reinforced composite material
having a first surface in contact with the thermoplastic surface
layer polymer coating and a second surface; plasma spraying the
thermoplastic surface layer polymer particles on the second surface
of the first layer of thermoplastic fiber reinforced composite
materials during the in-situ tape laydown of a subsequent layer of
thermoplastic fiber reinforced composite material having a first
surface and a second surface to form a thermoplastic polymer
interlaminar layer between the second surface of the first layer of
thermoplastic fiber reinforced composite material and the first
surface of the subsequent layer of thermoplastic fiber reinforced
composite material; and continued plasma spraying of thermoplastic
surface layer polymer particles on the subsequent layer of
thermoplastic fiber reinforced composite materials during the in
situ tape laydown until desired number of layers of thermoplastic
fiber reinforced composite material are applied to form a
thermoplastic polymer interlaminar layer between each layer of
thermoplastic fiber reinforced composite material.
18. A thermoplastic fiber reinforced composite part created using a
mold tool according to claim 1, wherein the resulting thermoplastic
fiber reinforced composite part has enhanced surface
properties.
19. The thermoplastic fiber reinforced composite part of claim 18
wherein the enhanced surface property is electrical conductivity.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The subject matter of the present invention relates to fiber
reinforced thermoplastic plastic composite materials and
particularly to applying a surface layer polymer coating to a
composite forming mold tool or to a fiber reinforced thermoplastic
prepreg composite material to enhance the first ply laydown of the
prepreg onto the composite forming mold tool for prepreg forming or
in situ automated laydown tape placement. In situ application of
the surface layer polymer coating during or before automated
laydown may also provide a beneficial resin rich interlaminar layer
between each layer of fiber reinforced thermoplastic composite
material. The surface layer polymer coating is preferably
thermoplastic particles applied by plasma spraying to the mold tool
or prepreg to form a substantially fused layer of thermoplastic
particles. More particularly, in certain embodiments the present
invention relates to layered fiber reinforced thermoplastic prepreg
for use in rapid lamination and forming processes where such fiber
reinforced thermoplastic prepreg are useful in aerospace and other
high-performance automotive/industrial applications.
[0003] 2. Description of the Related Art
[0004] Reinforced thermoplastic and thermoset materials have wide
application in, for example, the aerospace, automotive,
industrial/chemical, and sporting goods industries. Thermosetting
resins are impregnated into the fiber reinforcing material before
curing, while the resinous materials are low in viscosity.
Thermoset composites suffer from disadvantages including processing
problems concerned with removing entrained air or volatiles so that
a void-free matrix is produced. Thermoset composites made by the
prepreg method require lengthy cure times with alternating
pressures to control the flow of the resin as it cures to prevent
bubbles in the matrix. While traditional fabrication of structures
utilized hand placement of thermosetting prepreg plies onto a tool,
current fabrication of large structures utilize robotic placement
of the thermoset composite material onto the tool to increase
production rate. The overall production rate for a structural
component is limited by the lengthy cure in the autoclave process
step and related operations to prepare the material for that
process step. Some high volume processes, such as resin infusion
avoid the prepreg step but still require special equipment and
materials along with constant monitoring of the process over the
length of the cure time (e.g., U.S. Pat. Nos. 4,132,755, and
5,721,034).
[0005] Thermoplastic resin compositions are more difficult to
impregnate into the fiber reinforcing material because of their
comparatively higher viscosity than thermosetting resin
compositions. On the other hand, thermoplastic resin compositions
offer a number of benefits over thermosetting resin compositions.
For example, thermoplastic prepregs can be more rapidly fabricated
into articles and fabrication with fiber reinforced thermoplastic
composite materials may utilize robotic automated laydown tape
placement of the fiber reinforced thermoplastic composite material
onto a mold tool to increase production rate. This may be through a
multiple-step robotic arm that pre-heats the prior layer of fiber
reinforced thermoplastic composite material before heating and
laying the subsequent layer of fiber reinforced thermoplastic
composite material on top of it.
[0006] Thermoplastic resins are long chain polymers of high
molecular weight that are highly viscous when melted and are often
non-Newtonian in their flow behavior. Thus, whereas thermosets have
viscosities in the range of 100 to 5,000 centipoise (0.1 to 5
Pa*s), thermoplastics have melt viscosities ranging from 5,000 to
20,000,000 centipoise (5 to 20,000 Pa*s), and more typically from
20,000 to 1,000,000 centipoise (20 to 1000 Pa*s). Despite a
viscosity difference of three orders of magnitude between
thermosets and thermoplastics, some processes have been applied to
both types of matrices for laminating fibrous materials.
[0007] Fiber reinforced plastic materials may be manufactured by
first impregnating the fiber reinforcement with resin to form a
prepreg, then consolidating two or more prepregs into a laminate,
optionally with additional forming steps. A few processes apply
melt directly to the fibers. A tape can be made by coating a dry
web of collimated fibers with the polymer and applying a heated
process that forces the polymer into and around the fibers (e.g.,
see U.S. Pat. Nos. 4,549,920 and 4,559,262). Another process used
to coat and impregnate a dry web of collimated fibers is by pulling
the web through an aqueous slurry of fine thermoplastic polymer
particles whereby the polymer particles are trapped within the
filament bundles. Subsequent heat and pressure in the process boils
off the water and then melts the polymer to force it into and
around the filament bundles. This process is described in U.S. Pat.
Nos. 6,372,294, 5,725,710, 4,883,552 and 4,792,481. A modification
to the aqueous slurry impregnation process is to eliminate the use
of water and surfactant as dispersing agents for the polymer
particles and instead electrostatically charge the particles in a
fluidized bed of air to trap the particles in the filament bundle.
Subsequent zones of heat and pressure melt the polymer to
coat/impregnate the filament bundle as given in U.S. Pat. No.
5,094,883. Thus, for those skilled in the art, there are multiple
methods to coat and/or impregnate a fibrous substrate given the
available process equipment, and proper selection of polymer
product form (flake, fine powder, film, non-woven veil, pellets)
and melt viscosity.
[0008] Both thermoplastic and thermoset composites can be formed
into thin flexible sheets or strips, referred to as tape. This
allows composite components to be formed by laying down the
composite tape in a molding tool, with the thickness of the
component being locally varied according to the number of layers of
composite tape laid down and also the direction of one or more
layers of the tape being controllable so as to control the final
structural properties of the formed composite component. The laid
up components are then "consolidated", a process which cases
involves heating the composite structure so that the thermoset or
thermoplastic matrix softens to a sufficient degree to form a
single unified matrix, and applying sufficient pressure to the
softened matrix to expel any trapped air from the matrix.
[0009] In terms of final structural properties, thermoplastic
composites have superior impact and damage resistance properties to
those of thermoset composites and are generally tougher and more
resistant to chemical attack, all of which are preferable
properties within aerospace applications. Furthermore, since
thermoplastic composites may be repeatedly reheated and remolded,
they are inherently recyclable, which is an increasingly important
consideration.
[0010] However, thermoset composite tape has one property that, in
relation to the laying up process, currently makes it the material
of choice for use in aerospace composite components. This property
is that the thermoset tape is inherently sticky, or is said to have
tack. This tackiness allows the thermoset tape to adhere to both
the complex shaped mold surfaces often required for composite
components within the aerospace industry, and also for separate
layers of the thermoset tape to adhere to one another once the
initial layer has been applied to the mold surface, thus making the
laying up process relatively easy and convenient to physically
manage.
[0011] In contrast, thermoplastic composite tape has no tackiness.
Consequently, it is problematic to make the thermoplastic composite
tape adhere to complex mold surfaces during the lay-up process.
Existing lay-up techniques combine local consolidation and melting
of the thermoplastic composite material to enable the initial, base
layer to be built up only as long as the base layer is firmly held
to the surface of the mold tool. Previously proposed solutions to
this problem have included applying a separate double-sided
adhesive tape as an initial layer to the mold surface to which the
first layer of thermoplastic composite tape subsequently adheres.
Similarly, it has also been proposed to spray an adhesive to the
surface of the mold. Whilst both proposed solutions allow the first
layer of thermoplastic composite tape to be successfully applied to
complex shaped mold surfaces, they introduce their own problem of
how to subsequently remove the formed composite component from the
mold when the laying up process is complete, since the component is
now effectively bonded to the mold surface. Consequently, it is
still presently preferred to use thermoset composite materials
despite the superior physical properties provided by thermoplastic
composite materials.
[0012] Known methods for fabrication of composite articles include
manual and automated fabrication. Manual fabrication entails manual
cutting and placement of material by a technician to a surface of
the mandrel. This method of fabrication is time consuming and cost
intensive, and can possibly result in non-uniformity in the
lay-up.
[0013] Automated fabrication techniques include flat tape
laminating machines (FTLM) and contour tape laminating machines
(CTLM). Typically, both FTLM and CTLM employ a solitary composite
material dispenser that travels over the work surface onto which
the composite material is to be applied. The composite material is
typically laid down a single row (of composite material) at a time
to create a layer of a desired width and length. Additional layers
may thereafter be built up onto a prior layer to provide the lay-up
with a desired thickness. FTLM's typically apply composite material
to a flat transfer sheet; the transfer sheet and lay-up are
subsequently removed from the FTLM and placed onto a tool, mold or
mandrel. In contrast, CTLM's typically apply composite material
directly to the work surface of a tool, mold or mandrel. FLTM and
CTLM machines are also known as automated tape laydown (ATL) and
automated fiber placement (AFP) machines, with the dispenser
commonly referred to as a tape head.
[0014] The productivity of ATL/AFP machines is dependent on machine
parameters, composite part lay-up features, and material
characteristics. Machine parameters such as start/stop time, course
transition time, and cut/adding plies determine the total time the
tape head on the ATL/AFP is laying material on the mandrel.
Composite lay-up features such as localized ply build-ups and part
dimensions also influence the total productivity of the ATL/AFP
machines.
[0015] The ideal process for creating thermoplastic parts is in
situ fabrication wherein a part is created by robotically placing
and consolidating thermoplastic materials onto the molding tool in
one step. Thermoplastic composite materials lack tack, which
complicates the use of hand and automated lay-up operations,
especially of the first ply against the molding tool surface.
[0016] Key material factors that influence ATL/AFP machine
productivity are similar for a thermoset resin matrix composite
when compared with a thermoplastic matrix composite yet there are a
couple of key differences. For thermoset resin matrix composites,
key factors are impregnation levels, surface resin coverage, and
"tack". Tack is the adhesion level necessary to maintain the
position of the tape/tow on the tool or lay-up after it has been
deposited on it. Due to the unreacted nature of the thermoset
resin, the ATL/AFP process is generally performed at room
temperature but in humidity controlled rooms due to the moisture
sensitivity on the tack level of the material. Among other impacts,
tack affects the ability to lay down the first ply of material onto
the tool. First ply lay-down of thermoplastic materials is
complicated by the lack of tack to hold the first layer down to the
tool.
[0017] The first composite ply to be placed against any tool
requires some adhesive or other force to position the material and
hold it against gravity or the stiffness of the material. When
thermoset materials are used, the polymer that is above the T.sub.g
at the lay-down head will provide this force. When the matrix resin
is a high performance thermoplastic, this T.sub.g temperature is
substantially higher and substantially above room temperature.
Heating the mold tool, providing a vacuum source, use of a lower
temperature film or using a solvated thermoplastic polymer to
provide the restraining force are all methods currently used. Each
of these methods has limitations in cost, tool complexity,
variation to the dimensions of the part or requires hazardous
solvents to practice.
[0018] A method known to overcome the limitation of low tack in
thermoplastics manufacturing is to provide a mold tool made of a
porous material and apply a negative pressure to the porous
material so as to create a negative pressure at the mold surface,
whereby the thermoplastic composite material is held against the
mold surface by virtue of the negative pressure at the mold surface
when the initial layer of thermoplastic composite material is laid
onto the mold surface. The thermoplastic material could thereafter
be consolidated and heated to form the thermoplastic composite
material (see, e.g., U.S. Patent Application Publication No.
2011/0005666).
[0019] Thermoplastic matrix composites have similar key factors as
thermoset matrix composites for ATL/AFP machine productivity, but
the thermoplastics polymer tape lack tack at ambient conditions.
Thermoplastics generally have low surface energies, a high glass
transition temperature ("T.sub.g"), making adhesion at room
temperature unlikely. Furthermore, the high performance
thermoplastic matrices are in their glass state at room temperature
making the molecular diffusion mechanism for tack virtually
impossible. Thus, tack is achieved in thermoplastic composites by
dynamically applying additional energy in the form of thermal,
ultrasonic, optical (laser), and/or electromagnetic (induction) to
the lay-up and incoming tape to raise the temperature of the
materials above their softening and/or melt temperature in order to
facilitate molecular diffusion of the polymer chains to occur
between the two surfaces. Once the polymer chains have diffused
across the surface, the additional energy added to the materials
needs to be removed to a level that will prevent distortion of the
laminated lay-up once the lamination pressure from the ATL/AFP head
is removed. This rapid flux of energy into and out of the lay-up
makes it desirable from an energy usage and lay down speed to
perform this process step at the lowest possible temperature and
energy without compromising on the temperature performance of the
resulting composite part.
[0020] Consolidation is typically necessary to remove voids that
result from the inability of the resin to fully displace air from
the fiber bundle, tow, or roving during the processes that have
been used to impregnate the fibers with resin. The individually
impregnated roving yarns, tows, plies, or layers of prepregs are
usually consolidated by heat and pressure by compacting in an
autoclave. The consolidation step has generally required the
application of very high pressures and high temperatures under
vacuum for relatively long times. Furthermore, the consolidation
process step using an autoclave or oven requires a "bagging"
operation to provide the lay-up with a sealed membrane over the
tool to allow a vacuum to be applied for removal of air and to
provide the pressure differential necessary to effect consolidation
in the autoclave. This process step further reduces the total
productivity of the composite part operation. Thus, for a
thermoplastic composite it would be advantageous to in-situ
consolidate to a low void composite while laminating the tape to
the substrate with the ATL/AFP machine. This process is typically
referred to as in situ ATL/AFP and the material used in that
process called an in situ grade tape.
[0021] In general, thermoplastic composites have had limited
success to date, due to a variety of factors including high
processing temperatures (currently around 400.degree. C.), high
pressures, and prolonged molding times needed to produce good
quality laminates. Most of the efforts have been focused on
combining high performance polymers to structural fibers which has
only exacerbated the process problems. Because the length of time
typically required to properly consolidate the prepreg plies
determines the production rate for the part, it would be desirable
to achieve the best consolidation in the shortest amount of time.
Moreover, lower consolidation pressures or temperatures and shorter
consolidation times will result in a less expensive production
process due to lowered consumption of energy per piece for molding
and other manufacturing benefits.
[0022] Accordingly, the fiber-reinforced thermoplastic materials
and methods presently available for producing light-weight,
toughened composites require further improvement. Thermoplastic
materials having improved process speeds on automated lay-up
machines and lower processing temperatures and having no autoclave
or oven step would be a useful advance in the art and could find
rapid acceptance in the aerospace and high-performance automotive
industries, among others.
SUMMARY OF THE INVENTION
[0023] The present invention provides a prepared mold tool having a
releasably adhered surface layer polymer coating on the mold
surface of the mold tool. The mold tool is a non-porous metal mold
tool having a mold surface with a texture and a release film
adhered to the textured mold surface of the mold tool and the
surface layer polymer coating adhered to the release film. The
surface layer polymer coating is preferably a plurality of
thermoplastic particles applied to the mold surface by plasma spray
creating a substantially fused layer of thermoplastic particles.
The prepared mold tool aids placement and adhesion of the first ply
of a fiber reinforced thermoplastic composite material such as a
thermoplastic prepreg, a thermoplastic unidirectional tape or web,
fiber tow/preg, or fabric, or non-woven materials such as a mat or
veil. Thermoplastic prepregs are traditionally applied by hand
lay-down while thermoplastic unidirectional tapes are applied by in
situ automated laydown tape placement against a mold tool.
[0024] The present invention also involves a method for preparing a
prepared mold tool for first ply laydown by providing a solid
metal, non-porous mold tool having a mold surface, applying a
texture to a mold surface of the mold tool, applying a release film
to the mold surface having a texture and finally applying a surface
layer polymer coating by plasma spraying thermoplastic particles
onto the release film on the mold surface of the mold tool having
the texture.
[0025] A further embodiment of the present invention provides a
prepared prepreg having fiber reinforced thermoplastic composite
material with a surface layer polymer coating adhered to one or
both surfaces of the composite material. The surface layer polymer
coating is preferably a plurality of thermoplastic particles
applied to the surface of the fiber reinforced thermoplastic
composite materials by plasma spray to create a substantially fused
layer of thermoplastic particles on the surface. The prepared
prepreg aids placement of the first ply of fiber reinforced
thermoplastic composite material to a mold surface of a mold tool
and may further improve resulting composite part interlaminar
properties between plies of composite material.
[0026] The present invention also involves a method for preparing
the prepared prepreg by providing a fiber reinforced thermoplastic
composite material such as a thermoplastic prepreg or a
thermoplastic unidirectional tape and then applying a surface layer
polymer coating by plasma spraying thermoplastic particles onto one
or both of the surfaces of the fiber reinforced thermoplastic
composite material.
[0027] In the present invention, the surface layer polymer coating
provides a compatible chemistry placed against the mold tool which
maintains the dimensions, lowers the temperature requirement for
adhesion, and allows the use of hybrid polymer and optional
inclusion of conductive coatings for lightning strike in the
surface layer polymer coating. This compatible chemistry of the
present invention improves adhesion of the first ply of fiber
reinforced thermoplastic composite material to the mold surface of
the mold tool while maintaining ease of separation of the resulting
composite part from the mold tool. When the resulting composite
part is removed from the mold tool, the surface layer polymer
coating will transfer to the resulting composite part as a surface
skin that may impart desirable characteristics to the resulting
composite part. Such desirable characteristics such as fire,
corrosion or wear protection may come from multi-functional
additives to the surface layer polymer coating.
[0028] Of particular importance is where the surface layer polymer
coating is a high performance thermoplastic such as poly(ether
ether ketone) ("PEEK") or poly(ether ketone ketone) ("PEKK").
[0029] The present invention seeks to improve first-ply lay-down by
reducing composite part failure due to material de-bonding against
the mold tool during processing, as well as improving chemical
compatibility in the high performance thermoplastic polymer.
Concepts including fast crystallization or amorphous materials as
well as discrete metallic layers and ground fiber mixtures are
possible. Furthermore, this discovery also reduces the initial
capital and facility cost investment to produce large
composites.
[0030] The present invention also provides methods for
manufacturing a resulting thermoplastic composite part with a
thickness in the range of 25 to 400 microns that has improved
processing times on ATL machines and manufacturing equipment.
[0031] Accordingly, the invention described in detail herein
provides, in one aspect, a prepared mold tool having a surface
layer polymer coating of at least one high performance polymer, and
a prepared prepreg having surface layer polymer coating on one or
both surfaces.
[0032] In another aspect, the invention relates to articles of
manufacture made from the thermoplastic composites according to the
invention described herein. Such articles are useful, for example,
in the aircraft/aerospace industries among others.
[0033] In situ grade thermoplastic composite material tapes for use
on an automated tape laydown or automated fiber placement machine
are also provided.
[0034] These and other features and advantages of this invention
will become apparent from the following detailed description of the
various aspects of the invention taken in conjunction with the
accompanying Figures and Examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1a is a side plan view of one embodiment of the present
invention illustrating the configuration of the prepared tool (10)
including the non-porous metal mold tool (20), the textured mold
surface (30) of the mold tool, the release film (40) and the
surface layer polymer coating (50).
[0036] FIG. 1b is a perspective view of the embodiment of FIG. 1a
illustrating the configuration of the prepared tool (10) including
the non-porous metal mold tool (20), the textured mold surface (30)
of the mold tool, a sealer and the applied release film (40) and
the surface layer polymer coating (50) shown as substantially fused
thermoplastic particles after application by plasma spraying.
[0037] FIG. 2a illustrates a perspective view of in situ
application of the surface layer polymer coating (50) from a plasma
spray head (70) onto a non-porous metal tool (20) followed by
application of a first ply thermoplastic fiber reinforced composite
material (60) and compacted by an AFP/ATL laydown roller (80).
[0038] FIG. 2b further illustrates a perspective view of in situ
application of the thermoplastic interlaminar layer (90) (e.g.,
thermoplastic particles) from a plasma spray head (70) onto a
previously applied thermoplastic composite tape material (60)
followed by application of a subsequent ply thermoplastic fiber
reinforced composite material (60) and compacted by an ATL laydown
roller (80) providing in situ applied thermoplastic interlaminar
layer (90) between layers of thermoplastic fiber reinforced
composite material during automated tape lay-down.
[0039] FIG. 3 illustrates a side plan view of a surface layer
polymer coating applied to a thermoplastic composite prepreg by
plasma spraying a thermoplastic polymer coating (50) from a plasma
spray head (70) onto one or both surfaces of a composite material
(60) to form a plasma coated thermoplastic composite material
(100).
[0040] FIG. 4a illustrates the mean spacing of local peaks of
profile of a high temperature mold tool and a thermoplastic surface
layer polymer coating using a profilometer.
[0041] FIG. 4b illustrates the spacing of peaks in the y-axis.
DETAILED DESCRIPTION OF THE INVENTION
[0042] The present invention provides a prepared mold tool having a
surface layer polymer coating applied to the release side mold
surface of the mold tool to enhance adhesion of the first ply of
thermoplastic fiber reinforced composite material to the mold
surface.
[0043] FIG. 1a illustrates such an embodiment of the present
invention providing the configuration of a prepared tool (10),
including the non-porous metal mold tool (20) with a textured
molding surface (30), a release film (40) and a surface layer
polymer coating (50) releasably applied to the release film. FIG.
1b illustrates such an embodiment of the present invention
providing the prepared tool (10) detailing the surface layer
polymer coating (50) shown as substantially fused thermoplastic
particles applied by plasma spraying.
[0044] Importantly, surface layer polymer coating (50) may be
applied to the release side mold surface of mold tool (20) through
use of plasma spray during in situ automated tape laydown.
Continued plasma spray of the surface layer polymer during
automated tape laydown on top of a prior ply of fiber reinforced
composite material (60) provides a thermoplastic interlaminar layer
(90) that can impart beneficial properties such as toughening to
the resulting composite part.
[0045] FIG. 2a illustrates in situ application of the surface layer
polymer coating (50) such as thermoplastic particles from a plasma
spray head (70) onto a non-porous metal mold tool (20) and then the
application of thermoplastic fiber reinforced composite material
(60) and compacted by an ATL laydown roller (80).
[0046] FIG. 2b further illustrates continued plasma spray of the
surface layer polymer by plasma spray head (70) during automated
tape laydown thereby providing a thermoplastic interlaminar layer
(90), and then application of a subsequent ply of thermoplastic
fiber reinforced composite material (60) compacted by ATL laydown
roller (80). Continued application of the surface layer polymer
coating such as a thermoplastic from a plasma spray head (70) onto
a previously ply of thermoplastic fiber reinforced composite
material (60) and then a subsequent ply of thermoplastic composite
material (60) applied and compacted by an ATL laydown roller (80)
provides an in situ applied interlaminar thermoplastic layer (90)
between the layers of thermoplastic fiber reinforced composite
material and subsequently applied thermoplastic fiber reinforced
composite material during automated tape lay-down.
[0047] Thermoplastic interlaminar layer (90) and surface layer
polymer coating (50) are each high performance thermoplastic
polymers, and may be the same or different materials and may
contain the same or different multifunctional additives. This
versatility in selection of the particular high performance
thermoplastic polymer permits selection of the optimal materials
for the surface layer coating (50) and the interlaminar layer
(90).
[0048] Similarly, the first ply fiber reinforced composite material
(60) and the subsequent plies of fiber reinforced composite
material (60) are each compatible material, but may be the same or
different compositions depending upon the properties desired for
each layer.
[0049] Alternatively, the present invention provides prepared
prepreg having a surface layer polymer coating applied directly to
one or more surfaces of a thermoplastic fiber reinforced composite
prepreg material to enhance adhesion of the first ply of the
thermoplastic fiber reinforced composite material to the mold
surface of the mold tool and to further provide a beneficial
interlaminar layer to the resulting composite part.
[0050] FIG. 3 illustrates a prepreg (100) prepared by applying a
surface layer polymer coating (50) to both surfaces of a
thermoplastic fiber reinforced composite material (60) by plasma
spraying thermoplastic particles from a plasma spray head (70) onto
the surfaces of a fiber reinforced composite material (60), thereby
forming the prepared prepreg (100). Depending upon the performance
of the resulting composite part sought, the surface layer polymer
coating may be the same or different on each side of the prepared
prepreg (100).
[0051] Prepared tool (10) of the present invention incorporates a
surface layer polymer coating (50) that is releasably adhered to
the mold surface of a mold tool (20). Preferably, a release film
(40) is interposed between the mold surface of the mold tool (20)
and the surface layer polymer coating (50). Additionally, for
optimal control of adhesion of the surface layer polymer coating
(50) to the mold surface, the mold surface of the mold tool (20) is
a textured surface (30). Prepared tool (10) may be utilized for
laydown of fiber reinforced composite material by hand or by ATL as
may be desired. Prepared tool (10) provides optimal controlled
adhesion of the first ply fiber reinforced composite material
during either hand or ATL application.
[0052] FIG. 2a illustrates laydown of a first ply fiber reinforced
composite material (60) by automated tape laydown placement onto
the mold surface of mold tool (20). When using a tape prepreg as
the fiber reinforced composite material (60), a plasma spray head
(70) will spray thermoplastic particles onto the mold surface,
forming the surface layer polymer coating (50) on the mold surface
for preparation of the mold surface of mold tool (20).
Subsequently, an ATL laydown roller (80) lays down and releasably
adheres the tape prepreg fiber reinforced composite material (60)
onto the surface layer polymer coating (50) on the mold surface of
the mold tool (20). Continued application of this process is
illustrated by FIG. 2b wherein subsequent layers of fiber
reinforced composite material (60) are applied by spraying
thermoplastic particles onto the surface of a previously adhered
layer of fiber reinforced composite material (60) using a plasma
spray head (70), and then applying with the ATL laydown roller (80)
a subsequent ply of fiber reinforced composite material to create a
thermoplastic interlaminar layer (90). This thermoplastic
interlaminar layer (90) can provide beneficial toughening or other
multifunctional benefits as desired.
[0053] Prepreg (100) of the present invention is prepared by
applying a surface layer polymer coating (50) to one or both
surfaces of a fiber reinforced composite material (60) directly
before or during in situ laydown of the fiber reinforced composite
material (60). A flow of fiber reinforced composite material (60)
is passed between one or more plasma spray heads (70) that apply
surface layer polymer coating (50) to one or both sides of the
composite material (60), thereby forming the prepared prepreg
(100). This prepared prepreg (100) can then be directly applied to
a mold tool or a prepared tool (10) by hand laydown or by ATL as
desired, and is releasably adhered to the mold surface of the mold
tool or prepared tool (10). Prepared prepreg (100) can be applied
as a tape prepreg by an ATL laydown roller as shown in FIG. 2a,
without the need for a separate plasma spray head (70) for applying
a first ply of fiber reinforced composite material having a surface
layer polymer coating (50) adjacent to the mold surface of the mold
tool (20). The mold surface is preferably a textured mold surface
(30). Prepared prepreg (100) can save manufacturing costs and
create more uniform manufacturing conditions while providing the
same potential multifunctional benefits. If the surface layer
polymer coating (50) is applied to both surfaces of a fiber
reinforced composite material (60), the coating (50) on each
surface can have the same or different compositions.
[0054] Various methods of applying surface layer polymer coating
(50) are available and known in the art, such as by spraying a
solvent based polymer solution onto the mold surface of a metal
mold tool, by hand applying a water based slurry, by a plasma spray
application, or an electrostatic powder coating and fusing method,
among others.
[0055] One particularly preferred embodiment of the present
invention provides for plasma spray application of the surface
layer polymer onto the mold surface of a mold tool (20) forming a
prepared tool (10) as illustrated in FIGS. 1a and 1b, or directly
onto the fiber reinforced composite material (60) as depicted in
FIG. 3 to form prepared prepreg (100). When the surface layer
polymer coating (50) is applied using a plasma spray gun, the
surface layer polymer is introduced to the plasma gun in the form
of solid particles, preferably thermoplastic particles with a
D.sub.90 diameter (wherein ninety percent of the particles are
smaller than the number, by volume) from 90 to 180 .mu.m and more
preferably from 150 to 185 .mu.m. The particles are applied using a
low velocity, high temperature plasma.
[0056] A preferred high performance polymer surface layer polymer
particle is PEEK polymer.
[0057] Surface layer polymer coating (50) is substantially
continuous, but may be discontinuous at lower thickness levels
along the mold surface, especially depending upon the level of
roughness of textured surface (30) to which it is applied. It is
desired to be continuous over at least 50% of the mold surface, and
more preferably at least 90% of the mold surface and optimally, at
least 98% of the mold surface. When utilizing a plasma spray head
(70) to apply the surface layer polymer coating (50), the heated
thermoplastic particles impact and adhere to the mold surface as
molten particles and the resulting surface layer coating (50) can
appear as a discontinuous plurality of beads that are well fused
thermoplastic particles, but not all are melt fused together,
forming the partially discontinuous film.
[0058] The high performance polymer particle size is D.sub.90 of
about 100 .mu.m to about 400 .mu.m. Preferably, the polymer
particle sizes is in the D.sub.90 range of from about 125 .mu.m to
about 250 .mu.m, and most preferably from about 150 to about 200
.mu.m for optimum plasma spray application results. When applied,
the high performance polymer particles are exposed to a plasma
spray head temperature in the range of about 1800.degree. F. to
about 2000.degree. F. at a velocity of about 350 to about 400
.mu.m/second at the vent port nozzle section of the plasma spray
applicator.
[0059] Useful commercially available plasma spray applicator
include the Praxair SG 10 plasma spray applicator or a Sulzer Metco
plasma spray applicator. The high performance polymer is introduced
into the plasma spray head as a solid particle. The plasma spray
applicator then directs the solid particles into the plasma jet
stream to heat and accelerate the particles to a high velocity.
[0060] For best performance, the mold tool (20) is pre-heated to
about 250.degree. F. (121.degree. C.) to aid in adhering the
surface layer polymer coating (50) to the mold surface of the mold
tool (20).
[0061] For preparation of a prepared mold tool, plasma spraying
should apply surface layer polymer coating (50) to the mold surface
of the mold tool (20) at a thickness in the range from 0.001 to
0.010 inch thick layer. In some embodiments, the thickness of the
surface layer polymer coating (50) is more preferably about 0.002
inches. This thickness is intended to aid in adhesion of the first
ply without adding significant weight to the resulting composite
part.
[0062] In preparing a prepared prepreg (100), plasma spraying
should apply a surface layer polymer coating (50) onto a fiber
reinforced thermoplastic composite material (60) at a thickness of
from about 0.0005 to about 0.010 inches per layer. In some
embodiments, the thickness of the surface layer polymer can be from
about 0.001 to about 0.008 inches per layer.
[0063] Surface layer polymer coating (50) can be releasably applied
to the mold surface of mold tool (20) to allow effective release of
the resulting composite part from the mold surface of the mold
tool. While a difficulty with automated tape lay-down of
thermoplastic fiber reinforced composite materials is ineffective
adhesion of the first ply to the mold surface of the mold tool, the
thermoplastic surface layer polymer coating should not adhere so
strongly to the mold surface of the mold tool so that when removal
is attempted, the thermoplastic surface layer polymer coating is
compromised and the resulting thermoplastic composite part is
damaged. This is especially important when the thermoplastic
surface layer polymer coating contains any multi-functional agent
such as described herein to further enhance the surface properties
of the resulting thermoplastic composite part.
[0064] For purposes of this invention, the thermoplastic surface
layer polymer coating is said to be releasably applied when the
resulting thermoplastic composite part made on a mold tool with a
thermoplastic surface layer polymer coating releases from the mold
tool with slight to modest pressure, while the surface layer
polymer coating does not detach during the automated in situ
laydown of the thermoplastic fiber reinforced composite
material.
[0065] The thermoplastic surface layer polymer (50) on the mold
surface of mold tool (20) can improve the surface quality and
properties of the resulting thermoplastic composite part once it is
removed from the mold tool due to the qualities of the resin rich
thermoplastic surface layer polymer coating, the enhanced surface
texture, and optional multi-functional additives which can be
incorporated therein.
[0066] The surface layer polymer coating (50) can comprise a high
performance polymer chosen from a slow crystallizing,
semi-crystalline polymer or an amorphous polymer (or mixtures
thereof), such that the thermoplastic surface layer polymer coating
(50) forms a miscible and/or compatible blend with the high
performance thermoplastic polymer of the fiber reinforced
thermoplastic composite material (60). The surface layer polymer
coating (50) can be any one of the high performance thermoplastic
polymers described herein that is applied to the mold surface of
mold tool (20) for improved processing of first ply laydown as
described herein or applied directly to one or both surfaces of
thermoplastic fiber reinforced composite material (60) before
application to the mold tool.
[0067] The morphology of the high performance thermoplastic polymer
can be amorphous and/or a slow crystallizing (i.e., low
crystallinity--typically less than 20% crystallinity)
semi-crystalline polymer. Blends of amorphous and semi-crystalline
polymers are also contemplated for use as the surface layer polymer
coating (50). In certain embodiments, the high performance
thermoplastic polymer for thermoplastic surface layer polymer
coating (50) is chosen from polyaryletherketones (PAEK),
polyetherimide (PEI), polyimides, PAEK co-polymer with PEI and/or
polyethersulfone (PES) and/or polyphenylenesulfide (PPS), and PAEK
blends with one or more of PEI, PES, PPS and/or polyimides.
[0068] In particular embodiments, for example, thermoplastic
surface layer polymer coating includes PAEK chosen from
polyetheretherketone (PEEK) or polyetherketoneketone (PEKK) and
blends with, such as, but not limited to, diphenylsulfone. When the
thermoplastic surface layer polymer includes PEKK, the T:I ratio of
the PEKK ranges from about 0:100 to about 70:30 in order to
maintain the slow crystallization rate of the surface layer
polymer. In a particular embodiment, the T:I ratio of the
thermoplastic surface layer polymer uses CYPEK.RTM. DS that has a
T:I ratio of from about 0:100 to about 70:30. Suitable PEKK
polymers available for use with the present invention include, but
are not limited those commercially available from Cytec Industries
Inc., Woodland Park N.J., such as CYPEK.RTM. DS-E or CYPEK.RTM.
DS-M and CYPEK.RTM. HT.
[0069] The surface layer polymer coating (50) can further include
one or more multi-functional agents chosen for improving the
resulting thermoplastic composite part features, such as electrical
conductivity, toughness, oxygen permeability, crystallization rate
and/or solvent resistance of the resulting thermoplastic composite
part. Such multi-functional agents may be in the form of a metallic
coating and/or micro- and/or nano-particles.
[0070] The optional surface layer polymer coating (50)
multi-functional agents can include one or more of materials such
as, but not limited to, impact modifiers, mold release agents,
lubricants, thixotropes, antioxidants, UV absorbers, heat
stabilizers, flame retardants, pigments, colorants, layered
colorants for impact damage indicators, nonfibrous reinforcements
and fillers, nano-graphite platelets, to enhance crystallinity rate
and mitigate shrinkage, nano-clays to improve solvent resistance,
nano-metals (such as nickel fibrils), particle interleaving for
impact toughening, CVD veil fabrics in interleave for OML lightning
strike, fiber or polymer veils to improve impact performance,
surface finishes to aid in air removal as the pressure is applied
by the ATL machine, and high flow surface coatings to speed
reptation healing across the inter-ply region.
[0071] The mold tool (20) can be of any non-porous high temperature
tooling including metal. Metal tooling, preferably stainless steel,
invar or low carbon steel as known to one skilled in the art are
all appropriate. The mold surface of the mold tool (20) can be
stainless steel able to withstand the high processing temperatures
required for thermoplastic fiber reinforced composite part
manufacturing and low CTE, but is preferably invar. High
temperature tooling is capable of withstanding processing
temperatures up to 800.degree. F. (427.degree. C.). Mold tool (20)
can be a 0.120'' thick 304 stainless steel plate or 0.063'' invar
36. However, the stainless steel plate may not be as effective as
invar due to higher differential CTE, which can cause delamination
during processing of the thermoplastic fiber reinforced composite
material from the mold surface of the mold tool.
[0072] The mold tool (20) should be a solid, impermeable material
that is non-porous. The mold tool (20) should not allow the flow of
air or gases through its mold surface.
[0073] A textured mold surface (30) is preferably created on the
mold surface of the mold tool (20) in order to improve mechanical
adhesion of the surface layer polymer (50) to the mold tool (20) in
an effort to overcome the CTE differential delaminating the
thermoplastic fiber reinforced composite material (60) and surface
layer polymer coating (50) from the mold surface of mold tool (20).
The textured mold surface (30) is believed to provide a mechanical
interlock between the mold tool (20) and the surface layer polymer
coating (50), as well as improve adhesion in order to overcome
differences in coefficient of thermal expansion between the surface
layer polymer coating (50) and the mold tool (20). Too little
texture and the mechanical interlock will be insufficient to
overcome the CTE differential, resulting in the surface layer
polymer coating (50) easily peeling off of the mold tool (20)
during manufacture. Too course of textured mold surface (30) can
result in a surface layer polymer coating (50) that can be
difficult to release and remove without causing damage to the
surface layer polymer coating (50) when trying to remove the
resulting composite part from the mold tool.
[0074] The textured mold surface (30) cab be added by many means
such as sandblasting, milling, Blanchard grinding, glass bead
blasting, knurling, or other means to texture the mold surface to
accept the release film (40). Creation of the textured mold surface
(30) can be accomplished by a method such as sandblasting with a
grit size from about 20 grit to about 180 grit, and more preferably
40 grit to 120 grit. In particular, about 120 grit aluminum oxide
or about 40-60 grit glass beads provide an even texture on the
surface and are preferred with the 40-60 grit glass beads being
optimal. The preferred methods of applying an appropriate texture
is by sandblasting with 120 grit aluminum oxide or 40-60 grit glass
beads.
[0075] The appropriate texture for a particular combination of mold
surface of a mold tool (20) and surface layer polymer coating (50)
can be optimized by one skilled in the art to identify the most
appropriate level of texture for a particular surface layer polymer
coating (50) and mold tool (20). One skilled in the art will be
able to identify the most appropriate level of texture for the type
of mold tool material and surface layer polymer coating material to
overcome the CTE differences involved to support sufficient
adhesion while maintaining releasability of the resulting composite
part.
[0076] One method of quantifying an appropriate level of texture is
by measuring the profile elements of a textured mold surface (30).
Both a greater mean spacing of profile elements and greater depth
of profile elements are appropriate methods of distinguishing
preferred levels of texture. Both profile elements need to be
appropriate for the texture to be appropriate.
[0077] A high temperature mold tool and a thermoplastic surface
layer polymer coating, a 0.063'' invar 36 sheet with a PEKK surface
layer polymer coating, was tested with a Time Group Inc. TR200
diamond stylus tip surface profilometer, inductance type surface
roughness tester. The surface profilometer uses a diamond stylus
that is moved at a controlled speed over the surface of the sample
to detect characteristics of the material. These parameters are
measured on a flat sample by resting the device on top of the
sample. This is test is performed at standard room temperature and
humidity and the mold tool tested should be at room temperature.
The profilometer is set onto the sample in the x-direction (defined
as parallel to the edge of the test bench) and the test is begun
using the play arrow key and all parameters are recorded for the
X-direction. The profilometer is then repositioned perpendicular to
the previous test and the test is repeated to record all parameters
for the Y-direction.
[0078] This Rsm calculation is illustrated in Formula 1, with
R.sub.Y illustrated in Formula 2. As seen in Table 1 below, a
combination of maximum peak-to-peak measurement profile height was
found to be the best characteristic of optimal texture. Values
greater than those shown in Table 1 may be obtained and used.
However, greater values may adversely increase mechanical adhesion,
impact resulting composite part dimension, and distort
tolerances.
TABLE-US-00001 TABLE 1 (Micro Invar Meters) 36 120 Tool Stainless
120 40-60 Mill grit finish Steel grit 40-60 Glass scale AlO.sub.2
Direction Description Smooth AlO.sub.2 glass X X Y X1 X2 X3 Y Rsm
mean spacing of profile 0.160 0.114 0.093 0.167 0.200 0.182 0.070
0.071 0.068 0.067 elements R.sub.Y Maximum height of 1.391 4.707
7.28 6.255 7.059 6.664 7.288 7.084 7.032 5.947 profile
[0079] The mold release film (40) can be applied to the mold
surface of mold tool (20) after applying textured mold surface (30)
to the mold tool to evenly and uniformly cover the mold surface of
the mold tool (20). The mold release film (40) further provides the
appropriate releasable adhesion of the surface layer polymer
coating (50) to the mold surface of the mold tool (20). The mold
release film (40) may only partially cover the textured mold
surface (30) of the mold tool (20), so long as it covers that
recommended by the mold release manufacturer.
[0080] The mold release film (40) functions as an interface between
the textured mold surface (30) of the mold tool (20) and the
surface layer polymer coating (50). The mold release film (40) also
provides a chemical bonding to restrain the surface layer polymer
coating (50) on the mold surface, thereby maintaining optimal
adhesion and subsequent releasability of the surface layer polymer
coating to the mold surface during application of the thermoplastic
fiber reinforced composite material. The mold release film (40) is
also robust enough to survive the intense heat and conditions from
the laydown process such that it provides a release layer to
separate the surface layer polymer coating (50) from the mold tool
(20) once the resulting composite part has been cured.
[0081] Mold release film materials are commercially available and
are advertised as capable of releasing the product from a mold tool
after processing. Suitable commercial mold release film include
Hysol Frekote 800, AXEL 21RM, AXEL 21LS, and AXEL W-4005. The
release agent is preferably high temperature AXEL W-4005 applied
and seasoned per the manufacturer's specifications.
[0082] The mold tool (20) together with the mold release film (40)
can then be heated to "season" as recommended by the supplier.
[0083] A sealer can optionally be applied to the mold surface of
mold tool (20) as recommended by the mold tool manufacturer prior
to application of the mold release film (40) to further increase
the releasable adhesion of the surface layer polymer coating (50)
and allow release of the resulting composite part from the mold
surface.
[0084] Fiber reinforced composite material (60) are structural
reinforcement fiber materials, pre-impregnated with an appropriate
high performance thermoplastic polymer matrix resin. These are
generally categorized as tape, woven cloth, non-woven cloth, paper,
and mixtures thereof.
[0085] Suitable structural reinforcement fibers for fiber
reinforcement include any of the commercially available structural
fibers such as carbon fibers, Kevlar.RTM. fibers, glass fibers,
aramid fibers, and mixtures thereof. In a preferred embodiment the
fibrous structural reinforcement fiber is a polyacrylonitrile (PAN)
based carbon fiber.
[0086] The fibrous structural reinforcement can be configured in a
unidirectional tape (uni-tape) web, non-woven mat or veil, fiber
tow, or fabric material. Tape prepreg generally refers to
unidirectional structural reinforcement fibers that extend along a
single axis of the strip material. Tape prepreg is generally used
for ATL laydown applications. The term "cloth" generally refers to
structural reinforcement fibers laid along at least two different
axes within the strip material. Cloth is commercially available as
bi-axial, tri-axial and quad-axial, indicating fibers extending in
two, three, or four different axes, respectively. The fibers may
optionally be woven with one another, or may be manufactured as
non-woven cloth. Cloth prepreg materials are generally used for
hand laydown applications.
[0087] Fiber reinforced composite material (60) contains any of the
fibrous structural reinforcement fiber described herein that has
been impregnated with at least one high performance thermoplastic
polymer via any manufacturing/impregnation method known to those of
skill in the art. Suitable impregnation methods are known to those
of ordinary skill in the art and include, for example and without
limitation, hot-melt impregnation, aqueous slurry impregnation,
powder coating, extrusion film lamination, and combinations
thereof.
[0088] The high performance thermoplastic polymer for the surface
layer coating (50) and the high performance thermoplastic polymer
as the matrix resin for the fiber reinforced thermoplastic
composite material (60) can be the same or different materials or
combinations thereof.
[0089] The term "high performance polymer" is meant to refer to any
thermoplastic polymer that has a melting temperature (Tm) greater
than or equal to 280.degree. C. and a process temperature
(Tprocess) greater than or equal to 310.degree. C. In certain
embodiments, the higher performance polymer is chosen from
polyaryletherketones (PAEK), PAEK blends, polyimides, and
polyphenylenesulfides (PPS).
[0090] In certain embodiments, the PAEK is chosen from
polyetheretherketone (PEEK), polyetheretherketoneketone (PEEKK),
polyetherketoneketone (PEKK), polyetherketone (PEK), and
polyetherketoneketoneetherketone (PEKKEK). In still other
embodiments, the high performance polymer is a PAEK blend having
polyetherimide, polyphenylene sulfide and/or polyethersulfone mixed
in with one or more polyaryletherketones.
[0091] Polyaryletherketones are well known to those skilled in the
composite arts and include, but are not limited to, APC-2.RTM.
PEEK, CYPEK.RTM.-FC and/or CYPEK.RTM.-HT, all commercially
available from Cytec Industries Inc., Woodland Park, N.J.
[0092] Resin content of the high performance thermoplastic polymer
resin in the fiber reinforced composite material (60) ranges from
about 26% to about 90% by weight of the total thereby providing
composite material (60) with a resin modulus of 500 ksi or greater
and an interlaminar fracture toughness of 600 J/m.sup.2 or greater
as measure by G.sub.1c. The viscosity of the high performance
polymer is adjusted so that good filament wet out is obtained.
Ultimately, the high performance polymer of the fiber reinforced
composite material acts as part of a polymer matrix and forms a
polymer blend with the surface layer polymer coating (50) when the
materials are contacted. As used herein, the term "polymer blend"
includes miscible and compatible polymer blends as those terms are
known and understood by those skilled in the art to which the
invention pertains.
[0093] The resulting thermoplastic composite parts formed by the
present invention can be various articles formed using rapid
lamination and forming processes including, but not limited to, in
situ thermoplastic tape/tow placement for stiffened wing and
fuselage skins, continuous compression molding (CCM) and roll
forming process for stiffener fabrication, double belt press to
make consolidated flat panels and aircraft floor panels, in situ
filament wound cylindrical structures, and fusion bonding and
welding of composite assembly.
[0094] The following examples are provided to assist one skilled in
the art to further understand certain embodiments of the present
invention. These examples are intended for illustration purposes
and are not to be construed as limiting the scope of the various
embodiments of the present invention.
Example 1
Solvent Based PEI Polymer Sprayed Solution Applied to Tool
[0095] A formulation of PEI polymer, GE Ultem 1000P at 10% plus
Dioxilane at 90% was plasma sprayed onto the mold surface of a
steel mold tool which had a release film using an HVLP
applicator.
[0096] To test the transfer of the PEI/Dioxilane first ply lay-down
fiber reinforced thermoplastic composite, an 8 ply quasi-isotropic
panel was created using APC PEKK/AS-4 uni-tape material. The panel
was processed with a caul plate at an autoclave temperature of
720.degree. F. (382.degree. C.) and 100 psi of N.sub.2. The panel
showed some surface anomalies on the coated face.
Example 2
Water Based Slurry Hand Applied to Tool
[0097] A direct hand application technique was attempted using a
mixture that included surfactant, water, hydrosize (sizing) and
thermoplastic, as follows: 1) Sizing 90%/PEKK 10%. 2) D.I water
80%/Surfactant 10%/PEI-Diox. Premix solution 10%. 3) D.I water
80%/Surfactant 10%/PEKK 10%. 4) Sizing 80%/PEI powder
10%/Surfactant 10%). The resulting water based slurry thermoplastic
surface layer polymer coating shrank rapidly on the mold surface of
the mold tool and did not achieve adequate bonding onto metal mold
tool. The surface layer polymer coating flaked off very easily with
minimum abrasion.
Example 3
PEK Polymer Plasma Sprayed onto Mold Tool
[0098] To impart a coating directly onto the mold surface of a mold
tool applied with a sealer and release film, a plasma spray coating
was performed using a Praxair SG 100 plasma gun and introduced PEK
polymer into the jet stream to heat and accelerate the material to
high velocity. Initially there was difficulty maintaining adhesion
between the sealed/released tool and the PEK polymer, when the tool
was allowed to cool to room temperature, likely caused by the
difference in CTE (coefficient of thermal expansion) of the mold
tool and the thermoplastic surface layer polymer coating on the
smooth mold surface of the mold tool. It appeared that the skin
coating released from the tool (Hysol.RTM. Frekote.RTM. GP sealer
agent and release agent Frekote.RTM. 800).
Example 4
PEK Polymer Plasma Sprayed onto Textured Mold Surface of Mold
Tool
[0099] To improve adhesion of the plasma PEK polymer spray, a
subsequent panel was sandblasted using 120 grit aluminum oxide and
release coated with Frekote.RTM. 800. A much better coating
application was achieved.
[0100] To test how the PEK plasma-sprayed coatings transferred to a
laminate, two 8-ply quasi-isotropic panels were created using APC
PEKK/AS-4 uni-tape material. The panels were processed with a caul
plate at an autoclave temperature of 720.degree. F. (382.degree.
C.) and 100 psi of N.sub.2.
[0101] The resulting panels showed some uneven surface texture and
surface layer polymer coating thickness. Some areas of the surface
coating could be scraped off the resulting thermoplastic fiber
reinforced composite part. The mold surface of the mold tool was
clean after the autoclave cycle, indicating the mold release was
effective.
Example 5
Plasma PEK Polymer Sprayed Coating onto Prepreg
[0102] Plasma spraying was also conducted on APC-uni-tape samples
to provide a path to adding material to the outside of a
thermoplastic material. Two coated weights were deposited to test
the process control. Only one side of the tape was coated.
Transverse resin shrinkage and wrinkling of the tape was noted.
[0103] The unique capabilities of this process offer beneficial
uses such as combinations of materials including ceramic, metallic
and polymer blends that would be difficult to produce by other
means. Metal alloy coatings may provide improved electrical
conductivity for lightning strike and edge glow reduction.
Example 6
[0104] Thermoplastic composite parts are processed at high
temperatures and require stable tooling materials. The processing
cycle for PEKK-FC uni-tape panels exceeds 730.degree. F.
(388.degree. C.) which necessitates steel alloy tooling. For this
series of experiments the tooling was 0.120'' thick 304 stainless
steel plate.
[0105] Multiple surface finishes were tried during this experiment.
The default smooth panel was a 0.125'' thick stainless steel plate
that had been sanded with 120 grit sandpaper and solvent cleaned.
The textured surface treatments used included 120 grit aluminum
oxide and 40-60 c grit glass bead blasting. These surfaces
increased the mechanical locking of the first-ply coating to the
release-coated material. It is believed that the surface also broke
up the resin film by creating thick and thin areas that reduce the
effect of the resin shrinkage on tool adhesion. The glass-bead
blasted tool is recommended for plasma spraying but had not yet
been tried. The benefit of the texture is that it aids retention of
the coating during processing.
[0106] Zyvax Sealer GP was initially used to seal the stainless
plates. This was found to interact with the Frekote.RTM. 800 to
produce a surface with an exceptionally easy release. This causes
premature slip of the coating on the tool. After this was
discovered, the sealer was mechanically removed from all surfaces
and discontinued.
[0107] The first mold release evaluated was Hysol.RTM. Frekote.RTM.
800. This solvent-based system is known to offer release at
processing temperatures above 400.degree. C. The release was wiped
onto the stainless steel surface and allowed to air dry, and then
the tools were plasma sprayed with thermoplastic. Initial coating
used the PEI/dioxilane spray and showed a tendency to peel off the
tool with minimal abrasion. Kant-Stik Cure-Fast mold release was
then tried and was also found to have an easy-release surface. This
release has proven difficult to process above 750.degree. F.
(399.degree. C.).
[0108] AXEL 21RM mold release was then used without a sealer and
appeared to have a "tighter" surface than any of the previous
releases. It is a solvent-based system. The Axel 21RM is the
preferred available release for this application. It works without
a sealer to provide good surface adhesion without being too
slippery. A water-based version, W4005, was also tried to compare
to the AXEL 21RM, but found to be sensitive to abrasion with small
"marbles" of release evident after some finger abrasion of the
tool.
[0109] In keeping with the release manufacturer's recommendations,
the tools were heated to the use temperature (735.degree. F.,
391.degree. C.) to season the release onto the tool. Seasoning the
tool allows the release to be cured onto the tool before entering
service. This step was included to prevent solvent from the first
ply laydown using the PEI/dioxilane solution from lifting the mold
release film.
Example 7
[0110] To impart a coating directly onto a release-coated tool, a
plasma spray coating was performed using a plasma gun and
introduced PEK polymer into the jet stream to heat and accelerate
the material to high velocity. The PEK polymer is fed to the plasma
gun using a fluidized bed feeder system.
[0111] This time the tool was pre-heated to 250.degree. F.
(121.degree. C.) to aid in adhering the polymer to the surface of
the tool. A Praxair SG 100 plasma gun was used to deposit
approximately 2 mils of PEK polymer on to the tool. This
temporarily deposits the powder onto the tool. The stainless steel
tools with the powder coating were then processed in an electric
furnace at 750.degree. F. (399.degree. C.) to melt the polymer and
create a melted polymer layer.
[0112] To improve adhesion of the plasma spray, a subsequent panel
was sandblasted using 120 grit aluminum oxide and release coated
with Hysol.RTM. Frekote.RTM. 800. A picture frame of tape was
placed on the tool to create a rough center panel and a smooth
perimeter. This picture frame was intended to show the effect of
surface roughness transitions on the first ply lay-down materials.
This also provides a smooth area for masking off tool
overspray.
[0113] To test how the PEK plasma-sprayed coatings transferred to a
laminate, an 8-ply quasiisotropic panel was created using APC
PEKK/AS-4 uni-tape material. The panel was processed with a caul
plate at an autoclave temperature of 720.degree. F. (382.degree.
C.) and 100 psi of N.sub.2. The resulting panel showed somewhat
un-even texture and coating thickness. The coated tool surfaces
were clean after the autoclave cycle, indicating the mold release
was effective.
[0114] Film Lamination using bi- or tri-layer in situ thermoplastic
tape: A small press was heated to between 290.degree. C. and
410.degree. C. Kapton film is coated with a release agent and, with
the press at the desired temperature; a bi- or tri-layer
configuration is sandwiched between two pieces of the release agent
coated Kapton film, thereby forming a lay-up. The lay-up is placed
between the two 3''.times.3'' stainless steel caul plates of the
press along with a thermocouple. The stack is inserted into the
press and 1,000 pounds of pressure is applied and held for a period
of from 10 to 30 seconds. The pressure and top plate is then
released and the stack is removed to cool under a cold press (1000
lbs. for 1 minute).
[0115] In view of the above description and examples, one of
ordinary skill in the art will be able to practice the disclosure
as claimed without undue experimentation.
[0116] Although the foregoing description has shown, described, and
pointed out the fundamental novel features of the present
teachings, it will be understood that various omissions,
substitutions, and changes in the form of the detail of the
apparatus as illustrated, as well as the uses thereof, may be made
by those skilled in the art, without departing from the scope of
the present teachings. Consequently, the scope of the present
teachings should not be limited to the foregoing discussion, but
should be defined by the appended claims.
* * * * *