U.S. patent application number 11/645975 was filed with the patent office on 2008-07-03 for methods for fabricating composite structures with flanges having tethered corners.
Invention is credited to Lee Alan Blanton, Curt Brian Curtis, Frank Worthoff.
Application Number | 20080157418 11/645975 |
Document ID | / |
Family ID | 39296010 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080157418 |
Kind Code |
A1 |
Blanton; Lee Alan ; et
al. |
July 3, 2008 |
Methods for fabricating composite structures with flanges having
tethered corners
Abstract
Methods for fabricating a composite structure with a flange
having a tethered corner involving providing a composite structure
forming tool including a first endplate and a second endplate and
having a composite structure formed thereabout, applying at least
one ply of barrier fibers about the composite structure adjacent to
the first endplate of the composite structure forming tool, and
wrapping at least one fiber tow about the barrier fibers.
Inventors: |
Blanton; Lee Alan;
(Cincinnati, OH) ; Curtis; Curt Brian; (West
Chester, OH) ; Worthoff; Frank; (West Chester,
OH) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY
GE AVIATION, ONE NEUMANN WAY MD H17
CINCINNATI
OH
45215
US
|
Family ID: |
39296010 |
Appl. No.: |
11/645975 |
Filed: |
December 27, 2006 |
Current U.S.
Class: |
264/103 |
Current CPC
Class: |
B29C 70/32 20130101;
B29C 70/543 20130101; B29C 53/587 20130101; B29K 2105/0809
20130101; B29K 2105/101 20130101; B29C 70/20 20130101; B29L
2031/7504 20130101; B29L 2023/22 20130101 |
Class at
Publication: |
264/103 |
International
Class: |
B22F 7/06 20060101
B22F007/06 |
Claims
1. A method for fabricating a composite structure with a flange
having a tethered corner comprising: providing a composite
structure forming tool including a first endplate and a second
endplate and having a composite structure formed thereabout;
applying at least one ply of barrier fibers about the composite
structure adjacent to the first endplate of the composite structure
forming tool; and wrapping at least one fiber tow about the barrier
fibers.
2. The method of claim 1 wherein the barrier fibers are comprised
of a material selected from the group consisting of glass fibers,
graphite fibers, carbon fibers, ceramic fibers, aromatic polyamide
fibers, and combinations thereof.
3. The method of claim 1 wherein the fiber tow is comprised of a
material selected from the group consisting of glass fibers,
graphite fibers, carbon fibers, ceramic fibers, aromatic polyamide
fibers, and combinations thereof.
4. The method of claim 1 wherein the composite structure has a
circumference and the barrier fibers are wrapped about the
circumference of the composite structure adjacent to the first
endplate of the composite structure forming tool to form a flange
corner.
5. The method of claim 4 wherein the fiber tow is wrapped about the
barrier fibers in the flange corner.
6. The method of claim 1 wherein the composite structure is a gas
turbine engine fan casing.
7. The method of claim 1 wherein the flange is selected from the
group consisting of end flanges, mounting flanges and combinations
thereof.
8. The method of claim 1 wherein the barrier fibers comprise glass
fibers.
9. The method of claim 1 wherein the fiber tow comprises carbon
fiber.
10. The method of claim 1 wherein the fiber tow is wrapped about
the barrier fibers from 3 to 6 times.
11. The method of claim 1 wherein more than one fiber tow is
wrapped about the barrier fibers.
12. A method for fabricating a composite structure with a flange
having a tethered corner comprising: providing a composite
structure forming tool including a first endplate and a second
endplate and having a composite structure formed thereabout;
applying at least one ply of barrier fibers about the composite
structure adjacent to the first endplate of the composite structure
forming tool; wrapping at least one fiber tow about the barrier
fibers; applying at least one ply of filler fibers over the fiber
tow; and applying at least one ply of flange fibers over the filler
fibers to obtain a flange preform.
13. The method of claim 12 wherein the barrier fibers are comprised
of a material selected from the group consisting of glass fibers,
graphite fibers, carbon fibers, ceramic fibers, aromatic polyamide
fibers, and combinations thereof.
14. The method of claim 12 wherein the fiber tow is comprised of a
material selected from the group consisting of glass fibers,
graphite fibers, carbon fibers, ceramic fibers, aromatic polyamide
fibers, and combinations thereof.
15. The method of claim 12 wherein the composite structure has a
circumference and the barrier fibers are wrapped about the
circumference of the composite structure adjacent to the first
endplate of the composite structure forming tool to form a flange
corner.
16. The method of claim 15 wherein the fiber tow is wrapped about
the barrier fibers in the flange corner.
17. The method of claim 12 wherein the composite structure is a gas
turbine engine fan casing.
18. The method of claim 12 wherein more than one fiber tow is
wrapped about the barrier fibers.
19. The method of claim 12 further comprising curing the flange
preform to obtain a flange having a tethered corner.
20. The method of claim 12 wherein the flange is selected from the
group consisting of end flanges, mounting flanges and combinations
thereof.
Description
TECHNICAL FIELD
[0001] Embodiments described herein generally relate to methods for
fabricating composite structures with flanges having tethered
corners.
BACKGROUND OF THE INVENTION
[0002] In recent years composite materials have become increasingly
popular for use in a variety of aerospace applications because of
their durability and relative lightweight. Although composite
materials can provide superior strength and weight properties,
designing flanges on structures fabricated from composite materials
still remains a challenge.
[0003] Current flange lay-up processes can generally involve
repeatedly applying plies, or layers, of fabric to a composite
structure until a flange having the desired dimensions is obtained.
One issue that can arise during this process is that when a second
ply of fabric is applied, it can cover the first ply of fabric,
thereby making it nearly impossible to monitor the first ply to
ensure its placement is unchanged. As a result, bridging of the
fabric may occur.
[0004] Bridging is when the initial, or first, fabric ply pulls
away from the flange corner and spans across the corner rather than
remaining tightly adhered thereto. Bridging may result in resin
richness, which is an undesired agglomeration of excess resin
beneath the first ply of fabric that can locally weaken the
laminate.
[0005] Bridging may be caused by any of several factors. For
example, bridging may result from inadequately placing the initial
fabric plies into the corner of the flange such that as subsequent
plies are applied during lay-up the initial plies may be jostled
causing bridging. Also, inadequately removing bulk from the fabric
plies during layup can result in an excess length of composite
material, which can lead to bridging during the curing process.
Additionally, bridging may result from differences in thermal
expansion of the tooling versus the fabric during the curing
process.
[0006] Regardless of the cause, there is currently no way for
operators to easily monitor the initial fabric ply once it has been
covered to help ensure that bridging is prevented and that the
first ply of fabric remains adhered in the flange corner. The best
current practice is to terminate the fabric plies at the corner to
allow fabric slippage. However, this practice is generally only
beneficial in addressing the issue of differences in thermal
expansion during cure and does nothing to prevent bridging that
occurs as a result of jostling or inadequate bulk removal.
[0007] Accordingly, it would be desirable to provide methods for
fabricating flanges that are less susceptible to bridging and the
previously described fabrication concerns.
BRIEF DESCRIPTION OF THE INVENTION
[0008] Embodiments herein generally relate to methods for
fabricating composite structures with flanges having tethered
corners comprising providing a composite structure forming tool
including a first endplate and a second endplate and having a
composite structure formed thereabout, applying at least one ply of
barrier fibers about the composite structure adjacent to the first
endplate of the composite structure forming tool, and wrapping at
least one fiber tow about the barrier fibers.
[0009] Embodiments herein also generally relate to methods for
fabricating composite structures with flanges having tethered
corners comprising providing a composite structure forming tool
including a first endplate and a second endplate and having a
composite structure formed thereabout, applying at least one ply of
barrier fibers about the composite structure adjacent to the first
endplate of the composite structure forming tool, wrapping at least
one fiber tow about the barrier fibers, applying at least one ply
of filler fibers over the fiber tow and applying at least one ply
of flange fibers over the filler fibers to obtain a flange
preform.
[0010] These and other features, aspects and advantages will become
evident to those skilled in the art from the following
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] While the specification concludes with claims particularly
pointing out and distinctly claiming the invention, it is believed
that the embodiments set forth herein will be better understood
from the following description in conjunction with the accompanying
figures, in which like reference numerals identify like
elements.
[0012] FIG. 1 is a schematic perspective view of one embodiment of
a fan casing having end flanges and a mounting flange;
[0013] FIG. 2 is a schematic end view of FIG. 1;
[0014] FIG. 3 is a schematic perspective view of one embodiment of
a composite structure forming tool;
[0015] FIG. 4 is a schematic cross-sectional view of FIG. 2 along
line A-A; and
[0016] FIG. 5 is a schematic cross-sectional view of one embodiment
of a fan casing with a guide for fabricating a mounting flange
having tethered corners.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Embodiments described herein generally relate to methods for
fabricating composite structures with flanges having tethered
corners that can help eliminate the occurrence of bridging during
flange layup and cure. While embodiments herein may generally focus
on composite flanges on fan casings of gas turbine engines, it will
be understood by those skilled in the art that the description
should not be limited to such. Indeed, as the following description
explains, the tethered flange corners described herein may be
utilized on any flange fabricated from composite materials.
[0018] Turning to the figures, FIG. 1 illustrates one embodiment of
an acceptable composite structure 10. As used herein, "composite
structure" refers to any component fabricated from a composite
material or combination of composite materials. Composite structure
10 may comprise a generally cylindrical member, such as fan casing
12. Fan casing 12 may have a circumference, as shown in FIG. 2, and
as previously mentioned may be fabricated from any acceptable
material. In one embodiment, however, fan casing 12 may be
fabricated from a material selected from the group consisting of
glass fibers, graphite fibers, carbon fibers, ceramic fibers,
aromatic polyamide fibers such as poly(p-phenylenetherephtalamide)
fibers (i.e. KEVLAR.RTM.), and combinations thereof. In one
embodiment, fan casing 12 may be fabricated from carbon fibers.
[0019] As shown in FIG. 1, fan casing 12 may generally comprise a
cylindrical body 14 having a forward end 16 and an aft end 18. As
used herein, "fan casing" is used to refer to both pre- and
post-cure composite fan casings. Those skilled in the art will
understand which stage is being referenced from the present
description. Fan casing 12 may also comprise any number of end
flanges 20, as shown generally in FIGS. 1 and 2, and/or mounting
flanges 22, as shown generally in FIG. 1. As used herein, "mounting
flange" refers to any flange interposed circumferentially about
body 14 of fan casing 12, or other composite structure. By
"interposed" it is meant that mounting flange 22 may be located
circumferentially about body 14 of fan casing 12, as opposed to
about either of forward end 16 or aft end 18. In contrast, end
flange 20 may be located about either or both of forward end 16 or
aft end 18.
[0020] Fan casing 12 may be fabricated using any acceptable
fabrication method or tooling known to those skilled in the art.
See, for example, U.S. Patent Application Nos. 2006/0201135 to Xie
et al., and 2006/0134251 to Blanton et al. In one embodiment, as
shown in FIG. 3, a composite structure forming tool 24 may be used,
which has a circumference, a generally cylindrically shaped core
26, as well as a first endplate 28 and a second endplate 30 that
may be removeably coupled to core 26 of tool 24.
[0021] In FIG. 4 an illustrative embodiment of an end flange
preform 32 is shown on fan casing 12. It will be understood by
those skilled in the art that the following flange and lay-up
descriptions may be equally applicable to mounting flanges. End
flange preform 32 may include a tethered flange corner 33 which can
help anchor flange preform 32 in place during layup and cure.
Tethered flange corner 33 may comprise at least one ply of barrier
fibers 34 and at least one fiber tow 36 wrapped circumferentially
thereabout, as described herein below.
[0022] More specifically, tethered flange corner 33 may generally
include at least one ply of barrier fibers 34 applied adjacent to
first endplate 28 of tool 24 and fan casing 12, for example.
Barrier fibers 34 may be comprised of multidirectional textile
performs such as weaves or braids. As used herein,
"multidirectional" refers to textile preforms comprising fiber tows
oriented in more than one direction. Fiber tows of barrier fibers
34 may be comprised of any suitable reinforcing fiber known to
those skilled in the art, including, but not limited to, glass
fibers, graphite fibers, carbon fibers, ceramic fibers, aromatic
polyamide fibers, and combinations thereof. In one embodiment,
barrier fibers 34 may be comprised of glass fibers. Additionally,
each fiber tow of barrier fibers 34 may comprise from about 3000 to
about 24,000 fiber filaments.
[0023] Barrier fibers 34 may be applied in flange corner 37
adjacent to first endplate 28 of tool 24 and fan casing 12 by
wrapping barrier fibers 34 circumferentially about tool 24 and fan
casing 12 until the desired thickness is obtained. If so desired,
barrier fibers 34 may be tackified initially and upon completion of
application to fan casing 12 to hold barrier fibers 34 in place.
Any acceptable resin known to those skilled in the art may be used
to tackify barrier fibers 34, such as epoxy, for example.
[0024] Next, at least one individual fiber tow 36 may be wrapped
circumferentially about fan casing 12 over barrier fibers 34 in
flange corner 37. In this way, fiber tow 36 can complete tethered
flange corner 33 and help secure barrier fibers 34 in the desired
location. While fiber tow 36 may be wrapped about the circumference
of fan casing 12 any number of times, in one embodiment, fiber tow
36 may be wrapped from about 3 to about 6 times about the
circumference of fan casing 12. Alternately, more than one fiber
tow 36 may be wrapped about fan casing 12 one or more times to
achieve the same result. Fiber tow 36 may be fabricated from any
acceptable material known to those skilled in the art including,
but not limited to glass fibers, graphite fibers, carbon fibers,
ceramic fibers, aromatic polyamide fibers, and combinations thereof
However, in one embodiment, fiber tow 36 may be fabricated from
carbon fibers. Additionally, each fiber tow 36 utilized may
comprise from about 3000 to about 24,000 fiber filaments, and in
one embodiment about 12,000 fiber filaments. Once fiber tow 36 is
securely wrapped about barrier fibers 34 of tethered flange corner
33 it may be tackified using any acceptable resin known to those
skilled in the art, for example, epoxy, to hold it in place during
the fabrication of the remainder of end flange preform 32.
[0025] At least one ply of filler fibers 38 may then be applied
over fiber tow 36 to help fill in any space that may be present
between tethered flange corner 33 and the flange fibers that will
be subsequently applied. Similar to barrier fibers 34, a ply of
filler fibers 38 may be a multidirectional textile preform
comprised of any suitable reinforcing fiber known to those skilled
in the art, including, but not limited to, glass fibers, graphite
fibers, carbon fibers, ceramic fibers, aromatic polyamide fibers,
and combinations thereof. Also similar to barrier fibers 34, filler
fibers may be wrapped about the circumference of fan casing 12,
adjacent to first endplate 28 and over barrier fibers 34 and fiber
tow 36 until the desired thickness is obtained. If necessary,
filler fibers 38 may be tackified using any acceptable resin known
to those skilled in the art to help hold filler fibers 38 in place
throughout the rest of the fabrication process.
[0026] Flange fibers 40 may then be applied over filler fibers 38
using any known flange fabrication method known in the art to
complete fabrication of end flange preform 32. Once again, flange
fibers may comprise any suitable material such as glass fibers,
graphite fibers, carbon fibers, ceramic fibers, aromatic polyamide
fibers, and combinations thereof that can be wound about tool 24
over filler fibers 38.
[0027] To consolidate end flange preform 32, a debulking step may
be performed. In particular, reinforcing fibers, such as barrier
fibers 34, filler fibers 38 and flange fibers 40 may inherently
have a substantial amount of bulk. In order to help prevent
wrinkles and/or voids during the final cure of the material, and to
utilize near net shape tooling during the final cure, the fibers of
the material can be consolidated, or compressed, into a dimension
that is closer to the desired final cured thickness. This
consolidation occurs during debulk.
[0028] Debulk can be carried out using any common method known to
those skilled in the art, such as, for example, by applying
pressure to the composite fibers with either a vacuum bag, shrink
tape, or other mechanical means. Resin applied to the fibers before
debulk can help tack, or lock, the fibers in place once the
pressure is applied. If the tackified fibers cannot be consolidated
as desired at room temperature, then heat may be applied to lower
the viscosity of the resin. The resin may then better infiltrate
the composite fibers and allowing the consolidation to be carried
out to the desired degree.
[0029] Having finished laying up and debulking end flange preform
32, final cure tooling can be placed about fan casing 12, including
any end flange performs and mounting flange performs, to serve as a
mold during the curing process. As will be understood by those
skilled in the art, the final cure tooling and process may vary
according to such factors as resin used, part geometry, and
equipment capability.
[0030] As previously described, the foregoing is equally applicable
to mounting flanges as well as end flanges. When fabricating a
mounting flange preform 41, which is located about the body of fan
casing 12, a guide 42 may be used in place of first or second
endplate to provide a surface against which to apply barrier fibers
34 and fiber tow 36, as shown generally in FIG. 5. In one
embodiment, guide 42 may be comprised of discrete arcuate members,
each spanning about 180 degrees so as to fit correspondingly about
fan casing 12. The arcs of guide 42 may be releaseably connected
together for easy placement and adjustment about fan casing 12. It
will be understood, however, that guide 42 may be comprised of any
number of pieces and have any shape that corresponds to the shape
of the composite structure. As previously discussed, guide 42 can
serve as a support for the application of both barrier fibers 34
and fiber tow 36, as well as the remaining fiber layers of the
flange preform 41. Guide 42 may be circumferential and have an
L-shaped cross-section as shown, and may be constructed from any
rigid, lightweight material such as, for example, aluminum or
composite. Once one side of mounting flange preform 41 is
constructed, as shown in FIG. 5, guide 42 may be removed. The other
side of mounting flange preform 41 may then be constructed in the
same manner as the first side.
[0031] Embodiments of the tethered corner described herein can
provide several benefits. For example, applying the fiber tow about
the barrier fibers allows the fiber tow to serve as a tether to
hold the barrier fibers in the corner of the flange during
subsequent lay-up steps. More specifically, as additional plies of
filler fibers and/or flange fibers are placed and jostled, the
barrier fibers stay tethered in the corner because of the wrapped
fiber tow. This can help reduce or even eliminate the bridging
issue often faced in current flange fabrication processes.
[0032] Additionally, during curing, the composite structure forming
tool endplate and core have a tendency to expand and pull away from
one another due to the heat and pressure of the curing process.
This in turn can cause the barrier fibers to be pulled out of the
corner and result in bridging. The tethered corner created by the
fiber tow can help address this issue in two ways. First, the
tethered corner can reduce the occurrence of bridging in the first
instance by helping to hold the barrier fibers taught. Second,
during the curing process, the previously described expansion of
the composite structure forming tool can tighten the fiber tow of
the tethered corner, thereby effectively pulling it and the barrier
fibers against one another in the desired orientation and
reinforcing the adhesion therebetween.
[0033] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to make and use the invention. The patentable
scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal language
of the claims.
* * * * *