U.S. patent application number 11/726821 was filed with the patent office on 2008-09-25 for repair of a composite sandwich structure having a perforated skin.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to William F. Bogue, John M. Robertson.
Application Number | 20080233346 11/726821 |
Document ID | / |
Family ID | 39500037 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080233346 |
Kind Code |
A1 |
Bogue; William F. ; et
al. |
September 25, 2008 |
Repair of a composite sandwich structure having a perforated
skin
Abstract
A method of restoring a section of a composite having a
honeycomb bonded to a perforated skin includes the steps of
separating a first honeycomb from the perforated skin to expose a
portion of the perforated skin, inserting pins through perforations
in the perforated skin, extending the pins through a repair
material, attaching the repair material to the exposed portion of
the perforated skin, and attaching a second honeycomb to the repair
material. The method may include removing material from the exposed
portion of the perforated skin, prior to inserting pins through the
perforations, to create a more even bonding surface for attaching
the repair material.
Inventors: |
Bogue; William F.; (Hebron,
CT) ; Robertson; John M.; (Andover, CT) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
THE KINNEY & LANGE BUILDING, 312 SOUTH THIRD STREET
MINNEAPOLIS
MN
55415-1002
US
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
39500037 |
Appl. No.: |
11/726821 |
Filed: |
March 23, 2007 |
Current U.S.
Class: |
428/116 ;
156/94 |
Current CPC
Class: |
Y10T 428/236 20150115;
B29L 2031/608 20130101; B29C 73/10 20130101; B29C 73/06 20130101;
Y10T 428/24149 20150115; Y10T 156/1082 20150115; Y10T 156/1056
20150115; Y10T 428/24165 20150115 |
Class at
Publication: |
428/116 ;
156/94 |
International
Class: |
B32B 3/12 20060101
B32B003/12; B32B 43/00 20060101 B32B043/00 |
Claims
1. A method of restoring a section of a composite having a
honeycomb bonded to a perforated skin, the method comprising:
separating a first honeycomb from the perforated skin to expose a
portion of the perforated skin; inserting pins through perforations
in the perforated skin; extending the pins through a repair
material; attaching the repair material to the exposed portion of
the perforated skin; and attaching a second honeycomb to the repair
material.
2. The method of claim 1 further comprising: removing the pins from
the perforations in the perforated skin.
3. The method of claim 1 further comprising: positioning the pins
in a retaining device prior to inserting the pins through the
perforations in the perforated skin.
4. The method of claim 1 further comprising: removing material from
the exposed portion of the perforated skin to create an even
bonding surface prior to inserting the pins through the
perforations in the perforated skin.
5. The method of claim 1 further comprising: applying an adhesive
to an exposed portion of the perforated skin prior to inserting
pins through perforations in the perforated skin.
6. The method of claim 5 wherein the adhesive is a paste epoxy.
7. The method of claim 1 wherein the repair material includes at
least one leveling ply.
8. The method of claim 7 wherein the leveling ply is
fiberglass.
9. The method of claim 1 wherein attaching the repair material to
the exposed portion of the perforated skin includes bonding a first
adhesive layer to the perforated skin and bonding the repair
material to the first adhesive layer.
10. The method of claim 9 wherein attaching a second honeycomb to
the repair material includes bonding a second adhesive layer to the
repair material and bonding the second honeycomb to the second
adhesive layer.
11. The method of claim 10 wherein the repair material, the first
adhesive layer and the second adhesive layer each include an epoxy
resin.
12. The method of claim 1 wherein the composite includes a solid
skin and the honeycomb is sandwiched between the solid skin and the
perforated skin.
13. The method of claim 12 further comprising: removing a first
section of the solid skin from the composite prior to separating
the first honeycomb from the perforated skin.
14. The method of claim 13 further comprising: attaching a
replacement section of solid skin to the composite to cover the
second honeycomb.
15. The method of claim 14 further comprising: attaching at least
one ply to the solid skin to cover the replacement section of solid
skin.
16. A composite having a section restored by the method of claim
1.
17. The composite of claim 16 wherein the composite is a part in an
aircraft engine.
18. The composite of claim 16 wherein the composite is an acoustic
liner of a gas turbine engine.
19. A method of restoring a section of a composite having a
perforated skin, a solid skin and a honeycomb between the
perforated skin and the solid skin, the method comprising: (a)
removing an undesirable section of the honeycomb and a
corresponding section of the solid skin from the perforated skin,
wherein an exposed portion of the perforated skin includes an
uneven surface; (b) removing at least a portion of the uneven
surface to form a bonding surface on the exposed portion of the
perforated skin; (c) inserting pins into openings in the perforated
skin; (d) bonding a repair material to the exposed portion of the
perforated skin, wherein the pins are extended through the repair
material; (e) bonding a replacement honeycomb to the repair
material; (f) bonding a replacement solid skin to the replacement
honeycomb; and (g) removing the pins from the openings in the
perforated skin.
20. The method of claim 19 wherein removing a section of the solid
skin in step (a) includes tapering a remaining portion of the solid
skin around the undesirable section of the honeycomb.
21. The method of claim 19 wherein the uneven surface of the
perforated skin includes compressed sections and uncompressed
sections, and removing a portion of the uneven surface in step (b)
includes removing at least a portion of the uncompressed
sections.
22. The method of claim 19 further comprising: positioning the pins
in a retaining device prior to inserting the pins into the openings
in the perforated skin in step (c).
23. The method of claim 19 wherein the repair material is formed
from at least one ply of fiberglass.
24. The method of claim 19 wherein bonding a repair material on the
exposed portion of the perforated skin further comprises: attaching
a first adhesive layer to the exposed portion of the perforated
skin; bonding the repair material to the first adhesive layer; and
bonding a second adhesive layer to the repair material.
25. The method of claim 24 wherein the pins are extended through
the first adhesive layer and the second adhesive layer.
26. The method of claim 24 wherein the first adhesive layer is
attached to the exposed portion of the perforated skin prior to
inserting the pins into the openings in the perforated skin in step
(c).
27. The method of claim 19 further comprising: attaching an
adhesive around a perimeter of the replacement honeycomb prior to
step (e) to support the replacement honeycomb.
28. The method of claim 19 further comprising: attaching a cover
material to the solid skin after step (f) to cover the replacement
solid skin.
29. A composite having a restored section of honeycomb, the
composite comprising: a honeycomb having a first end and a second
end; a perforated skin bonded to a first end of the honeycomb; a
back skin bonded to a second end of the honeycomb; and a repair
section comprising: a plurality of removable pins located in
perforations in a portion of the perforated skin; at least one
repair ply attached to the portion of the perforated skin, wherein
the removable pins are removably extended through the at least one
repair ply; a replacement honeycomb having a first end attached to
the at least one repair ply; and a replacement back skin attached
to a second end of the replacement honeycomb.
30. The composite of claim 29 wherein the repair section further
comprises: an adhesive attached to a perimeter of the replacement
honeycomb to support the replacement honeycomb and attach the
replacement honeycomb to the honeycomb.
31. The composite of claim 29 wherein the repair section further
comprises: a second adhesive between the second end of the
replacement honeycomb and the replacement back skin.
32. The composite of claim 31 wherein the repair section further
comprises: a film adhesive having a first side attached to the
second adhesive and a second side attached to the replacement back
skin.
33. The composite of claim 29 further comprising: a cover ply
attached to the back skin to cover the replacement back skin.
34. The composite of claim 29 further comprising: an adhesive to
bond the at least one repair ply to the portion of the perforated
skin.
35. The composite of claim 34 wherein the adhesive includes at
least one of an epoxy film adhesive and a paste epoxy.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] Reference is made to the following pending applications:
U.S. patent application Ser. No. 11/441,866, entitled "REPAIR OF
COMPOSITE SANDWICH STRUCTURES WITH UNEVEN BOND SURFACES" and filed
on May 26, 2006; and U.S. patent application Ser. No. 11/441,893,
entitled "REPAIR OF PERFORATED ACOUSTIC SKINS BY REVERSE PIN
TRANSFER MOLDING" and filed on May 26, 2006.
BACKGROUND
[0002] The present invention relates to composite structures. More
particularly, the present invention relates to repairing composite
structures having a perforated skin and a honeycomb core.
[0003] Composite structures are commonly known and used in, for
example, gas turbine engines for aerodynamic fairings. One type of
composite is a sandwich structure having a face skin, a back skin,
and a honeycomb core inserted between and bonded to the face skin
and the back skin. The face skin and the back skin may be laminated
structures with a resin matrix, such as epoxy, and one or more
plies of fiberglass. The face skin commonly includes holes or
perforations that extend through a thickness of the face skin to
the honeycomb.
[0004] The honeycomb may become damaged over time from an impact,
elevated temperatures, abrasion, erosion, and/or other factors. In
some instances, the honeycomb may be damaged even though there is
no damage to the face skin. In some instances, it may be desirable
to locally replace a section of honeycomb from the back skin side,
rather than replace the entire composite structure. For example, a
section of the original honeycomb and a corresponding section of
the back skin may be cut out of the composite, and a replacement
honeycomb and a replacement back skin may be attached to the face
skin.
[0005] In a composite having a sandwich structure, ends of the
original honeycomb press into the back skin and the face skin to
form a dimpled imprint surface on the skins. The dimpled imprint
results in each skin having compressed and uncompressed sections,
which remain after the original honeycomb is removed. This uneven
surface on the face skin makes it difficult to bond a replacement
section of honeycomb to the face skin. Thus, it may be necessary to
remove some of the face skin to create a more even bonding surface,
before attaching the replacement honeycomb to the face skin.
[0006] Fiberglass leveling plies and adhesive may be attached to
the prepared bonding surface of the face skin, prior to bonding the
replacement section of honeycomb to the face skin. During a curing
cycle, the perforations of the face skin commonly become blocked
with adhesive, resin or fiberglass. Reforming the perforations is
time consuming and may structurally damage or weaken the restored
composite after curing is complete. There is a need for a method of
maintaining the perforations in the face skin during a local repair
of the honeycomb and the back skin of the composite.
BRIEF SUMMARY OF THE INVENTION
[0007] A method of restoring a section of a composite having a
honeycomb bonded to a perforated skin includes the steps of
separating a first honeycomb from the perforated skin to expose a
portion of the perforated skin, inserting pins through perforations
in the perforated skin, extending the pins through a repair
material, attaching the repair material to the exposed portion of
the perforated skin, and attaching a second honeycomb to the repair
material. In some embodiments, prior to inserting pins through the
perforations, material is removed from the exposed portion of the
perforated skin to reduce surface variation in the perforated skin
and create a more even bonding surface. In some embodiments, the
repair material may include at least one leveling ply and an
adhesive layer attached to either or both sides of the leveling ply
(or plies).
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross-section of a composite structure having a
honeycomb core sandwiched between a perforated face skin and a back
skin.
[0009] FIG. 2 is an expanded cross-sectional view of a portion of
the composite structure of FIG. 1.
[0010] FIG. 3 is a cross-section of the composite structure of FIG.
1 to illustrate an initial step in the repair process in which a
portion of the honeycomb core and the back skin are removed.
[0011] FIG. 4 is a perspective view of the composite structure of
FIG. 3.
[0012] FIG. 5 is a cross-section of a portion of the face skin of
the composite structure to illustrate a step in the repair process
to make a bonding surface of the face skin more even.
[0013] FIGS. 6-9 illustrate subsequent steps in the repair process
to complete replacement of a section of the honeycomb core and the
back skin.
[0014] It is recognized that the figures are not necessarily to
scale.
DETAILED DESCRIPTION
[0015] FIG. 1 is a schematic of composite structure 10 which
includes face skin 12 having perforations 14, back skin 16 and
honeycomb core 18. As an example, composite structure 10 may be an
acoustic liner used in a fan-bypass area or nacelle of a gas
turbine engine for noise attenuation.
[0016] As shown in the exemplary embodiment of FIG. 1, each of face
skin 12 and back skin 16 include three composite layers 20. Each
composite layer 20 may be made, for example, of a resin matrix with
continuous woven fiber reinforcement. The fibers may include, but
are not limited to, fiberglass. The resin may include, but is not
limited to, epoxy. Although in FIG. 1 skins 12 and 16 each include
three composite layers, it is recognized that more or less layers
may be used. Perforations 14 are openings in face skin 12 that
extend through a thickness of face skin 12 from an airflow side, A,
to honeycomb core 18. Honeycomb core 18 includes cell chambers 22,
which operate in conjunction with perforations 14 of face skin 12
in a known manner to attenuate noise. In the exemplary embodiment
of composite structure 10 shown in FIG. 1, back skin 16 is a solid
skin (i.e. it does not include perforations).
[0017] A portion of honeycomb core 18 may become damaged, and it
may be necessary or beneficial to locally replace a portion of
honeycomb core 18, and a corresponding section of back skin 16. A
repair process is described herein for replacing a portion of
honeycomb core 18 and back skin 16 in such a way that composite
structure 10 maintains its structural, acoustic, and dimensional
properties. Moreover, the repair process includes a method of
maintaining perforations 14 in face skin 12 that are located in a
region where honeycomb core 18 is replaced. This avoids a need of
having to reform perforations 14 in face skin 12 when the repair of
honeycomb core 18 is complete, which may be time or labor
intensive, and, more importantly, may damage composite structure 10
or reduce its structural integrity.
[0018] FIG. 2 is an expanded view of a portion of composite
structure 10 of FIG. 1 to further illustrate a configuration of
honeycomb core 18 having a first end 18a, a second end 18b and cell
chambers 22. As shown in FIG. 2, first end 18a of core 18 is bonded
to face skin 12 and second end 18b of core 18 is bonded to back
skin 16. At each end 18a and 18b of core 18 where cell chambers 22
of honeycomb core 18 contact face skin 12 and back skin 16,
composite layers 20 of skins 12 and 16 are compacted or compressed
by a force from cell chambers 22. In between cell chambers 22,
composite layers 20 are uncompressed. Thus, as shown in FIG. 2,
alternating compressed and uncompressed sections of composite
layers 20 result in a draped pattern across face skin 12 and back
skin 16. (Although not clearly visible in FIGS. 1 and 2, each cell
chamber 22 has a hexagonal shape, which forms a hexagonal imprint
on face skin 12 and back skin 16, as more clearly shown in FIG. 4.)
In the exemplary embodiment shown in FIG. 2, perforations 14 of
face skin 12 are shown centered within each cell chamber 22 of
honeycomb core 18. It is recognized that perforations 14 may be
offset from cell chambers 22. It is also recognized that more or
less perforations may be formed in face skin 12 relative to cell
chambers 22, but it is preferred that at least one perforation 14
extends into each hexagonal cell chamber 22 to enhance acoustic
attenuation, as more clearly depicted in FIG. 4.
[0019] FIG. 3 illustrates a first step in the repair process to
replace a portion of honeycomb core 18 of composite structure 10.
As shown in FIG. 3, a portion of honeycomb core 18 and back skin 16
have been removed from structure 10. Prior to removing a portion of
core 18, a larger portion of back skin 16 is first removed. In the
embodiment shown in FIG. 3, the portion of back skin 16 is removed
in such a way that, in area 24, remaining back skin 16 has tapered
structures on each side that gradually slope downward towards area
26, where honeycomb core 18 is to be removed. Back skin 16 and
honeycomb core 18 may be removed from areas 24 and 26 in any number
of different ways. For example, back skin 16 may first be removed
from areas 24 and 26 by cutting composite layers 20; then honeycomb
core 18 may be cut-out from area 26. Alternatively, back skin 16
may be removed first from only area 24, and then back skin 16 may
be removed from area 26 with the same cuts used to remove honeycomb
core 18 from area 26.
[0020] Instead of a sloped taper in area 24, as shown in FIG. 3,
back skin 16 may have a stepped taper. Although it is not required
that remaining back skin 16 is tapered in area 24, the tapered
structure supports a replacement back skin (see FIG. 9). The
overlap between original back skin 16 and the replacement skin
provides structural strength to composite structure 10 by allowing
loads to be transferred between original back skin 16 and the
replacement skin.
[0021] FIG. 4 is a perspective view of composite structure 10 of
FIG. 3 after a portion of honeycomb core 18 and back skin 16 have
been removed. As shown in FIG. 4, area 24 is the portion where back
skin 16 is tapered on both sides of area 26. Area 26 represents the
area where honeycomb core 18 and back skin 16 have been removed or
cut-out to expose face skin 12. As shown in FIG. 4, an exposed
portion 12a of face skin 12 in area 26 includes a dimpled imprint
left-over from the removed honeycomb core.
[0022] Although not visible in FIGS. 3 and 4, exposed portion 12a
of face skin 12 in area 26 is an uneven surface which is caused by
the compression of cell chambers 22 at first end 18a of honeycomb
core 18 in some areas of face skin 12 (see FIG. 2). Thus, the
repair process includes a partial leveling of exposed portion 12a
of face skin 12 to produce a more even bonding surface for
receiving a repair material and a replacement honeycomb.
[0023] FIG. 5 is a cross-sectional view of exposed portion 12a of
face skin 12 from area 26 of FIG. 4. The dimpled imprint on face
skin 12 includes compressed sections 30 where ends of cell chambers
22 pressed into face skin 12, and relatively uncompressed sections
32 that were between the ends of cell chambers 22. This structure
results in face skin 12 having uneven surface 34.
[0024] In the exemplary embodiment of composite structure 10, face
skin 12 includes three fiberglass layers 20a, 20b and 20c having a
cured epoxy resin matrix. High spots of top composite layer 20a may
be locally removed, as shown in FIG. 5, such that middle composite
layer 20b is exposed. This results in a more even surface 36 for
bonding a replacement honeycomb section thereto. (Surface 36 may
also be referred to as bonding surface 36.) A flatter bonding
surface facilitates a more durable bond between surface 36 and
whatever it is bonded to because the adhesive thickness is less
variable. As shown in FIG. 5, one composite layer 20a was removed
from face skin 12. It is recognized that more than one composite
layer or less than one composite layer may be removed. (For
reference, see U.S. patent application Ser. No. 11/441,866,
entitled "REPAIR OF COMPOSITE SANDWICH STRUCTURES WITH UNEVEN BOND
SURFACES.")
[0025] FIG. 5 shows face skin 12 as removal of top composite layer
20a is in progress. Top layer 20a may be removed in a variety of
different ways. For example, top layer 20a of face skin 12 is
mechanically removed using a grinding, sanding, or other known
mechanical process.
[0026] After completing removal of top layer 20a, such that exposed
portion 12a of face skin 12 is essentially an even surface, a
repair material may be attached to bonding surface 36. The repair
material is configured to adequately bond face skin 12 to a
replacement section of honeycomb. Because adhesive and a curing
process are involved in attaching the repair material to surface 36
of face skin 12, perforations 14 in face skin 12 may become blocked
with adhesive and/or repair material during the repair process. In
order to maintain perforations 14, pins may be inserted through
some of perforations 14 of face skin 12 prior to attaching the
repair material.
[0027] FIG. 6 is a schematic of composite structure 10 after pins
40 have been inserted through perforations 14 to maintain
perforations 14 during attachment of the repair material to a
portion of face skin 12. (Note that in FIG. 6, in area 26, face
skin 12 only includes two composite layers 20b and 20c, since
portions of top composite layer 20a were removed prior to insertion
of pins 40.) As shown in FIG. 6, pins 40 are not inserted through
all of perforations 14 of face skin 12; rather, pins 40 are
inserted through those perforations in area 26 where honeycomb core
18 has been removed. Moreover, an extra pin 40a is inserted on each
side of area 26 to account for any adhesive run-off during the
curing process. It is recognized that pins 40 may be inserted into
all perforations 14 of face skin 12; however, this may be time
consuming and is not necessary.
[0028] Pins 40 are inserted through face skin 12 with the aid of
retaining plate 42. A rubber caul may be substituted for retaining
plate 42. Generally speaking, any structure may be used if it is
capable of receiving pins 40, and being temporarily secured to face
skin 12, such that pins 40 are fixed inside perforations 14 and
face skin 12 is supported during the curing cycle.
[0029] A diameter of pins 40 is essentially equal to or slightly
less than a diameter of perforations 14. A length of pins 40 may
vary so long as pins 40 are long enough to extend through plate 42,
composite layers 20 and into an open space of area 26. Pins 40 are
preferably short enough to not extend into an area originally
occupied by back skin 16.
[0030] FIG. 7 is an expanded view of a portion of composite
structure 10 of FIG. 6 after repair layer 49 has been bonded to
surface 36 of face skin 12. Repair layer 49 includes repair
material 44 sandwiched between adhesive layers 46 and 48. Repair
layer 49, with original composite layers 20b and 20c, now
constitutes face skin 12. As shown in FIG. 7, adhesive 46 may first
be attached to surface 36 to strengthen the bond between surface 36
and repair layer 49. In an exemplary embodiment, adhesive 46 may be
an epoxy film adhesive. In some embodiments, repair material 44 is
similar to or identical to composite layers 20 used in face skin
12, except that material 44 is not yet compacted and resin in
material 44 is not yet cured. Repair material 44 may be formed from
one or more plies of fiberglass and may contain epoxy resin.
Another adhesive layer 48 may be applied to repair material 44 to
promote bonding between repair material 44 and a replacement
section of honeycomb (see FIG. 8). Adhesive layer 48, for example,
also may be an epoxy film adhesive. In some embodiments, the resin
in adhesive layers 46 and 48 and the resin in repair material 44
may all be the same resin or otherwise compatible epoxy resins.
[0031] Prior to a curing process, repair material 44 is
conformable. To attach repair material 44 to surface 36 of face
skin 12, pins 40 are pushed through repair material 44 or repair
material 44 is worked over pins 40. In either case, the result is
that pins 40 extend through repair material once repair material 44
is bonded to surface 36 of face skin 12. Pins 40 are similarly
pushed through adhesive layers 46 and 48, or adhesive layers 46 and
48 are worked over pins 40. In alternative embodiments, adhesive
layer 46 may be a paste epoxy that is disposed onto surface 36
prior to insertion of pins 40.
[0032] FIG. 8 is a cross-sectional view of composite structure 10
illustrating a subsequent step in the repair process in which
replacement honeycomb core 50 is inserted into area 26 and attached
to face skin 12, which includes repair layer 49 and original
composite layers 20b and 20c. More specifically, honeycomb core 50
bonds with adhesive layer 48 (see FIG. 7) of repair layer 49 to
attach to face skin 12. Honeycomb core 50 is similar to honeycomb
core 18 and includes cell chambers 53.
[0033] Because honeycomb core 50 is configured such that it may
collapse if it is not adequately supported, core splice adhesive 52
may be attached around a perimeter of honeycomb core 50 prior to
attaching honeycomb core 50 to face skin 12. Adhesive 52 is used to
support core 50, and to attach core 50 to original honeycomb core
18. Adhesive 52 may include any type of light-weight material, such
as, but not limited to, an epoxy foaming adhesive, an epoxy potting
compound, or an epoxy paste adhesive.
[0034] It is not necessary that cell chambers 53 of replacement
honeycomb core 50 match up exactly with a pattern of original
honeycomb core 18. However, if possible, positioning of replacement
honeycomb core 50 may be adjusted to minimize obstruction of
perforations 14 and to avoid pins 40 while replacement honeycomb
core 50 is being positioned in area 26.
[0035] FIG. 9 is a cross-sectional view of composite 10 of FIG. 8
illustrating a final step in the repair process in which
replacement back skin 54 is attached to replacement honeycomb core
50 (in area 26) and to original back skin 16 (in area 24). In the
exemplary embodiment of FIG. 9, replacement back skin 54 includes
three composite layers 55, which may be similar to or identical to
composite layers 20 of original back skin 16. Adhesive layer 56 may
be used to bond replacement back skin 54 to replacement honeycomb
50 and to composite layers 20 of original back skin 16. Adhesive
layer 56 may include any suitable adhesive, such as an epoxy film
adhesive. Replacement honeycomb core 50 may include adhesive layer
58 at a top portion of core 50 to further promote bonding between
core 50 and skin 54.
[0036] Finally, cover ply 68 may be used to reinforce replacement
back skin 54. As shown in FIG. 9, cover ply 68 preferably extends
beyond area 24; in an exemplary embodiment, cover ply 68 extends
beyond area 24 by at least. 0.75 inches. Adhesive layer 56 may be
approximately equal in dimensions to cover ply 68 such that
adhesive layer 56 extends beyond replacement back skin 54, and may
be used to attach cover ply 68 to original back skin 16. Cover ply
68 may be similar to composite layers 20 and 55.
[0037] High heat may next be applied to composite structure 10 to
cure any resins in the various adhesive layers or composite layers
in structure 10. The curing process results in structure 10
becoming a hardened laminate. Pins 40 may then be removed from
perforations 14, and plate 42 is detached from composite 10. With
the use of pins 40, perforations 14 in face skin 12 remain intact
and no additional steps are needed to reform perforations 14. The
restored area of composite 10, including replacement honeycomb core
50 and replacement back skin 54, is functionally equal to
surrounding areas of composite 10.
[0038] During the curing process, composite structure 10 may also
be placed under pressure, such that ends of replacement honeycomb
core 50 compress face skin 12, specifically repair material 44, and
replacement back skin 54. This results in the restored sections of
the face skin and the back skin having a draped pattern similar to
the pattern shown in FIG. 2.
[0039] The terminology used herein is for the purpose of
description, not limitation. Specific structural and functional
details disclosed herein are not to be interpreted as limiting, but
merely as bases for teaching one skilled in the art to variously
employ the present invention. Although the present invention has
been described with reference to preferred embodiments, workers
skilled in the art will recognize that changes may be made in form
and detail without departing from the spirit and scope of the
invention.
* * * * *