U.S. patent application number 12/625002 was filed with the patent office on 2010-05-27 for surfacing film for composite structures.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Dmitriy SALNIKOV.
Application Number | 20100129663 12/625002 |
Document ID | / |
Family ID | 41571667 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100129663 |
Kind Code |
A1 |
SALNIKOV; Dmitriy |
May 27, 2010 |
SURFACING FILM FOR COMPOSITE STRUCTURES
Abstract
A layered construction is provided having a storage modulus
G'.sub.t25 at 25.degree. C., comprising: a) a cured polymeric
composite having a storage modulus G'.sub.s25 at 25.degree. C.; and
b) a cured surfacing film bound thereto; wherein G'.sub.t25 is not
greatly elevated over G'.sub.s25, typically not more than 118% of
G'.sub.s25. In some embodiments the cured surfacing film comprises
an electrically conductive layer, typically a metal layer. In some
embodiments the cured surfacing film comprises a cured epoxy resin
which may optionally be a chain-extended epoxy resin and may
excludes phosphorus. The resulting layered construction may display
high erosion resistance, high corrosion resistance, and high
resistance to microcracking. In another aspect, methods of making
the subject layered constructions are provided.
Inventors: |
SALNIKOV; Dmitriy;
(Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
41571667 |
Appl. No.: |
12/625002 |
Filed: |
November 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61118242 |
Nov 26, 2008 |
|
|
|
Current U.S.
Class: |
428/413 ; 156/60;
428/457 |
Current CPC
Class: |
B64D 45/02 20130101;
B32B 15/08 20130101; B32B 27/38 20130101; B32B 2264/067 20130101;
Y10T 428/31678 20150401; B32B 27/42 20130101; Y10T 156/10 20150115;
Y10T 428/31511 20150401; B32B 27/285 20130101; B32B 2264/108
20130101; B32B 2270/00 20130101; B32B 27/18 20130101; B32B 27/34
20130101; B32B 7/02 20130101; B32B 2262/106 20130101; B32B 27/32
20130101; B32B 2262/101 20130101; B32B 2307/714 20130101; B32B
15/20 20130101; B32B 27/281 20130101; B32B 2264/02 20130101; B32B
2307/202 20130101; B32B 2264/12 20130101; B32B 2264/105 20130101;
B32B 27/36 20130101 |
Class at
Publication: |
428/413 ;
428/457; 156/60 |
International
Class: |
B32B 27/38 20060101
B32B027/38; B32B 15/08 20060101 B32B015/08; B32B 37/00 20060101
B32B037/00; H01B 1/02 20060101 H01B001/02 |
Claims
1. A layered construction having a storage modulus G'.sub.t25 at
25.degree. C., comprising: a) a cured polymeric composite having a
storage modulus G'.sub.s25 at 25.degree. C.; and b) a cured
surfacing film bound thereto; wherein G'.sub.t25 is no more than
118% of G'.sub.s25.
2. The layered construction according to claim 1 wherein G'.sub.t25
is no more than 110% of G'.sub.s25.
3. The layered construction according to claim 1 wherein G'.sub.t25
is no more than 104% of G'.sub.s25.
4. The layered construction according to claim 1 wherein G'.sub.t25
is between 101% and 118% of G'.sub.s25.
5. The layered construction according to claim 1 having a storage
modulus G'.sub.t-54 at -54.degree. C., wherein the cured polymeric
composite has a storage modulus G'.sub.s-54 at -54.degree. C.; and
wherein G'.sub.t-54 is no more than 122% of G'.sub.s-54.
6. The layered construction according to claim 5 wherein
G'.sub.t-54 is between 101% and 122% of G'.sub.s-54.
7. The layered construction according to claim 1 wherein the cured
surfacing film comprises an electrically conductive layer.
8. The layered construction according to claim 1 wherein the cured
surfacing film comprises an electrically conductive metal
layer.
9. The layered construction according to claim 1 wherein the cured
surfacing film comprises a cured chain-extended epoxy resin.
10. The layered construction according to claim 1 wherein the cured
surfacing film comprises no phosphorus.
11. The layered construction according to claim 1 wherein the cured
polymeric composite comprises a matrix polymer which is a different
composition from the cured surfacing film.
12. A method of making a layered construction comprising the steps
of: a) providing a curable polymeric composite which cures to form
a cured polymeric composite having a storage modulus G'.sub.s25 at
25.degree. C.; b) selecting a curable surfacing film; c) providing
said curable surfacing film; d) providing a tool having a shape
which is the inverse of the desired shape of the layered
construction; e) laying up the curable surfacing film and the
curable polymeric composite, in that order, in the tool; and f)
curing the curable polymeric composite and curable surfacing film
to make a layered construction, the layered construction having a
storage modulus G'.sub.t25 at 25.degree. C.; wherein step b) of
selecting a curable surfacing film comprises selecting a film such
that G'.sub.t25 is not more than 118% of G'.sub.s25.
13. The method according to claim 12 wherein step b) of selecting a
curable surfacing film comprises selecting a film such that
G'.sub.t25 is no more than 110% of G'.sub.s25.
14. The method according to claim 12 wherein step b) of selecting a
curable surfacing film comprises selecting a film such that
G'.sub.t25 is no more than 104% of G'.sub.s25.
15. The method according to claim 12 wherein step b) of selecting a
curable surfacing film comprises selecting a film such that
G'.sub.t25 is between 101% and 118% of G'.sub.s25.
16. The method according to claim 12 wherein the curable surfacing
film comprises an electrically conductive layer.
17. The method according to claim 12 wherein the curable surfacing
film comprises an electrically conductive metal layer.
18. The method according to claim 12 wherein the curable surfacing
film comprises a cured chain-extended epoxy resin.
19. The method according to claim 12 wherein the curable surfacing
film comprises no phosphorus.
20. The method according to claim 12 wherein the curable polymeric
composite comprises a matrix polymer which is a different
composition from the curable surfacing film.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
patent Application No. 61/118,242, filed on Nov. 26, 2008, the
disclosure of which is incorporated by reference herein in its
entirety.
FIELD OF THE DISCLOSURE
[0002] This invention relates to surfacing films for polymeric
fiber-reinforced composites, optionally including electrically
conductive layers, which display high erosion resistance, high
corrosion resistance, and high resistance to microcracking, the
films being selected such that the storage modulus of the composite
bearing the surfacing film is not greatly elevated compared to the
storage modulus of the bare composite.
SUMMARY OF THE INVENTION
[0003] Briefly, the present disclosure provides a layered
construction having a storage modulus G'.sub.t25 at 25.degree. C.,
comprising: a) a cured polymeric composite having a storage modulus
G'.sub.s25 at 25.degree. C.; and b) a cured surfacing film bound
thereto; wherein G'.sub.t25 is no more than 118% of G'.sub.s25,
more typically no more than 115%, more typically no more than 112%,
in some embodiments no more than 110%, in some embodiments no more
than 108%, in some embodiments no more than 106%, and in some
embodiments no more than 104%. In some of the foregoing
embodiments, G'.sub.t25 is at least 101% of G'.sub.s25. In other
embodiments, the present disclosure provides a layered construction
having a storage modulus G'.sub.t-54 at -54.degree. C., comprising:
a) a cured polymeric composite having a storage modulus G'.sub.s-54
at -54.degree. C.; and b) a cured surfacing film bound thereto;
wherein G'.sub.t-54 is no more than 122% of G'.sub.s-54, more
typically no more than 118%, more typically no more than 115%, more
typically no more than 111%, in some embodiments no more than 110%,
in some embodiments no more than 107%, and in some embodiments no
more than 104%. In some of the foregoing embodiments, G'.sub.t-54
is at least 101% of G'.sub.s-54. In some embodiments the cured
surfacing film comprises an electrically conductive layer,
typically a metal layer, which may optionally be a foil, expanded
foil, mesh, cloth, wires, or the like. In some embodiments the
cured surfacing film comprises a cured epoxy resin which may
optionally be a chain-extended epoxy resin. Typically the resin
excludes phosphorus. In some embodiments the layered construction
displays high erosion resistance. In some embodiments the layered
construction displays high corrosion resistance. In some
embodiments the layered construction displays high resistance to
microcracking. In some embodiments the layered construction
displays high resistance to microcracking in response to thermal
shock. In some embodiments the layered construction displays high
resistance to microcracking in response to mechanical stress.
[0004] In another aspect, the present disclosure provides a method
of making a layered construction comprising the steps of: a)
providing a curable polymeric composite; b) providing a curable
surfacing film; c) providing a tool having a shape which is the
inverse of the desired shape of the layered construction; d) laying
up the curable surfacing film and the curable polymeric composite,
in that order, in the tool; and e) curing the curable polymeric
composite and curable surfacing film. In some embodiments, the
resulting layered construction has a storage modulus G'.sub.t25 at
25.degree. C., wherein a construction made in the same manner but
lacking the curable surfacing film has a storage modulus G'.sub.s25
at 25.degree. C.; and wherein G'.sub.t25 is no more than 118% of
G'.sub.s25, more typically no more than 115%, more typically no
more than 112%, in some embodiments no more than 110%, in some
embodiments no more than 108%, in some embodiments no more than
106%, and in some embodiments no more than 104%. In some of the
foregoing embodiments, G'.sub.t25 is at least 101% of G'.sub.s25.
In other embodiments, the resulting layered construction has
storage modulus G'.sub.t-54 at -54.degree. C., wherein a
construction made in the same manner but lacking the curable
surfacing film has a storage modulus G'.sub.s-54 at -54.degree. C.;
wherein G'.sub.t-54 is no more than 122% of G'.sub.s-54, more
typically no more than 118%, more typically no more than 115%, more
typically no more than 111%, in some embodiments no more than 110%,
in some embodiments no more than 107%, and in some embodiments no
more than 104%. In some of the foregoing embodiments, G'.sub.t-54
is at least 101% of G'.sub.s-54. In some embodiments, curing is
carried out under sub-atmospheric pressure, typically less than 90%
of one atmosphere, more typically less than 50% of one atmosphere,
and more typically less than 10% of one atmosphere. In some
embodiments the curable surfacing film comprises an electrically
conductive layer, typically a metal layer, which may optionally be
a foil, expanded foil, mesh, cloth, wires, or the like. In some
embodiments the curable surfacing film comprises a curable epoxy
resin which may optionally be a chain-extended epoxy resin.
Typically the resin excludes phosphorus. In some embodiments the
resulting layered construction displays high erosion resistance. In
some embodiments the resulting layered construction displays high
corrosion resistance. In some embodiments the resulting layered
construction displays high resistance to microcracking. In some
embodiments the resulting layered construction displays high
resistance to microcracking in response to thermal shock. In some
embodiments the resulting layered construction displays high
resistance to microcracking in response to mechanical stress.
BRIEF DESCRIPTION OF THE DRAWING
[0005] FIG. 1 is diagram of a layered construction as described in
the Examples section, below.
[0006] FIG. 2 is diagram of a layered construction as described in
the Examples section, below.
[0007] FIG. 3 is a micrograph of a prior art layered construction
as described in the Examples section, below.
[0008] FIG. 4 is a micrograph of a prior art layered construction
as described in the Examples section, below.
[0009] FIG. 5 is a micrograph of a prior art layered construction
as described in the Examples section, below.
[0010] FIG. 6 is a micrograph of a prior art layered construction
as described in the Examples section, below.
[0011] FIG. 7 is a micrograph of a layered construction according
to the present disclosure, as described in the Examples section,
below.
[0012] FIG. 8 is a micrograph of a layered construction according
to the present disclosure, as described in the Examples section,
below.
DETAILED DESCRIPTION
[0013] The present disclosure relates in general to a surfacing
material to surface composite structures and methods of using
same.
[0014] The use of fiber reinforced resin matrix composite laminates
has become widely accepted for the variety of applications in
aerospace and automotive industries because their light weight,
high strength and stiffness. Weight reduction benefits and
performance enhancements are the biggest drivers behind
implementation of fiber reinforced resin matrix composite laminates
into industrial applications. Various airspace components being
manufactured from fiberglass and carbon fibers reinforced
composites including airplane fuselage sections and wing
structures. But being light and strong, composite structures are
not nearly as electrically conductive as previously widely utilized
aluminum structures. There is a need to provide adequate lightning
strike protection for composite structures. Composite structures
and in particular composite aircrafts what are not constantly
grounded must rely on a lightning protection system capable of
rapidly dissipate charge throughout the bulk of its structure as a
means of electrical energy dissipation. To prevent corrosion and
subsequent loss of conductivity, a metallic lightning strike
component may be encapsulated into surfacing film. The lightning
strike protection system has to be sufficiently conductive,
lightweight and durable. The durability of the lightning strike
protection system depends in great part on the reliability of the
surfacing polymer encapsulating the metallic component. Lightning
protection systems tend to experience bulk microcracking and
surface cracking due to the continuous changes in temperature,
humidity and pressure, differences in coefficients of thermal
expansion of different components, locked-in internal stresses,
less then ideal interfacial adhesion between metallic component and
surfacing polymer as well as continuous cyclical stresses on
various aircraft components. Microcracking and surface cracking may
make metallic component of a lightning protection system
susceptible to corrosion and subsequent loss of electrical
conductivity by allowing moisture penetration. Corrosion
deterioration of lightning strike protection can lead to increased
inspection time, increased maintenance time and cost and potential
compromise of aircraft safety. Microcracking and surface cracking
can extend into the surface finish producing visual defects on the
painted surfaces and further increase maintenance costs.
[0015] This disclosure demonstrates that the ability of the cured
composite articles with surfacing film according to the present
disclosure to resist microcracking is related to elastic (storage)
modulus (G') of the surfacing film. Elastic (storage) modulus (G')
may be tested by conventional methods, typically Rheometric Dynamic
Analyzer, torsion mode, as described in the Examples. Improved
microcracking resistance was found for the surfacing films
according to the present disclosure where the films are selected
such that the storage modulus of the composite bearing the
surfacing film is not greatly elevated compared to the storage
modulus of the bare composite. This selection may also be stated as
follows: the storage modulus for the composite with surfacing film
measured at 25.degree. C. [G'.sub.t25] is no more than 118% of the
storage modulus for the composite without surfacing film measured
at 25.degree. C. [G'.sub.s25], more typically no more than 115%,
more typically no more than 112%, in some embodiments no more than
110%, in some embodiments no more than 108%, in some embodiments no
more than 106%, and in some embodiments no more than 104%. This
selection may also be stated as follows: the storage modulus for
the composite with surfacing film measured at -54.degree. C.
[G'.sub.t-54] is no more than 118% of the storage modulus for the
composite without surfacing film measured at -54.degree. C.
[G'.sub.s-54], more typically no more than 115%, more typically no
more than 112%, in some embodiments no more than 110%, in some
embodiments no more than 108%, in some embodiments no more than
106%, and in some embodiments no more than 104%.
[0016] Any suitable polymeric composite may be used. Composites
useful in the present disclosure may comprise any suitable
reinforcement components, which may include metal, wood, polymer,
carbon particles or fibers, glass particles or fibers, or
combinations thereof, and may include any suitable matrix
component, which may include as polyester, vinyl ester, epoxy,
phenolic, polyimide, polyamide, polypropylene, PEEK, or other such
polymers or combinations thereof, and may optionally be made using
pre-preg materials.
[0017] Any suitable surfacing film may be used which meets the
storage modulus requirements recited herein. In some embodiments
the curable surfacing film comprises curable epoxy resin. In some
embodiments the curable surfacing film comprises a curable epoxy
resin which may optionally be a chain-extended epoxy resin. In some
embodiments the curable surfacing film comprises a core shell
rubber toughening agent. In some embodiments the curable surfacing
film comprises a urethane modified epoxy resin. In some embodiments
the curable surfacing film comprises a CTBN modified epoxy resin.
In some embodiments the curable surfacing film comprises a phenoxy
resin. In some embodiments the curable surfacing film comprises
micronized phenoxy resin. In some embodiments the curable surfacing
film comprises a phenolic hardener. Typically the resin excludes
phosphorus.
[0018] The composition of the curable surfacing film is typically
different from the composition of the curable matrix polymer of the
polymeric composite. The composition of the cured surfacing film is
typically different from the composition of the cured matrix
polymer of the polymeric composite.
[0019] In some embodiments the curable surfacing film comprises an
electrically conductive layer, typically a metal layer, which may
optionally be a foil, expanded foil, mesh, cloth, wires, or the
like.
[0020] The curable surfacing film may have any suitable thickness,
typically between 0.05 and 1.0 mm.
[0021] The layered construction may be made by any suitable method.
In some embodiments, a curable surfacing film and a curable
polymeric composite are laid up, in that order, in a tool having a
shape which is the inverse of the desired shape of the layered
construction the curable polymeric composite and curable surfacing
film are cured. In some embodiments, curing is accomplished with
application of heat. In some embodiments, curing is carried out
under sub-atmospheric pressure, typically less than 90% of one
atmosphere, more typically less than 50% of one atmosphere, and
more typically less than 10% of one atmosphere.
[0022] Objects and advantages of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention.
Examples Ex. 1-5 and Comparative Examples CEx. 1-5
[0023] Unless otherwise noted, all reagents were obtained or are
available from Aldrich Chemical Co., Milwaukee, Wis., or may be
synthesized by known methods.
Materials Used:
[0024] EPON.TM. 1004F: a medium molecular weight bisphenol A-based
polyepoxide resin having an epoxide equivalent weight of from 800
to 950 grams/equivalent, by Hexion Specialty Chemicals GmbH,
available from Resolution Performance Products, Houston, Tex.
D.E.H..TM. 85: Unmodified phenolic hardener having an active
hydrogen equivalent weight of from 250 to 280 grams/equivalent,
available from Dow Chemical Company, Midland, Mich. PAPHEN.RTM.
PKHP-200: micronized phenoxy resin, having a particle size of
<200 microns, available from Phenoxy Associates, Rock Hill, S.C.
USA. HYPOX.TM. M UA10: HyPox.TM. UA10 Urethane Modified Bisphenol A
Epoxy Resin, available from CVC Specialty Chemicals Inc.,
Moorestown, N.J., USA. HYPOX.TM. RA95: HyPox.TM. RA95 CTBN Modified
Bisphenol A Epoxy Resin, available from CVC Specialty Chemicals
Inc., Moorestown, N.J., USA. KANE ACE.RTM. MX 120: a 25%
concentrate of core shell rubber toughening agent in unmodified
liquid epoxy resin based on Bisphenol-A, available from Kaneka
Texas Corporation, 6161 Underwood Road, Pasadena Tex. 77507.
EPALLOY.RTM. 7200: A chemically modified bisphenol A diglycidyl
ether undiluted resin available from CVC Specialty Chemicals Inc.,
Moorestown, N.J., USA. AMICURE.RTM. CG-1400: Dicyandiamide curing
agent available from Air Products and Chemicals, Incorporated,
Allentown, Pa. OMICURE.TM. U-52: Aromatic substituted urea (4,4'
methylene bis(phenyl dimethyl urea)) used as a latent accelerator
for the dicyandiamide cure of epoxy resins, available from CVC
Specialty Chemicals Inc., Moorestown, N.J., USA. AF-555: 3M.TM.
Scotch-Weld.TM. Structural Adhesive Film AF-555 U 0.015, an
unsupported, thermosetting epoxy structural adhesive designed for
curing at temperatures of 300.degree. F. (149.degree. C.) to
350.degree. F. (177.degree. C.), available from 3M Company, St.
Paul, Minn. AF-191: 3M.TM. Scotch-Weld.TM. Structural Adhesive Film
AF-191 U 0.05, an unsupported, thermosetting, modified epoxy
designed for bonding composites, metal to metal and metal to
honeycomb components where high strength and peel at 350.degree. F.
(177.degree. C.), available from 3M Company, St. Paul, Minn.
AF-325: 3M.TM. Scotch-Weld.TM. Low Density Composite Surfacing Film
AF-325, Blue, 0.035, available from 3M Company, St. Paul, Minn.
FM.RTM. 300-2K: FM.RTM. 300-2K 0.08 red modified epoxy adhesive
film comprising a knit carrier for support available from Cytec
Engineered Materials Technical Service Havre de Grace, Md. 21078.
SYNSKIN.RTM. HC 9837.1: Epoxy-based composite surfacing film
designed to improve the surface quality of honeycomb stiffened
composite parts, comprising a non-woven fabric for support.
Available from Henkel Corporation, Aerospace Group, 2850 Willow
Pass Road, Bay Point, Calif. 94565 Liner: Siliconized kraft paper
available from Loparex, IowaCity, Iowa, USA, as product #23210 (76#
BL KFT H/HP 4D/6 MH paper 42''). Expanded Copper Foil: DEXMET.RTM.
3CU7-100A, 0.040 lb/ft.sup.2 (195.3 g/m.sup.2). Available from
Dexmet Corporation, 14 Commercial Street, P.O. Box 427, Branford,
Conn. 06405. Pre-Preg: A woven carbon fiber/epoxy resin composite
pre-preg material available from Critical Materials, Incorporated,
Poulsbo, Wash., as BMS 8-256, TYPE 4, CLASS 2, STYLE 3K-70-PW,
CYCOM.RTM. 970/PWC T300 3K VT 42''.
TABLE-US-00001 TABLE 1 Formulations. Component Ex. 1 Ex. 2 Ex. 3
Ex. 4 Ex. 5 CEx-1 CEx-2 CEx-3 CEx-4 CEx-5 EPON .TM. 1004F 15 15 15
15 10 AF-325 AF-555 AF-191 SYNSKIN .RTM. HC 9837.1 FM .RTM. 300-2K
KANE ACE .RTM. MX 120 15 10 10 10 15 EPALLOY .RTM. 7200 20 30 20 20
30 HYPOX .TM. UA10 0 0 5 0 0 HYPOX .TM. RA95 0 0 0 5 0 PAPHEN .RTM.
PKHP-200 5 5 5 5 5 D.E.H. .TM. 85 0 0 0 0 2.5 AMICURE .RTM. CG-1400
2.8 3.2 2.8 2.8 3.5 OMICURE .TM. U-52 1.5 1.5 1.5 1.5 1.5
Preparation of Resin Compositions
[0025] For Examples 1-5, the polyepoxide resins and flow modifier
(if applicable) indicated in Table 1 were charged into a 200 gram
capacity plastic container in the indicated ratios. The container
was heated for about 15 minutes in a forced air oven set at
125.degree. C., after which it was removed and placed in a
planetary-type mixer (SPEED MIXER.TM., Model DA 400 FV, available
from Synergy Devices Limited, Buckinghamshire, United Kingdom) set
at a speed of 2750 rpm for 1 minute. The container with the blend
of polyepoxide resins and flow modifier (if applicable) was then
returned to the oven and equilibrated at about 120.degree. C. for
between 15 and 20 minutes. Next, a toughening modifier was added to
the resin/modifier blend and it was mixed as described above, after
which the container was removed from the planetary mixer and
allowed to cool below 100.degree. C. The curing agents were then
added and the blend was mixed as described above. After removal
from the mixer, the inside wall of the container was scraped down
followed by putting the container back into the mixer for another
cycle. The resin composition obtained was used immediately to
prepare an uncured, Liner-supported surfacing film.
Preparation of Uncured, Liner-Supported Surfacing Films
[0026] The heated [90.degree. C./194.degree. F.] composition from
the "Preparation of Resin Compositions" procedure above was coated
between two 0.005 inch (0.13 millimeters) thick paper Liners, each
having a silicone release coating on one side and a polyethylene
coating on the opposite side, such that the surfacing film
contacted the silicone-coated side of each Liner. This was done
using a knife-over-bed coating station having a gap setting of
0.008 inches (0.20 millimeters) greater than the combined release
Liner thickness and a bed and knife temperature of 194.degree. F.
(90.degree. C.). A Liner supported surfacing film was obtained. The
Liner/surfacing film/Liner sandwich was stored for 24 hours at room
temperature (about 72.degree. F. (22.degree. C.)), then stored at
-20.degree. F. (-29.degree. C.) until further use.
Preparation of Laminates of Uncured Surfacing Film with
Incorporated Lightning Strike Protection (Expanded Copper Foil)
[0027] A sample of a Liner/surfacing film/Liner sandwich was
equilibrated at room temperature prior to use. The Liner from one
side of the sandwich, measuring about 11.5 inches (29.2
centimeters) long and about 6 inches (15.2 centimeters) wide, was
removed and Expanded Copper Foil was placed onto the exposed
surfacing film surface. Alternately, for comparative examples,
Expanded Copper Foil was placed onto an exposed surface of a
comparative surfacing film. This Expanded Copper Foil was slightly
larger in size than the sandwich. The Liner was replaced over the
Expanded Copper Foil and this lay-up was passed between two
rubber-coated, heated nip rollers at a temperature of approximately
140.degree. F. (60.degree. C.). The position of the upper roller
and its contact pressure with the lower drive roller was controlled
by air pressurized pistons having an air supply pressure of about
20 psi (137.9 kPa). A surfacing film having an Expanded Copper Foil
embedded therein and having a release Liner on each side was
obtained.
Preparation of Cured Polymeric Composite Articles with Surfacing
Film on One Outer Surface
[0028] With reference to FIG. 1, cured, woven carbon fiber
reinforced polymeric composite articles 10 having surfacing film 40
on one outer surface of a composite substrate 30 were made by the
following process. Three plies of carbon fiber Pre-Preg material,
measuring 4 inches by 4 inches (10.16 centimeters by 10.16
centimeters), were laid up one over another and a layer of a
surfacing film obtained as described in "Preparation of Uncured,
Liner-supported Surfacing Films" was positioned on the upper outer
major surface of the resulting construction. Alternately, for
comparative examples, a layer of a comparative surfacing film was
used. This lay-up was placed in a vacuum bag with surfacing film
directly against the tool surface which was then positioned in an
autoclave. A full vacuum of about 28 inches Hg was applied at room
temperature (approximately 72.degree. F. (22.degree. C.)) for 10 to
15 minutes after which the external pressure was gradually
increased to 55 psi (397 kPa). The vacuum bag was kept under full
vacuum (28 inches of Hg) for the duration of the cure cycle, and
the temperature was raised at 5.degree. F./minute (2.8.degree.
C./minute) up to 350.degree. F. (177.degree. C.) and held there for
2 hours. The cured polymeric composite article 10 with surfacing
film 40 on one surface was then cooled at 10.degree. F./minute
(5.5.degree. C./minute) to room temperature, at which point the
pressure was released, and the cured article having an approximate
thickness of 0.045 inches (0.114 mm) was removed from the autoclave
and vacuum bag.
Preparation of Cured Polymeric Composite Articles with Surfacing
Film with Incorporated Expanded Copper Foil on One Outer
Surface
[0029] With reference to FIG. 2, cured, woven carbon fiber
reinforced polymeric composite articles 20 having surfacing film 50
incorporating lightning strike protection in the form of an
Expanded Copper Foil 60 on one outer surface of a composite
substrate 30 were made by the following process. Three plies of
carbon fiber Pre-Preg material, measuring 4 inches by 4 inches
(10.16 centimeters by 10.16 centimeters), were laid up one over
another and a layer of surfacing film with incorporated Expanded
Copper Foil obtained as described in "Preparation of Laminates of
Uncured Surfacing Film with Incorporated Lightning Strike
Protection (Expanded Copper Foil)" was positioned on the upper
outer major surface of the resulting construction. This lay-up was
placed in a vacuum bag with surfacing film directly against the
tool surface which was then positioned in an autoclave. A full
vacuum of about 28 inches Hg was applied at room temperature
(approximately 72.degree. F. (22.degree. C.)) for 10 to 15 minutes
after which the external pressure was gradually increased to 55 psi
(397 kPa). The vacuum bag was kept under full vacuum (28 inches of
Hg) for the duration of the cure cycle, and the temperature was
raised at 5.degree. F./minute (2.8.degree. C./minute) up to
350.degree. F. (177.degree. C.) and held there for 2 hours. The
cured polymeric composite article (FIG. 2) with surfacing film on
one surface was then cooled at 10.degree. F./minute (5.5.degree.
C./minute) to room temperature, at which point the pressure was
released, and the cured article having an approximate thickness of
0.045 inches (0.114 mm) was removed from the autoclave and vacuum
bag.
Testing with Rain Erosion Simulator
[0030] The apparatus used to test for rain erosion resistance is
described in detail in U.S. Pat. Pub. No. 2008/0209981 A1 "Method
of Testing Liquid Drop Impact and Apparatus," the disclosure of
which is incorporated herein by reference.
[0031] The testing apparatus was assembled using a 0.177 caliber
air gun ("Drozd Air Gun", European American Armory Corporation,
Cocoa, Fla.,) and 1/2 inch (1.27 cm) diameter polyvinyl chloride
tube as the barrel section. 4.5 mm Grade II acetate pellets
(Engineering Laboratories, Inc, Oakland, N.J.) are propelled
through use of the pellet gun which is connected to a tank of
compressed nitrogen (Oxygen Service Company, St. Paul, Minn.) set
at about 60 psi (414 kPa). Samples are continuously coated with a
stream of water delivered through use of a water pump (Part No.
23609-170, VWR, West Chester, Pa.). Velocity of the pellets was
measured with a CED Millennium Chronograph, available from
Competitive Edge Dynamics LLC, Orefield, Pa.
[0032] The test specimens were machined on the diamond saw from
larger test panels prepared as described above. The samples were
tested by adhering approximately 0.5 inch by 0.5 inch (1.27 cm by
1.27 cm) specimens of Cured Polymeric Composite Articles with
Surfacing Film or Cured Polymeric Composite Articles with Surfacing
Film with Incorporated Expanded Copper Foil on one outer surface to
a round 304 stainless steel plate having an outer diameter of 7.6
cm and a central hole with a diameter of 0.35 cm. Test specimens
were positioned un-surfaced composite surface down to the stainless
steel substrate. 3M.TM. Scotch-Weld.TM. 2158 B/A two part adhesive
kit was used to adhere samples to the stainless steel substrate.
The adhesive used to adhere samples to the substrates was allowed
to cure on for 24 hours at 75.degree. F. (24.degree. C.) before
testing. The tests were conducted at a shot rate of 10 shots/sec.
The test results are shown in Tables 2 and 3.
TABLE-US-00002 TABLE 2 Simulated Rain Erosion Test Results for
Composite Surfacing Panels without incorporated Expanded Copper
Foil CEx-5 CEx-2 CEx-1 CEx-3 Ex-1 Ex-2 Ex-4 (FM .RTM. 300-2K)
(AF-555) (AF-325) (AF-191) (SF-1) (SF-2) (SF-4) no Cu no Cu no Cu
no Cu no Cu no Cu no Cu Total # 323 437 30 383 366 394 690 of shots
Average 456 453 459 459 461 453 455 velocity [ft/s] Crack No Crack
No No No No detected Crack detected crack Crack Crack Crack at 323
at 437 at 30 detected detected detected detected at 383 at 366 at
394 at 690
TABLE-US-00003 TABLE 3 Simulated Rain Erosion Test Results for
Composite Surfacing Panels with incorporated Expanded Copper Foil.
CEx-5 CEx-2 CEx-1 CEx-3 Ex-1 Ex-2 Ex-4 (FM .RTM. 300-2K) (AF-555)
(AF-325) (AF-191) (SF-1) (SF-2) (SF-4) with Cu with Cu with Cu with
Cu with Cu with Cu with Cu Total # 353 63 56 391 180 436 341 of
shots Average 450 463 453 458 458 453 451 velocity [ft/s] Crack
Copper Copper Crack Crack Crack No detected exposed exposed
detected detected detected crack at at 63 at 30 at at 180 at 436
detected 150. 180. at 341 Copper Copper exposed exposed at 353 at
391
[0033] Samples examination for crack detection was performed using
Bausch and Lomb variable (7.times. to 30.times.) magnification
optical microscope with external light source. The surfacing films
according to the present disclosure were shown to be more durable
than the comparative surfacing solutions, as evidenced by a higher
"Number of Shots before Crack is Detected."
[0034] FIG. 3 is a micrograph of a test sample of CEx-5 (FM.RTM.
300-2K) with Copper, after testing on the rain erosion simulator.
FIG. 4 is a micrograph of a test sample of CEx-3 (AF-191) with
Copper after testing on the rain erosion simulator. FIG. 5 is a
micrograph of a test sample of CEx-1 (AF-325) with Copper after
testing on the rain erosion simulator. FIG. 6 is a micrograph of a
test sample of CEx-2 (AF-555) with Copper after testing on the rain
erosion simulator. FIG. 7 is a micrograph of a test sample of Ex-1
(SF-1) with Copper after testing on the rain erosion simulator.
FIG. 8 is a micrograph of a test sample of Ex-4 (SF-4) with Copper
after testing on the rain erosion simulator.
Testing by Static Thermal Shock Exposure
[0035] Test specimens with approximate dimensions of 5.0 inch (12.7
cm) by 1.5 inch (3.8 cm) by 0.045 inch (0.114 cm) were machined on
the diamond saw from larger test panels prepared as described
above.
[0036] Five test specimens representing each example or comparative
example prepared as described above with incorporation of Expanded
Copper Foil were conditioned at 75.degree. F./ambient humidity for
seven days before being placed into the dual chamber thermal shock
oven where one chamber is capable of maintaining -67.degree. F.
(-54.degree. C.) and another chamber is capable of maintaining
180.degree. F. (80.degree. C.). Equilibration time at each
temperature was 10 minutes. 1000 hours of exposure time is achieved
in approximately seven days.
[0037] At the 1000 and 2000 hour marks one sample representing each
example or comparative example was removed from thermal shock
chamber and examined for microcracks. The remaining samples were
allowed to continue testing.
[0038] Samples examination for crack detection was performed using
the same microscope used for cracks detection of samples for rain
erosion simulation.
TABLE-US-00004 TABLE 4 Static thermal shock results 1000 h 2000 h
CEx-1 (AF-325) no cracks multiple cracks CEx-2 (AF-555) no cracks
multiple cracks CEx-3 (AF-191) no cracks multiple cracks CEx-4
(SYNSKIN .RTM. HC 9837.1) no cracks few cracks CEx-5 (FM .RTM.
300-2K) multiple cracks multiple cracks Ex-1 (SF-1) no cracks few
cracks Ex-2 (SF-2) no cracks no cracks Ex-3 (SF-3) no cracks no
cracks Ex-4 (SF-4) no cracks no cracks
Rheometric Dynamic Analyzer (RDA), Torsion Mode
[0039] Test specimens with approximate dimensions of 1.5 inch (3.8
cm) by 1/4 inch (0.635 cm) by 0.045 inch (0.114 cm) were machined
on the diamond saw from larger test panels prepared as described
above with incorporation of Expanded Copper Foil. In addition, a
test specimen of similar dimensions was prepared from only three
plies of cured woven carbon fiber reinforced composite without any
surfacing film on the outer surface. The samples were tested by
utilizing Rheometric Dynamic Analyzer using torsion method with a 1
Hz or 10 Hz frequency and 0.2% or 1.0% applied strain and at
isothermal conditions at 75.degree. F. (24.degree. C.) or
-67.degree. F. (-54.degree. C.). Testing at 10 Hz, 1.0% strain,
75.degree. F. (24.degree. C.) and -67.degree. F. (-54.degree. C.)
was conducted for the duration of two (2) hours. Testing at 1 Hz,
0.2% strain, -67.degree. F. (-54.degree. C.) was conducted for the
duration of twenty four (24) hours.
TABLE-US-00005 TABLE 5 Torsion RDA test results. 1 Hz 0.2% strain
10 Hz 1% strain 10 Hz 1% strain 24 h@ -54.degree. C. 2 h@
24.degree. C. 2 h@ -54.degree. C. CEx-1 (AF-325) multiple cracks 2
cracks multiple cracks CEx-2 (AF-555) no cracks no cracks 4 crack
CEx-3 (AF-191) no cracks no cracks 1 crack CEx-4 (SYNSKIN .RTM. HC
9837.1) no cracks 5 cracks multiple cracks CEx-5 (FM .RTM. 300-2K)
multiple cracks multiple cracks multiple cracks Ex-1 (SF-1) no
cracks no cracks no cracks Ex-4 (SF-4) no cracks no cracks no
cracks Ex-5 (SF-5) no cracks no cracks no cracks
[0040] Samples examination for crack detection after testing on RDA
in torsion mode was performed using Bausch and Lomb variable
(7.times. to 30.times.) magnification optical microscope with
external light source.
[0041] As evident from the data in the Table 5, microcracking
resistance of the surfacing films according to the present
disclosure was superior to the comparative examples.
[0042] Table 6 reports elastic (storage) modulus (G') data for
samples representing the examples and comparative examples. In the
RDA test methodology G' is defined as the elastic (storage)
modulus=cos .delta. (.tau./.gamma.) where .delta. is a phase angle
(phase shift between stress and strain vectors), .tau. is stress
and .gamma. is strain.
TABLE-US-00006 TABLE 6 Elastic (Storage) Modulus (G') Data for Bare
Cured Composite Substrate and Cured Polymeric Composite Articles
with Surfacing Film Incorporating Expanded Copper Foil Storage
Storage Modulus, Modulus, Storage Substrate Storage Substrate
Modulus, with Modulus, with Bare Surfacing Bare Surfacing Substrate
Film Substrate Film [G'.sub.s] [G'.sub.s + G'.sub.sr] G'.sub.s/
G'.sub.s/ (G'.sub.s + G'.sub.sr)/ (G'.sub.s + G'.sub.sr)/
[G'.sub.s] [G'.sub.s + G'.sub.sr] @-54.degree. C. @-54.degree. C.
G'.sub.s + G'.sub.sr G'.sub.s + G'.sub.sr G'.sub.s G'.sub.s
@25.degree. C. [Pa] @25.degree. C. [Pa] [Pa] [Pa] @25.degree. C.
@-54.degree. C. @25.degree. C. @-54.degree. C. CEx-1 (AF-325)
2.7E+09 3.4E+09 3.0E+09 4.0E+09 0.79 0.75 125% 133% CEx-2 (AF-555)
2.7E+09 3.5E+09 3.0E+09 3.9E+09 0.77 0.77 129% 130% CEx-3 (AF-191)
2.7E+09 3.3E+09 3.0E+09 3.7E+09 0.83 0.81 122% 123% CEx-4 (SYNSKIN
.RTM. 2.7E+09 3.2E+09 3.0E+09 3.8E+09 0.84 0.79 118% 126% HC
9837.1) CEx-5 2.7E+09 3.7E+09 3.0E+09 4.2E+09 0.73 0.71 137% 140%
(FM .RTM. 300-2K) Ex-1 (SF-1) 2.7E+09 3.1E+09 3.0E+09 3.4E+09 0.87
0.88 114% 113% Ex-2 (SF-2) 2.7E+09 3.0E+09 3.0E+09 3.3E+09 0.90
0.91 111% 110% Ex-3 (SF-3) 2.7E+09 2.9E+09 3.0E+09 3.2E+09 0.93
0.94 107% 106% Ex-4 (SF-4) 2.7E+09 2.8E+09 3.0E+09 3.1E+09 0.96
0.97 103% 103% Ex-5 (SF-5) 2.7E+09 3.0E+09 3.0E+09 3.3E+09 0.92
0.92 111% 110%
[0043] The ability of the cured composite articles with surfacing
film according to the present disclosure incorporating Expanded
Copper Foil on one outer surface to resist microcracking is related
to elastic (storage) modulus (G') of the surfacing film (in
particular, as tested by conventional methods, typically Rheometric
Dynamic Analyzer, torsion mode, as described above.) Improved
microcracking resistance was found for the surfacing films
according to the present disclosure, especially where the ratio of
storage modulus G'.sub.s for the three plies of composite substrate
without surfacing film to storage modulus G'.sub.s+G'.sub.sr for
the three plies of composite substrate with surfacing film with
incorporated lightning strike protection had a value of 0.85 or
more; i.e., microcracking resistance coefficient [C] was
.gtoreq.0.85.
C=G'.sub.s/(G'.sub.s+G'.sub.sr).gtoreq.0.85
[0044] This selection may also be stated as follows: the storage
modulus for the composite with surfacing film measured at
25.degree. C. [G'.sub.t25] is no more than 118% of the storage
modulus for the composite without surfacing film measured at
25.degree. C. [G'.sub.s25], more typically no more than 115%, more
typically no more than 112%, in some embodiments no more than 110%,
in some embodiments no more than 108%, in some embodiments no more
than 106%, and in some embodiments no more than 104%. This
selection may also be stated as follows: the storage modulus for
the composite with surfacing film measured at -54.degree. C.
[G'.sub.t-54] is no more than 118% of the storage modulus for the
composite without surfacing film measured at -54.degree. C.
[G'.sub.s-54], more typically no more than 115%, more typically no
more than 112%, in some embodiments no more than 110%, in some
embodiments no more than 108%, in some embodiments no more than
106%, and in some embodiments no more than 104%.
[0045] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and principles of this invention, and it should be
understood that this invention is not to be unduly limited to the
illustrative embodiments set forth hereinabove.
* * * * *