U.S. patent application number 13/175665 was filed with the patent office on 2011-10-27 for composite materials with improved performance.
This patent application is currently assigned to Hexcel Corporation. Invention is credited to Dana Blair, Maureen Boyle, Paul Mackenzie, David Tilbrook.
Application Number | 20110262630 13/175665 |
Document ID | / |
Family ID | 37435058 |
Filed Date | 2011-10-27 |
United States Patent
Application |
20110262630 |
Kind Code |
A1 |
Tilbrook; David ; et
al. |
October 27, 2011 |
Composite Materials With Improved Performance
Abstract
A composite material comprising at least one polymeric resin and
optionally at least one fibrous reinforcement where the polymeric
resin comprises at least one difunctional epoxy resin and at least
one epoxy resin with a functionality greater than two having at
least one meta-substituted phenyl ring in its backbone.
Inventors: |
Tilbrook; David; (Saffron,
GB) ; Blair; Dana; (Bourn Cambridge, GB) ;
Mackenzie; Paul; (Purley, GB) ; Boyle; Maureen;
(Castro Valley, CA) |
Assignee: |
Hexcel Corporation
Dublin
CA
Hexcel Composites Limited
Duxford
|
Family ID: |
37435058 |
Appl. No.: |
13/175665 |
Filed: |
July 1, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12441398 |
Mar 16, 2009 |
7972686 |
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PCT/GB2007/003741 |
Oct 2, 2007 |
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13175665 |
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Current U.S.
Class: |
427/121 ;
252/500; 252/511; 252/512; 252/513; 252/514; 427/386; 523/122;
524/539; 525/423; 977/700; 977/734; 977/742; 977/890 |
Current CPC
Class: |
Y10T 428/31515 20150401;
C08J 5/24 20130101; Y10T 428/31525 20150401; C08G 59/38 20130101;
Y10T 428/31511 20150401; C08L 63/00 20130101; C08G 59/5033
20130101; C08L 81/06 20130101; C08L 63/00 20130101; C08L 77/00
20130101; Y10T 428/31518 20150401; Y10T 428/24994 20150401; B29C
70/00 20130101; C08L 2666/02 20130101; Y10T 428/249924 20150401;
C08L 2205/03 20130101 |
Class at
Publication: |
427/121 ;
525/423; 524/539; 523/122; 252/500; 252/514; 252/512; 252/513;
252/511; 427/386; 977/734; 977/742; 977/700; 977/890 |
International
Class: |
B05D 3/10 20060101
B05D003/10; H01B 1/22 20060101 H01B001/22; B05D 5/12 20060101
B05D005/12; C08L 63/02 20060101 C08L063/02; H01B 1/24 20060101
H01B001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2006 |
GB |
0619401.3 |
Claims
1. A resin composition which is curable at a curing temperature,
wherein the resin composition comprises: from 10 to 40 weight
percent, based on the overall resin composition, of difunctional
epoxy resin; from 10 to 40 weight percent, based on the overall
resin composition, of triglycidyl-m-aminophenol; from 5 to 20
weight percent, based on the overall resin composition, of
insoluble thermoplastic particles; from 5 to 25 weight percent,
based on the overall resin composition, of thermoplastic toughening
agent; and a sufficient amount of a curing agent to provide curing
of said resin composition at said curing temperature.
2. A resin composition according to claim 1 wherein said
difunctional epoxy resin is selected from the group consisting of
diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A,
diglycidyl dihydroxy naphthalene and combinations thereof.
3. A resin composition according to claim 2 wherein the curing
agent comprises 4,4'-diaminodiphenyl sulphone and/or
3,3'-diaminodiphenyl sulphone.
4. A resin composition according to claim 1 wherein said insoluble
thermoplastic particles comprise polyamide.
5. A resin composition according to claim 1 wherein said
thermoplastic toughening agent comprises polyethersulfone.
6. A resin composition according to claim 5 wherein said insoluble
thermoplastic particles comprise polyamide.
7. A resin composition according to claim 2 wherein said insoluble
thermoplastic particles comprise polyamide.
8. A resin composition according to claim 7 wherein said
thermoplastic toughening agent comprises polyethersulfone.
9. A resin composition according to claim 1 wherein said resin
composition further comprises at least one additional ingredient
selected from flexibilisers, accelerators, thermoplastic polymers,
core shell rubbers, flame retardants, wetting agents, pigment/dyes,
ultra-violet absorbers, anti-fungal compounds, fillers and
conducting particles.
10. A resin composition according to claim 9 wherein said
conducting particles are selected from: silver, gold, copper,
aluminum, nickel, conducting grades of carbon,
buckminsterfullerene, carbon nanotubes, carbon nanofibers, nickel
coated carbon particles and silver coated copper particles.
11. A method of making a composite material comprising the steps
of: providing a resin composition according to claim 1 and at least
one fibrous reinforcement; and applying said resin composition to
said fibrous reinforcement.
12. A method according to claim 11 wherein said difunctional epoxy
resin is selected from the group consisting of diglycidyl ether of
bisphenol F, diglycidyl ether of bisphenol A, diglycidyl dihydroxy
naphthalene and combinations thereof.
13. A method according to claim 12 wherein the curing agent
comprises 4,4'-diaminodiphenyl sulphone and/or 3,3'-diaminodiphenyl
sulphone.
14. A method according to claim 11 wherein said insoluble
thermoplastic particles comprise polyamide.
15. A method according to claim 11 wherein said thermoplastic
toughening agent comprises polyethersulfone.
16. A method according to claim 11 wherein said resin composition
further comprises at least one additional ingredient selected from
flexibilisers, accelerators, thermoplastic polymers, core shell
rubbers, flame retardants, wetting agents, pigment/dyes,
ultra-violet absorbers, anti-fungal compounds, fillers and
conducting particles.
17. A method according to claim 16 wherein said conducting
particles are selected from: silver, gold, copper, aluminum,
nickel, conducting grades of carbon, buckminsterfullerene, carbon
nanotubes, carbon nanofibers, nickel coated carbon particles and
silver coated copper particles.
18. A method according to claim 11 which includes the step of
curing said resin composition.
Description
[0001] The present invention relates to composite materials with
improved performance, and particularly, but not exclusively, to
fibre reinforced composite materials.
[0002] Pre-impregnated (prepreg) composite materials based on
fibre-reinforcements comprise two primary constituents; a
continuous matrix, and reinforcing fibres. The composite materials
are often required to perform in demanding environments, such as in
the field of aerospace, and therefore physical limits and
characteristics of the composite are of critical importance. In
particular, when determining how light certain composite material
parts can be made, composite tensile strength and modulus are
important factors.
[0003] The tensile strength of a composite material is largely
dictated by the properties of the reinforcing fibre and the
fibre-resin volume ratio. In addition, composites which are in
tension tend to fail through a mechanism of accumulated damage
arising from multiple tensile breakages of the individual tow
filaments in the reinforcement. Once the stress levels in the resin
adjacent to the broken filament ends becomes too great, the whole
composite can fail. Therefore, fibre strength, the strength of the
matrix, and the efficiency of stress dissipation in the vicinity of
broken filament ends will contribute to the tensile strength of a
composite material.
[0004] In many applications, it is desirable to maximise the
tensile strength property of the composite material. However,
attempts to maximise tensile strength can often result in negative
effects in respect of other desirable properties, such as the
compression performance and damage tolerance of the composite
material.
[0005] The most common method of increasing composite tensile
performance is to change the surface of the fibre in order to
weaken the strength of the bond between matrix and fibre. This can
be achieved by reducing the amount of electro-oxidative surface
treatment of the fibre after graphitisation. Reducing the matrix
fibre bond strength introduces a mechanism for stress dissipation
at the exposed filament ends by interfacial debonding, which
provides an increase to the amount of tensile damage a composite
can withstand before failing in tension.
[0006] Alternatively, a coating or `size` can be applied to the
fibre which lowers resin-fibre bond strength. This approach is well
known in glass fibre composites, but can also be applied to carbon
reinforced composites. Using these strategies, it is possible to
achieve significant increases in tensile strength. However,
unfortunately the improvements are accompanied by a decrease in
properties such as compression after impact (CAI) strength, which
requires a high matrix-fibre bond strength.
[0007] An alternative approach is to use a lower modulus matrix.
Having a low modulus resin reduces the level of stress which builds
up in the immediate vicinity of broken filaments. This is usually
achieved by either selecting resins with an intrinsically lower
modulus (e.g. cyanate esters), or by incorporating an ingredient
such as an elastomer (carboxy-terminated butadiene-acrylonitrile
[CTBN], amine-terminated butadiene-acrylonitrile [ATBN] etc).
combinations of these various approaches are also known.
[0008] Selecting lower modulus resins can be effective in
increasing composite tensile strength. However, this can result in
a tendency to decrease compressive properties which require a stiff
resin, such as open hole compression strength or
0.degree.-compression strength.
[0009] The present invention seeks to provide a composite material
which has improved physical properties, such a tensile strength and
CAI strength, in comparison to prior attempts as described herein.
The present invention further seeks to provide a method of making
the composite material having improved physical properties.
[0010] The present invention also seeks to improve tensile strength
without causing substantial negative impacts upon other physical
characteristics of the composite material.
[0011] According to a first aspect of the present invention there
is provided a composite material comprising at least one polymeric
resin and optionally at least one fibrous reinforcement, wherein
the polymeric resin comprises; [0012] at least one difunctional
epoxy resin; and [0013] at least one epoxy resin with a
functionality greater than two having at least one meta-substituted
phenyl ring in its backbone.
[0014] According to a second aspect of the present invention there
is provided a method of making a composite material comprising the
steps of; [0015] providing a polymeric resin and at least one
fibrous reinforcement; and [0016] applying the polymeric resin to
the fibrous reinforcement; wherein the polymeric resin comprises at
least one difunctional epoxy resin, and at least one epoxy resin
with a functionality greater than two having at least one
meta-substituted phenyl ring in its backbone.
[0017] According to a third aspect of the present invention there
is provided a polymeric resin, wherein the polymeric resin
comprises; [0018] at least one difunctional epoxy resin; and [0019]
at least one epoxy resin with a functionality greater than two
having at least one meta-substituted phenyl ring in its
backbone.
[0020] It has been found that the selection and combination of the
components of the present invention results in a composite material
which has improved tensile strength and CAI strength in comparison
to conventional systems.
[0021] Additionally, it has surprisingly been found that the
benefits of improved tensile strength and CAI strength can be
obtained without substantially affecting the other desirable
physical properties of the resultant composite material (for
example matrix-fibre bonding, damage tolerance, stress dissipation,
compression performance etc.).
[0022] The observed increase in both CAI and tensile strength is
surprising and forms a basis of this invention.
[0023] Specifically, the use of a epoxy resin with a functionality
greater than two having at least one meta-substituted phenyl ring
in its backbone in place of the para-substituted glycidyl amine
resins, conventionally used in aerospace prepreg matrices, imparts
greater toughness to the composite material, as well as increasing
the base resin modulus. This gives rise to a step change in the CAI
performance. Surprisingly, the selected resins of the present
invention also impart very high tensile strength to the composite
material. Without wishing to be unduly bound by theory, it has been
postulated that the benefits of the invention are conferred due to
the greater translation characteristics.
[0024] The term polymeric resin as used herein refers to a
polymeric system.
[0025] The term "polymeric resin" and "polymeric system" axe used
interchangeably in the present application, and are understood to
refer to mixtures of chain lengths of resins having varying chain
lengths. The term polymeric therefore includes an embodiment where
the resins present are in the form of a resin mixture comprising
any of monomers, dimers, trimers, or epoxy resin having chain
length greater than 3. The resulting polymeric resin when cured
forms a crosslinked matrix of resin.
[0026] The polymeric resin may therefore be composed of 50-90 wt. %
resin in the form of monomer, 305 wt. % in the form of a dimes,
20-0.5 wt. % in the form of a trimer, and less than 20 wt. % in the
form of polymers of chain length greater than 3.
[0027] The difunctional epoxy resin may be any suitable
difunctional epoxy resin. It will be understood that this would
include any suitable epoxy resins having two epoxy functional
groups.
[0028] The difunctional epoxy resin may be saturated, unsaturated,
cylcoaliphatic, aromatic, alicyclic, or heterocyclic.
[0029] Difunctional epoxy resins, by way of example, include those
based on; diglycidyl ether of Bisphenol F, Bisphenol A (optionally
brominated), phenol and cresol epoxy novolacs, glycidyl ethers of
phenol-aldelyde adducts, glycidyl ethers of aliphatic diols,
diglycidyl ether, diethylene glycol diglycidyl ether, aromatic
epoxy resins, aliphatic polyglycidyl ethers, epoxidised olefins,
brominated resins, aromatic glycidyl amines, heterocyclic glycidyl
imidines and amides, glycidyl ethers, fluorinated epoxy resins, or
any combination thereof.
[0030] The difunctional epoxy resin may be preferably selected from
diglycidyl ether of Bisphenol F, diglycidyl ether of Bisphenol A,
diglycidyl dihydroxy naphthalene, or any combination thereof.
[0031] Most preferred is diglycidyl ether of Bisphenol F.
[0032] Diglycidyl ether of Bisphenol F is available commercially
from Huntsman Advanced Materials under the trade names Araldite
GY281 and GY285. Other examples of suitable commercially available
difunctional epoxy resins include Epikote and Epon which are
diglycidyl ethers of Bisphenol A and F, and are available
commercially from Hexion Specialty Chemicals of Columbus, USA.
[0033] The difunctional epoxy resin may be used alone or in any
suitable combination.
[0034] The difunctional epoxy resin may be present in the range 80
wt % to 0.1 wt % of the composite material. More preferably, the
difunctional epoxy resin is present in the range 70 wt % to 0.1 wt
%. Most preferably, the difunctional epoxy resin is present in the
range 40 wt % to 10 wt %.
[0035] The difunctional epoxy resin may be applied to the fibrous
reinforcement. The fibrous reinforcement may be fully or partially
impregnated by the difunctional epoxy resin. In an alternate
embodiment, the difunctional epoxy resin may be a separate layer
which is proximal to, and in contact with, the fibrous
reinforcement, but does not substantially impregnate said fibrous
reinforcement.
[0036] The epoxy resin with a functionality greater than two is a
compound comprising at least one meta-substituted phenyl ring in
its backbone. The epoxy resin may be any suitable epoxy resin. It
will be understood that this would include epoxy resins having an
epoxy group functionality eater than two.
[0037] Preferred epoxy resin components are those which are
trifunctional and tetrafunctional. Most preferably, the epoxy resin
components are those which are trifunctional.
[0038] A trifunctional epoxy resin will be understood as having
three epoxy groups substituted either directly or indirectly in a
meta orientation n the phenyl ring in the backbone of the
compound.
[0039] A tetrafunctional epoxy resin will be understood as having
four epoxy groups substituted either directly or indirectly in a
meta orientation on the phenyl ring in the backbone of the
compound.
[0040] It is also envisaged that the phenyl ring may be substituted
by other suitable non epoxy substituent groups. Suitable
substituent groups, by way of example, include hydrogen, hydroxyl,
alkyl, alkenyl, alkynyl, alkoxyl, aryl, aryloxyl, aralkyloxyl,
aralkyl, halo, nitro, or cyano radicals. The non epoxy substituent
groups may be straight, branched, cyclic, or polycylic
substituents.
[0041] Suitable non-epoxy substituent groups may be bonded to the
phenyl ring at the para or ortho positions, or bonded at a meta
position not occupied by an epoxy group.
[0042] Suitable tetrafunctional epoxy resins include
N,N,N',N'-tetraglycidyl-m-xylenediamine (available commercially
from Mitsubishi Gas Chemical Company under the name Tetrad-X, and
as Erisys GA-240 from CVC Chemicals).
[0043] Suitable trifunctional epoxy resins, by way of example, may
include those based upon phenol and cresol epoxy novolacs, glycidyl
ethers of phenol-aldelyde adducts, aromatic epoxy resins, aliphatic
triglycidyl ethers, dialiphatic triglycidyl ethers, aliphatic
polyglycidyl ethers, epoxidised olefins, brominated resins,
triglycidyl aminophenyls, aromatic glycidyl amines, heterocyclic
glycidyl imidines and amides, glycidyl ethers, fluorinated epoxy
resins, or any combination thereof.
[0044] The trifunctional epoxy resin may be triglycidyl meta
aminophenol.
[0045] Triglycidyl meta aminophenol is available commercially from
Huntsman Advanced Materials under the trade name Araldite MY0600,
and from Sumitomo under the trade name ELM-120.
[0046] The epoxy resin with a functionality greater than two having
at least one meta-substituted phenyl ring in its backbone may be
present in the range 80 wt % to 5 wt % of the composite material.
More preferably, the epoxy resin is present in the range 75 wt % to
5 wt %. Most preferably, the epoxy resin is present in the range 40
wt % to 10 wt %.
[0047] The epoxy resin with a functionality greater than two having
at least one meta-substituted phenyl ring in its backbone may be
applied to the fibrous reinforcement.
[0048] It will be understood that references to meta substituted
epoxy resin refers to those having a configuration about a phenyl
ring in the resin as shown in Figure 1.
##STR00001##
[0049] Where R.sup.1, R.sup.2, R.sup.3, and R.sup.4 represent
suitable non epoxy substituent groups substituted on the phenyl
ring. Suitable non epoxy substituent groups are as listed
hereinbefore. The non epoxy substituents R.sup.2, R.sup.3, and
R.sup.4 may be the same or independently selected.
[0050] Where E.sup.1 and E.sup.2 represent the epoxy backbone in
which the groups E.sup.1 and E.sup.2 are terminated or comprise an
epoxy group.
[0051] R.sup.1, R.sup.2, R.sup.3, and R.sup.4 may also represent
further epoxy groups in the embodiment where more than two epoxy
groups are bonded directly to the phenyl ring. In this embodiment,
it will be understood that the term meta substituted epoxy resin
refers to at least two of the epoxy groups E.sup.1 and E.sup.2
being bonded to the phenyl ring in a meta configuration with
reference to one another.
[0052] The fibrous reinforcement may be fully or partially
impregnated by the epoxy resin. in an alternate embodiment, the
epoxy resin may be a separate layer which is proximal to, and in
contact with, the fibrous reinforcement, hut does not substantially
impregnate said fibrous reinforcement.
[0053] The fibrous reinforcement of the composite material may be
selected from any fibrous material, including hybrid or mixed fibre
systems which comprise synthetic or natural fibres, or a
combination thereof. The fibrous reinforcement may preferably be
selected from any suitable material such as fibreglass, carbon or
aramid (aromatic polyamide) fibres.
[0054] The fibrous reinforcement is most preferably carbon
fibres.
[0055] The fibrous reinforcement may comprise cracked (i.e.
stretch-broken) or selectively discontinuous fibres, or continuous
fibres. It is envisaged that use of cracked or selectively
discontinuous fibres may facilitate lay-up of the composite
material prior to being fully cured, and improve its capability of
being shaped.
[0056] The fibrous reinforcement may be in a woven, non-crimped,
non-woven, unidirectional, or multiaxial textile structure
form.
[0057] The woven form may be selected from a plain, satin, or twill
weave style. The non-crimped and multiaxial forms may have a number
of plies and fibre orientations.
[0058] Such styles and forms are well known in the composite
reinforcement field, and are commercially available from a number
of companies, including Hexcel Reinforcements of Villeurbanne,
France.
[0059] The composite material may include at least one additional
multifunctional epoxy resin.
[0060] The additional multifunctional epoxy resin is a resin which
has an epoxy functionality of at least three, and is which does not
have a phenyl ring in the backbone having meta substituted epoxy
groups.
[0061] The multifunctional epoxy resin may be saturated,
unsaturated, cylcoaliphatic, aromatic, alicyclic, or
heterocyclic.
[0062] Suitable multifunctional epoxy resins, by way of example,
include those based upon phenol and cresol epoxy novolacs, glycidyl
ethers of phenol-aldelyde adducts, glycidyl ethers of dialiphatic
diols, ðylene glycol diglycidyl ether, aromatic epoxy
resins, dialiphatic triglycidyl ethers, aliphatic polyglycidyl
ethers, epoxidised olefins, brominated resins, aromatic glycidyl
amines, triglycidyl amino phenols, heterocyclic glycidyl imidines
and amides, glycidyl ethers, fluorinated epoxy resins, or any
combination thereof.
[0063] Specific examples of suitable multifunctional epoxy resin
include, by way of example,
N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl methane (TGDDM
available commercially as Araldite MY720 and MY721 from Huntsman
Advanced Materials, or ELM 434 from Sumitomo), triglycidyl ether of
para aminophenol (available commercially as Araldite MY 0500 or MY
0510 from Huntsman Advanced Materials), dicyclopentadiene based
epoxy resins such as Tactix 556 (available commercially from
Huntsman Advanced Materials), tris-(hydroxyl phenyl), and
methane-based epoxy resin such as Tactix 742 (available
commercially from Huntsman Advanced Materials).
[0064] Other suitable multifunctional epoxy resins include those
based upon phenol novolacs such as DEN 438 (from Dow Chemicals),
DEN 439 (from Dow Chemicals), or cresol novolacs such as Araldite
ECN 1273 (from Huntsman Advanced Materials), and Araldite ECN 1299
(front Huntsman Advanced Materials).
[0065] The multifunctional epoxy resins may be used alone or in any
suitable combination.
[0066] The multifunctional epoxy resin, if present, may be present
in the range 80 wt % to 0.1 wt % of the composite material. More
preferably, the multifunctional epoxy resin may be present in the
range 70 wt % to 0.1 wt %. Most preferably, the multifunctional
epoxy resin may be present in the range 40 wt % to 5 wt %.
[0067] The multifunctional epoxy resin may be applied to the
fibrous reinforcement. The fibrous reinforcement may be fully or
partially impregnated by the multifunctional epoxy resin. In an
alternate embodiment, the multifunctional epoxy resin may be a
separate layer which is proximal to, and in contact with, the
fibrous reinforcement, but does not substantially impregnate said
fibrous reinforcement.
[0068] The composite material may include insoluble thermoplastic
particles.
[0069] The term `insoluble thermoplastic particles` includes any
suitable material which is plastic and in a powder form, atomised
form, or particle form, prior to curing, and substantially
insoluble in the resin composition.
[0070] The term "particles" also includes fibres, flakes, rods, any
other three-dimensional particles, or any combination thereof.
[0071] The particles may have any suitable shapes including, by way
of example, fibrous, spherical, ellipsoidal, spheroidal, discoidal,
dendritic, rods, discs, acicular, cuboid or polyhedral.
[0072] The insoluble thermoplastic particles may have well defined
geometries or may be irregular in shape.
[0073] The insoluble thermoplastic particles may have a size
dispersion with at least 80% of the particles having a size in the
range 1 .mu.m to 100 .mu.m. Preferably, with at least 80% of the
additives having a size in the range 5 .mu.m to 70 .mu.m. Most
preferably, with at 80% of the additives having a sized in the
range 8 .mu.m to 60 .mu.m.
[0074] The insoluble thermoplastic particles may be polymers, winch
may be homopolymers, block copolymers, graft copolymers, or
terpolymers.
[0075] The insoluble thermoplastic particles may be thermoplastic
resins having single or multiple bonds selected from carbon-carbon
bonds, carbon-oxygen bonds, carbon-nitrogen bonds, silicon-oxygen
bonds, and carbon-sulphur bonds. One or more repeat units may be
present in the polymer which incorporate the following moieties
into either the main polymer backbone or to side chains pendant to
the main polymer backbone: amide moieties, imide moieties, ester
moieties, ether moieties, carbonate moieties, urethane moieties,
thioether moieties, sulphone moieties and carbonyl moieties.
[0076] The insoluble thermoplastic particles can also have a
partially crosslinked structure. The particles may be either
crystalline or amorphous or partially crystalline.
[0077] Suitable examples of insoluble thermoplastic particles
include, by way of example, polyamides, polycarbonates, polyacetal,
polyphenylene oxide, polyphenylene sulphide, polyarylates,
polyacrylates, polyethers, polyesters, polyimides, polyamidoimides,
polyether imides, polysulphones, polyurethanes, polyether
sulphones, and polyether ketones.
[0078] The insoluble thermoplastic particles may be selected from
polyamides.
[0079] It will be understood that the insoluble thermoplastic
particles selected from polyamides may be insoluble throughout the
process of making the composite material, and may be present in the
interleaf area of the composite material.
[0080] The insoluble thermoplastic particles may be chosen, by way
of example, from polyamide 6 (caprolactame--PA6), polyamide 12
(laurolactame--PA12), polyamide 11, polyurethane, polymethyl
methacrylate, crosslinked polymethyl methacrylate, densified
polyethylene sulphone, or any combination thereof.
[0081] Preferably, the insoluble thermoplastic particles are
selected from the following, either alone or in combination,
polyamide 6, polyamide 12, polyamide 11, or any combination
thereof.
[0082] Suitable insoluble thermoplastic particles include
commercially available polyamide powders from Arkema of France
under the trade name Orgasol.
[0083] The insoluble thermoplastic particle, if present, may be
present in the range 35 wt % to 0 wt % of the composite material.
Preferably, the insoluble thermoplastic particle may be present in
the range 35 wt. % to 0.1 wt. %. More preferably, the insoluble
thermoplastic particle may be present in the range 20 wt % to 5 wt
%. Most preferably, the insoluble thermoplastic particle may be
present in the range 15 wt % to 5 wt %.
[0084] Without wishing to be bound by theory, it is thought that
improvements in damage tolerance and in open hole tensile strength
were achieved by using different grades of insoluble thermoplastic
particles and mixtures thereof.
[0085] The insoluble thermoplastic particles may comprise a
copolymer blend of PA12 and PA6. The copolymer blend may comprise
PA6 in the range from 10 wt. % to 90 wt. %, and PA12 in the range
from 90 wt. % to 10 wt. %.
[0086] By using a copolymer of PA6 and PA12, it is possible to
obtain low modulus interleave without affecting the modulus of the
base resin, and additionally without compromising the overall water
resistance of the composite under wet conditions to the effects of
humidity.
[0087] The behaviour of the copolymer of PA6 and PA12 is different
in comparison with the standard PA6 grade due to their low melting
points. These particles will melt during cure and reform during
cooling down. The copolymer has a low level of crystallinity, and
induces a higher toughness improvement, which can be explained by a
higher level of crack pinning. The copolymers will deform in shear
just below the ILSS (Interlaminar Shear Strength) of the main resin
so the shear fracture will be delayed in the adjacent plies.
[0088] The addition of insoluble thermoplastic particles acts to
increase CAI performance of the composite material. To further
increase the CAI performance of the composite material, the
standard Orgasol (Orgasol 1002 DNAT1) was replaced by different
Orgasol grades. The grades selected were copolymers PA6 with PA12
with lower melting point in comparison with the T.sub.g (glass
transition temperature) of the resin. These grades have low level
of crystallinity, and will melt during the curing cycle and reform
in larger domains after cure in the interleave. This process will
generate a smoother and more gradual interface in comparison with
the interface created with Orgasol 1002 grade which is not affected
by the curing cycle. Orgasol 1002 DNAT 1 is a PA6 with a melting
point of 217.degree. C. These alternative grades can affect the
toughness of the interleave.
[0089] Suitable specific insoluble thermoplastic particles include,
by way of example, the following: [0090] Orgasol 3502 D NAT 1
(copolymer of 50% PA12 and 50% PA 6) with a melting point of
142.degree. C., particle size 20 microns [0091] Development grade
Orgasol CG199 (copolymer of 80% PA12 and 20% PA6) with a melting
point of 160.degree. C., particle size 20 microns and lower
molecular weight in comparison with commercial grades such as
Orgasol 1002 DNAT1 [0092] Orgasol 3801 DNAT1 (copolymer of PA12 and
PA6) with a melting point of 160.degree. C., particle size 20
microns and higher molecular weight than CG199 and comparable with
the Orgasol 1002 DNAT1 [0093] Orgasol 1002 D NAT1 (100% PA6) with a
melting point of 217.degree. C., particle size 20 microns
[0094] These insoluble thermoplastic particle Orgasol grades may be
used by themselves or in any combination.
[0095] The composite material may include at least one curing
agent.
[0096] The curing agents of the invention are those which
facilitate the curing of the epoxy-functional compounds of the
invention, and, particularly, facilitate the ring opening
polymerisation of such epoxy compounds; in a particularly preferred
embodiment, such curing agents include those compounds which
polymerise with the epoxy-functional compound or compounds, in the
ring opening polymerisation thereof.
[0097] Two or more such curing agents may be used in
combination.
[0098] Suitable curing agents include anhydrides, particularly
polycarboxylic anhydrides, such as nadic anhydride (NA),
methylnadic anhydride (MNA--available from Aldrich), phthalic
anhydride, tetrahydrophthalic anhydride, hexahydrophthalic
anhydride (HHPA--available from Anhydrides and Chemicals Inc.,
Newark, N.J.), methyltetrahydrophthalic anhydride (MTHPA--available
from Anhydrides and Chemicals Inc.), methylhexahydrophthalic
anhydride (MHHPA--available from Anhydrides and Chemicals Inc.),
endomethylenetetrahydrophthalic anhydride,
hexachloroendomethylenetetrahydrophthalic anhydride (Chlorentic
Anhydride--available from Velsicol Chemical Corporation, Rosemont,
Ill.), trimellitic anhydride, pyromellitic dianhydride, maleic
anhydride (MA--available from Aldrich), succinic anhydride (SA),
nonenylsuccinic anhydride, dodecenylsuccinic anhydride
(DDSA--available from Anhydrides and Chemicals Inc.), polysebacic
polyanhydride, and polyazelaic polyanhydride.
[0099] Further suitable curing agents are the amines, including
aromatic amines, e.g., 1,3-diaminobenzene, 1,4-diaminobenzene,
4,4'-diaminodiphenylmethane, and the polyaminosulphones, such as
4,4'-diaminodiphenyl sulphone (4,4'-DDS--available from Huntsman),
4-aminophenyl sulphone, and 3,3'-diaminodiphenyl sulphone
(3,3'-DDS).
[0100] Also, suitable curing agents may include polyols, such as
ethylene glycol (EG--available from Aldrich), polypropylene
glycol), and poly(vinyl alcohol); and the phenol-formaldehyde
resins, such as the phenol-formaldehyde resin having an average
molecular weight of about 550-650, the p-t-butylphenol-formaldehyde
resin having an average molecular weight of about 600-700, and the
p-n-octylphenol-formaldehyde resin, having an average molecular
weight of about 1200-1400, these being available as HRJ 2210,
HRJ-2255, and SP-1068, respectively, from Schenectady Chemicals,
Inc., Schenectady, N.Y.). Further as to phenol-formaldehyde resins,
a combination of CTU guanamine, and phenol-formaldehyde resin
having a molecular weight of 398, commercially available as CG-125,
from Ajinomoto USA Inc., Teaneck, N.J., is also suitable.
[0101] Yet further suitable resins containing phenolic groups can
be used, such as resorcinol based resins, and resins formed by
cationic polymerisation, such as DCPD--phenol copolymers. Still
additional suitable resins are melamine-formaldehyde resins, and
urea-formaldehyde resins.
[0102] Different commercially available compositions may be used as
curing agents in the present invention. One such composition is
AH-154, a dicyandiamide type formulation, available from Ajinomoto
USA Inc. Others which are suitable include Ancamide 400, which is a
mixture of polyamide, diethyltriamine, and triethylenetetraamine,
Ancamide 506, which is a mixture of amidoamine, imidazoline, and
tetraethylenepentaamine, and Ancamide 1284, which is a mixture of
4,4'-methylenedianiline and 1,3-benzenediamine; these formulations
are available from Pacific Anchor Chemical, Performance Chemical
Division, Air Products and Chemicals, Inc., Allentown, Pa.
[0103] Additional suitable curing agents include imidazole
(1,3-diaza-2,4-cyclopentadiene) available from Sigma Aldrich (St.
Louis, Mo.), 2-ethyl-4-methylimidazole available from Sigma
Aldrich, and boron trifluoride amine complexes, such as Anchor
1170, available from Air Products & Chemicals, Inc.
[0104] Still additional suitable curing agents include
3,9-bis(3-aminopropyl-2,4,8,10-tetroxaspiro[5.5]undecane, which is
commercially available as ATU, from Ajinomoto USA Inc., as well as
aliphatic dihydrazide, which is commercially available as Ajicure
UDH, also from Ajinomoto USA Inc., and mercapto-terminated
polysulphide, which is commercially available as LP540, from Morton
International, Inc., Chicago, Ill.
[0105] The curing agent (s) are selected such that they provide
curing of the resin component of the composite material when
combined therewith at suitable temperatures. The amount of curing
agent required to provide adequate curing of the resin component
will vary depending upon a number of factors including the type of
resin being cured, the desired curing temperature and curing time.
Curing agents typically include cyanoguanidine, aromatic and
aliphatic amines, acid anhydrides, Lewis Acids, substituted ureas,
imidazoles and hydrazines. The particular amount of curing agent
required for each particular situation may be determined by
well-established routine experimentation.
[0106] Exemplary preferred curing agents include
4,4'-diaminodiphenyl sulphone (4,4'-DDS) and 3,3'-diaminodiphenyl
sulphone (3,3'-DDS), both commercially available from Huntsman.
[0107] The curing agent, if present, may be present in the range 45
wt % to 5 wt % of the composite material. More preferably, the
curing agent may be present in the range 30 wt % to 10 wt %. Most
preferably, the curing agent may be present in the range 25 wt % to
15 wt %.
[0108] The composite material may also include additional
ingredients such as performance enhancing or modifying agents. The
performance enhancing or modifying agents, for example, may be
selected from flexibilisers, toughening agents/particles,
accelerators, the thermoplastic polymers and core shell rubbers,
flame retardants, wetting agents, pigments/dyes, UV absorbers,
anti-fungal compounds, fillers, conducting particles, and viscosity
modifiers.
[0109] The composite material may also comprise an accelerator
which is typically a urone. Suitable accelerators, which may be
used alone or in combination include N,N-dimethyl,
N'-3,4-dichlorphenyl urea (Diuron), N'-3-chlorophenyl urea
(Monuron), and preferably N,N-(4-methyl-m-phenylene
bis[N',N'-dimethylurea] (UR500).
[0110] Any suitable thermoplastic polymers may be used. Suitable
thermoplastic polymers for use with the present invention include
any of the following either alone or in combination: polyether
sulphone (PES), polyether ethersulphone (PEES), polyphenyl
sulphone, polysulphone, polyimide, polyetherimide, aramid,
polyamide, polyester, polyketone, polyetheretherketone (PEEK),
polyurethane, polyurea, polyarylether, polyarylsulphides,
polycarbonates, polyphenylene oxide (PPO) and modified PPO.
[0111] Toughening agents/particles may include, by way of example,
any of the following either alone or in combination: polyamides,
copolyamides, polyimides, aramids, polyketones,
polyetheretherketones, polyesters, polyurethanes, polysulphones,
high performance hydrocarbon polymers, liquid crystal polymers,
PTFE, elastomers, and segmented elastomers.
[0112] Other suitable toughening agents/particles may include
polycarbonates, polyacetal, polyphenylene oxide, polyphenylene
sulphide, polyarylates, polyacrylates, polyesters, polyethers,
polyamidoimides, polyether imides, polyether sulphones, and
polyether ketones.
[0113] The toughening agents/particles may be formed from polymers,
which may be homopolymers, block copolymers, graft copolymers, or
terpolymers.
[0114] The toughening agents/particles may be formed from
thermoplastic resins having single or multiple bonds selected from
carbon-carbon bonds, carbon-oxygen bonds, carbon-nitrogen bonds,
silicon-oxygen bonds, and carbon-sulphur bonds. One or more repeat
units may be present in the polymer which incorporate the following
moieties into either the main polymer backbone or to side chains
pendant to the main polymer backbone: amide moieties, imide
moieties, ester moieties, ether moieties, carbonate moieties,
urethane moieties, thioether moieties, sulphone moieties and
carbonyl moieties.
[0115] The toughening agents/particles can also have a partially
crosslinked structure. The structure may be either crystalline or
amorphous or partially crystalline.
[0116] Toughening agents/particles, if present, may be present in
the range 45 wt % to 0 wt % of the composite material. More
preferably, the toughening particles may be present in the range 25
wt % to 5 wt %. Most preferably, the toughening particles may be
present in the range 15 wt % to 10 wt %.
[0117] A suitable toughening agent/particle, by way of example, is
Sumikaexcel 5003P, which is commercially available from Sumitomo
Chemicals. Alternatives to 5003P are Solvay polysulphone 105P, or
the non-hydroxyl terminated grades such as Solvay 104P.
[0118] Without wishing to be bound by theory, it is postulated that
the toughening toughening agents/particles if present dissolve in
the resin, and upon curing phase separate. The toughening
agents/particles are thought to improve base resin toughness.
[0119] Suitable fillers may include, by way of example, any of the
following either alone or in combination: silicas, aluminas,
titania, glass, calcium carbonate, and calcium oxide.
[0120] Suitable conducting particles, by way of example, may
include any of the following either alone or in combination:
silver, gold, copper, aluminium, nickel, conducting grades of
carbon, buckminsterfullerene, carbon nanotubes and carbon
nanofibres. Metal coated fillers may also be used, for example
nickel coated carbon particles and silver coated copper
particles.
[0121] The composite material may comprise an additional polymeric
resin which is at least one thermoset resin.
[0122] The term `thermoset resin` includes any suitable material
which is plastic and usually liquid, powder, or malleable prior to
curing and designed to be moulded in to a final form. Once cured, a
thermoset resin is not suitable for melting and remoulding.
Suitable thermoset resin materials for the present invention
include, but are not limited to, resins of phenol formaldehyde,
urea-formaldehyde, 1,3,5-triazine-2,4,6-triamine (Melamine),
bismaleimide, vinyl ester resins, benzoxazine resins, phenolic
resins, polyesters, cyanate ester resins, epoxide polymers, or any
combination thereof. The thermoset resin is preferably selected
from epoxide resins, cyanate ester resins, bismaleimide, vinyl
ester, benzoxazine and phenolic resins.
[0123] The thermoset resin may be applied to the fibrous
reinforcement. The fibrous reinforcement may be fully or partially
impregnated by the thermoset resin. In an alternate embodiment, the
thermoset resin may be a separate layer which is proximal to, and
in contact with, the fibrous reinforcement, but does not
substantially impregnate said fibrous reinforcement.
[0124] It is understood that references to a composite material
include materials which comprise a fibre reinforcement, where the
polymeric resin is in contact with the fibre but not impregnated in
the fibre. The term composite material also includes an alternative
arrangement in which the resin is partially embedded or partially
impregnated in the fibre, commonly known in the art as prepreg.
[0125] The composite material formed may be in the form of
continuous tapes, towpregs, webs, or chopped lengths (chopping and
slitting operations may be carried out at any point after
impregnation). The composite material may be an adhesive or
surfacing film and may additionally have embedded carriers in
various forms both woven, knitted, and non-woven. The composite
material may be fully or only partially impregnated, for example,
to facilitate air removal during curing.
[0126] An example of a preferred composite material comprises
between about 22 wt % and 25 wt % Bisphenol-F diglycidyl ether;
between about 25 wt % and 30 wt % triglycidyl-m-aminophenol
(trifunctional epoxy resin); between about 17 wt % and 15 wt %
diaminodiphenylsulphone (either 3,3-DDS or 4,4-DDS as a curing
agent); between about 10 wt % and 15 wt % insoluble thermoplastic
particles, and between about 13 wt % and 17 wt % poly(ether
sulphone) as a toughening agent.
[0127] The composite material of the invention may be fully or
partially cured using any suitable temperature, pressure, and time
conditions known in the art.
[0128] Thus, according to a fourth aspect of the present invention
there is provided a method of making a cured composite material
comprising the steps of the second aspect, and curing the composite
material.
[0129] The curing step of the fourth aspect may be using any known
method. Particularly preferred are curing methods as described
herein.
[0130] The composite material may more preferably be cured using a
method selected from UV-visible radiation, microwave radiation,
electron beam, gamma radiation, or other suitable thermal or
non-thermal radiation.
[0131] The improved composite materials of the present invention
composites will find application in making articles such as
numerous primary and secondary aerospace structures (wings,
fuselage, bulkhead etc.), but will also be useful in many other
high performance composite applications including automotive, rail
and marine applications where high tensile strength, compressive
strength, and resistance to impact damage are needed.
[0132] Thus, according to a fifth aspect of the present invention
there is provided a process for preparing a cured composite
material containing article comprising the steps of: [0133] making
a cured composite material in accordance with the method of the
fourth aspect; and [0134] using the cured composite material to
produce an aerospace article.
[0135] The process of the fifth aspect may alternatively be a
method of making a cured composite material comprising the same
steps.
[0136] The curing step of the process or method of the fifth aspect
may be any known method. Particularly preferred are curing methods
as described herein.
[0137] All of the features described herein may be combined with
any of the above aspects, in any combination.
[0138] In order that the present invention may be more readily
understood, reference will now be made, by way of example, to the
following description.
[0139] It will be understood that all tests and physical properties
listed have been determined at atmospheric pressure and room
temperature. (i.e. 20.degree. C.), unless otherwise stated herein,
or unless otherwise stated in the referenced test methods and
procedures.
[0140] Primary structure composite material/prepreg performance is
probably best represented by other formulations which combine a
blend of difunctional and trifunctional para-substituted epoxy
resins toughened by the addition of poly(ethersulphone)
(Sumikaexcel 5003P PES) and cured by 4,4-diaminodiphenyl sulphone.
Additional damage tolerance is imparted by the addition of PA6
(Nylon-6) microparticles which serve to stop cracks propagating
through the interlaminar region.
[0141] Components used for the examples of the present invention
typically include those listed in Table 1. The formulation of Table
1 does not comprise an epoxy resin with a functionality greater
than two having at least one meta-substituted phenyl ring in its
backbone. Therefore, the formulation of Table 1 does not fall
within the scope of the invention and is included as a comparison
only.
TABLE-US-00001 TABLE 1 Formulation of comparison composite
material. Ingredient Comment GY 281 Bisphenol-F diglycidyl ether MY
0510 Trifunctional glycidyl amine MY 721 Tetrafunctional glycidyl
amine 4,4'-DDS or 3,3'-DDS Aromatic diamine curative Sumikaexcel
5003P PES Toughener Orgasol 1002 DNAT 1 Insoluble thermoplastic
particles
Effect of Formulation on Neat Resin Properties
[0142] Several formulations similar to the one shown in Table 1
were manufactured using MY 0600 (trifunctional epoxy resin with a
meta substituted phenyl ring) in place of MY 0510 and MY 721 (non
meta substituted multifunctional epoxy resins). These formulations
were manufactured and tested to determine compression, and using a
single-edged notch beam (SENB) tests to determine the resin
fracture energy under mode I loading.
[0143] Additionally, the Glc (adhesive fracture energy) and modulus
values for the composite materials made were determined. The
methods used to determine these values were as follows: [0144] The
Glc value represents the mode 1 adhesive fracture energy, and is
determined by SENB testing conducted according to American Society
for Testing and Materials (ASTM) testing standard E 399. [0145] The
bulk modulus is determined by compression on bars of resin of
dimensions 8 mm.times.16 mm.times.80 mm using the Boeing
antibuckling jig apparatus and test method ASTM D695.
[0146] The results obtained are summarised below:
TABLE-US-00002 TABLE 2 Resin fracture energy of formulations of
present invention. Formulations of Present invention Component A B
C D MY721 20.82 GY281 21.81 14.50 21.81 23.05 MY0600 1130 33.80
32.12 26.05 PES 5003P 13.81 14.00 13.81 15.00 4,4-DDS 18.94 24.20
18.94 7.01 3,3-DDS 15.39 Orgasol 1002 DNAT1 13.32 13.50 13.32 13.50
Modulus (GPa) 4.1 4.4 4.2 4.6 Glc (J/m.sup.2) 320 351 387 446
[0147] All amounts of components in Table 2 are expressed in tens
of wt. %.
[0148] The data in Table 2 shows that an increase of the
meta-substituted resin (i.e. using MY 0600 instead of epoxy resins
not containing at least one meta-substituted phenyl ring in its
backbone) along with thermoplastic insoluble particles (Orgasol
1002), provides significant and surprising increases in neat resin
toughness (Glc) at the same time as increasing resin modulus
(related to open hole compression).
[0149] Further formulations comprising MY0600 were prepared, and
these composite formulations are listed in Table 3.
TABLE-US-00003 TABLE 3 Formulations of composite materials of the
present invention. Batch No. 55035- Component 55012 55035 1A 1349
1351 65017 1312 4,4'-DDS 11.20 9.33 11.20 18.66 18.66 22.40 7.01
3,3'-DDS 11.20 9.33 11.20 -- -- -- 15.39 GY281 23.05 24.80 23.05
24.80 24.80 23.05 23.05 MY0600 26.05 28.03 26.05 28.03 28.03 26.05
26.05 PES 15.00 15.00 15.00 15.00 15.00 15.00 15.00 Orgasol 1002
13.50 13.50 13.50 13.50 13.50 13.50 13.50 Total 100 100 100 100 100
100 100
[0150] All the above formulations above used IM (intermediate
modulus) fibre at 268 gsm. All amounts of components in Table 3 are
expressed in terms of wt. %.
[0151] The composite properties of the compositions shown in of
Table 3 are listed in Table 4 and were determined as follows:
[0152] 0.degree. tensile modulus and strength were determined using
a 4 ply unidirectional laminates made of 268 gsm fibre areal weight
prepreg with 35% resin content in intermediate modulus fibre. The
laminate was cured for 2 hours at 180.degree. C. in an autoclave
and gave a nominal thickness of 1 mm. Consolidation was verified by
C-scan. The specimens were cut and tested in accordance with EN
2651. Results are normalised to 60% volume fractions based on
nominal cure ply thickness in accordance with EM 3783. [0153]
90.degree. tensile modulus and strength were determined using an 8
ply unidirectional laminate with 100/0/0 lay-up made of 268 gsm
fibre areal weight prepreg with 35% resin content in intermediate
modulus fibre. The laminate was cured for 2 hours at 180.degree. C.
in an autoclave and gave a nominal thickness of 2 mm. Consolidation
was verified by C-scan. The specimens were cut and tested according
to EN 2957. Results reported are actual strengths. [0154] In-plane
shear strength (IPS) and modulus were determined using an 8 ply
unidirectional laminate with 0/100/0 lay-up made of 268 gsm fibre
areal weight prepreg with 35% resin content in intermediate modulus
fibre. The laminate was cured for 2 hours at 180.degree. C. in an
autoclave and gave a nominal thickness of 2 mm. Consolidation was
verified by C-scan. The specimens were cut and tested according to
AITM 1.0002. Results quoted are not normalised. [0155] Interlaminar
shear strength (ILSS) was determined using an 8-ply laminate made
of 268 gsm fibre areal weight prepreg with 35% resin content and
intermediate modulus fibre. The laminate was cured for 2 hours at
180.degree. C. in an autoclave and gave a nominal thickness of 2
mm. Consolidation was verified by C-scan. The specimens were cut
and tested in accordance with EN 2563. Results reported are actual
strengths. [0156] Cross-ply interlaminar Shear Strength (X-PLY
ILSS) was determined using and 8 ply laminate with lay-up of
+45.degree./-45.degree. made of 268 gsm fibre areal weight prepreg
with 35% resin content and intermediate modulus fibre. The laminate
was cured for 2 hours at 180.degree. C. in an autoclave and gave a
nominal thickness of 2 mm. Consolidation was verified by C-scan.
The specimens were cut and test in accordance with EN 2563. Results
reported are actual strengths. [0157] Compression after impact
(CAI) was determined using the laminate in quasi isotropic lay-up,
16 plies of prepreg with 35% resin content with 25/50/25 lay-up and
268 gsm FAW (fibre area weight). The laminate is cured at
180.degree. C. for 2 hours in the autoclave, final laminate
thickness .about.4 mm. The consolidation was verified by c-scan.
The specimens were cut and tested in accordance with AITM 1.0010
issue 2, June 1994 [0158] Open hole compression (OHC) was
determined using a 20 ply laminate with 40/40/20 lay-up made of 268
gsm fibre areal weight prepreg with 35% resin content in
intermediate modulus fibre. The laminate was cured for 2 hours at
180.degree. C. in an autoclave and gave a nominal thickness of 5
mm. Consolidation was verified by C-scan. The specimens were cut up
and tested in accordance with Airbus test method AITM 1.00080.
Results quoted are values normalised to 60% volume fraction based
on nominal cure ply thickness with calculation carried out as per
EN 3784 method B. [0159] Open hole tensions (OHT) was determined
using a 20 ply laminate with 40/40/20 lay-up made of 268 gsm fibre
areal weight prepreg with 35% resin content in intermediate modulus
fibre. The laminate was cured for 2 hours at 180.degree. C. in an
autoclave and gave a nominal thickness of 5 mm. Consolidation was
verified by C-scan. The specimens were cut up and tested in
accordance with Airbus test method AITM 1.0008. Results quoted are
values normalised to 60% volume fraction based on nominal cure ply
thickness with calculation carried out as per EN 3784 method B.
[0160] The test methods referred to as EN 2651, EM 3783, EN 2957,
EN 2563, and EN 3784 are standardised tests used by Airbus
Industries.
[0161] Only batch 1312 was tested as prepreg. The table simply
serves to show that MY0600 increases toughness and modulus. The
batch 1312 formulation tested uses mostly 3,3'-DDS and gives the
highest modulus. It was expected that the batch 1312 formulation
would give the best compression performance and selected it for
testing on IM fibre.
[0162] Batch 1312 used a combination of 3,3'-DDS and 4,4'-DDS
dominated by the more reactive 3,3'-DDS with stoicheometry of
97%.
[0163] Batches 55012 and 55035-1A: also used a combination of
3,3'-DDS and 4,4'-DDS (but equal amount of each) with amine:epoxy
stoicheometry of .about.97%.
[0164] Batch 55035 used the same combination of amines as 55012 but
at lower stoicheometry (75%).
[0165] Batch 65017 used the only 4,4-DDS as the curative but still
at 97% stoicheometry.
TABLE-US-00004 TABLE 4 Composite properties data for formulations
of Table 3, all with fibre areal weight of 268 gsm and IM7 fibre
type with modified surface treatment. Property Units Value Batch
55012 55035 55035-1A 1349 1351 65017 1312 0.degree.-tensile modulus
GPa 22 dry 185 185 181 183 181 176 187 0.degree.-tensile strength
MPa 22 dry 2978 3119 3197 3030 2935 2875 3333 90.degree.-tensile
strength MPa 22 dry 44 64 60 90.degree.-tensile modulus GPa 22 dry
9 9 9 In-plane shear MPa 22 dry 103 97 97 90 114 106 92 strength
In-plane shear GPa 22 dry 5.50 5.50 5.31 5.20 5.30 5.70 5.30
modulus ILSS MPa 22 dry 95 92 90 92 89 99 95 ILSS MPa 70 dry 82 80
84 75 77 ILSS MPa 90 dry 76 72 69 72 ILSS MPa 120 dry 64 61 63 59
61 55 ILSS MPa 70 wet (eqm)* 70 68 71 72 CAI (25J) MPa 22 Dry 286
277 287 284 297 295 270 CAI 1 mm BVID MPa 22 Dry 188 209 226 225
227 208 206 OHT MPa 22 Dry 823 797 818 768 827 825 OHC MPa 22 Dry
402 410 421 402 418 423 406 OHC MPa 70 wet (eqm)* 292 310 324
[0166] The following observations for the composite material
formulations of Tables 3 may be made based on the data in Table 4:
[0167] Using MY0600, a trifunctional epoxy resin having a meta
substituted phenyl ring instead of epoxy resins not containing at
least one meta-substituted unsaturated phenyl ring in its backbone
gives tangible increases in: [0168] Open hole tensile strength
(OHT) [0169] CAI at 25J [0170] CAI at 1 mm barely visible impact
damage (BVID) impact energy [0171] Using MY0600 instead of epoxy
resins not containing at least one meta-substituted unsaturated
phenyl ring in its backbone improves: [0172] Open hole compression
(OHC) performance (see batches 55035-1A and 1351) [0173] In-plane
shear strength [0174] Using MY0600 instead of epoxy resins not
containing at least one meta-substituted unsaturated phenyl ring in
its backbone does not have a substantial negative impact upon:
[0175] 0.degree.-tensile strength and modulus [0176] In-plane shear
modulus [0177] ILSS at temperatures between -55.degree. C. and
120.degree. C.
[0178] The concurrent increase in OHT and CAI is surprising and
constitutes the basis for this invention disclosure.
[0179] In the context of the criteria cited above as being of
interest to primary structure composite applications, the specific
formulations of the present invention provide similar benefits.
However other additional factors may need to be taken into account
when selecting a specific formulation for commercialisation. These
additional factors include, for example, outlife and tack.
Additional Multifunctional Epoxy Resins
[0180] Further specific composite material formulations of the
present invention were prepared which comprise additional
multifunctional epoxy resins. These further formulations are shown
in Table 5.
TABLE-US-00005 TABLE 5 Formulations comprising additional
multifunctional epoxy resins. Batch/Material Designation Ingredient
HX1622 HX1622-3 HX1622-3A HX1622-4 Araldite 10.00 MY721 Araldite
7.77 7.36 MY0510 Araldite 26.05 20.00 18.96 25.00 MY0600 Araldite
23.05 GY281 Araldite 24.55 23.27 16.54 GY285 PES 15.00 15.00 15.00
15.00 Orgasol 13.50 13.50 13.50 13.50 1002N 4,4' DDS 22.40 19.18
21.91 19.96
[0181] All amounts of components in Table 5 are expressed in terms
of wt. %.
[0182] The composite physical properties of the formulations listed
in table 5 are listed in Table 6. The composite physical properties
were determined as follows: [0183] All materials were tested per
BMS8-276, which is the Boeing test method for primary structure
composite materials. The BMS 8-276 is similar to the Airbus
standard AIMS 05-01-002 which cites many of the Airbus Industries
Test Methods (AITM) used for generation of the text data, but uses
different test methods, and also different lay-up and sample
dimensions. [0184] The composite properties were generated using
268 gsm fibre areal weight prepreg with a resin content of 35%.
TABLE-US-00006 [0184] TABLE 6 mechanical data for formulations of
Table 5. Material Designation HX1622 HX1622-3 HX1622-3A HX1622-4
Fibre Type IM7 IM7 mod IM7 IM8 IM7 AS7 IM8 IM7 OHT 510 518 503 516
504 400 483 516 Strength RT (MPa) CAI 346 296 363 347 332 311 337
323 Strength (C1.1) in-lb (MPa)
[0185] It should be noted that IM7 fibre is IM fibre with a lower
surface treatment level.
Insoluble Thermoplastic Particles
[0186] By using different interleave particles, performance can be
further enhanced by further selection of insoluble thermoplastic
particles.
[0187] The development continued to improve the hot/wet performance
of 3502 and 1002 combination, and by using a higher molecular grade
of CG199 called 3801 DNAT1, both described hereinbefore. The
formulations which were prepared are detailed in Table 7.
TABLE-US-00007 TABLE 7 Formulations for different interleave
particles (Orgasol grades). Batch Batch Batch Batch Batch Component
1349 & 1351 1350 & 1352 1347 1348 1369 GY281 24.80 24.80
24.80 24.80 26.19 MY0600 28.03 28.03 28.03 28.03 29.6 PES 5003P
15.00 15.00 15.00 15.00 15.00 4,4'-DDS 18.66 18.66 18.66 18.66
19.70 Orgasol 1002 13.50 6.75 4.75 DNAT1 Orgasol 3502 6.75 13.5
4.75 DNAT1 CG 199 13.5 Develop- ment grade
[0188] All amounts of components in Table 7 are expressed in terms
of wt. %.
[0189] Table 8 shows the composite physical properties for the
composites of Table 7. The values contained in Table 8 were
calculated and determined as discussed previously with reference to
Table 4.
TABLE-US-00008 TABLE 8 Composite physical properties on IM7 fibre
with surface modified treatment, 35% resin content, FAW 268 gsm
Batch 1349- Batch 1352 Batch 1347 Batch 1348 Test Tst Temp 1351 #
(3502/1002) (3502) (CG199) 0.degree. Tensile Strength MPA (dry)
RT/dry 3310-3350 3086 0.degree. Tensile Modulus GPa (dry) RT/dry
186-196 181 70.degree. C./wet 70.degree. C./wet ILSS MPa RT/dry
94.6 85 88 71.5 70.degree. C. 82.2 75 69.2 61.1 90.degree. C. 75.5
69 59.4 56 120.degree. C. 64 56 45,8 48.8 Wet 70.degree. C. 69.9 67
51 IPS Strength, MPa RT/dry 103 116 100.2 70 IPS Modulus, GPa
RT/dry 5.5 5.0 4.59 4.31 Open Hole Tensile Strength MPa RT/dry 823
831 814 1070 (lay up 40/40/20) Open Hole Compression Strength MPa
RT/dry 402 415 394 393 (lay up 40/40/20) 70.degree. C./wet 292 280
252 274 CAI MPa after 25 J impact RT/dry 286-293 340 307.6 243 30 J
274-289 281 222.45 40 J 226-255 245.6 176 1 mm BVID 185-188 237 202
Not reached # The range data was obtained using batches 1349 and
1351.
[0190] The following observations can be made from the data of
Table 8: [0191] Using Orgasol 3502 in combination with Orgasol 1002
gives tangible increases in: [0192] CAI at 25J [0193] CAI at 1 mm
barely visible impact damage (BVID) impact energy [0194] OHT [0195]
The combination Orgasol 3502 with 1002 works better in comparison
with 3502 as single grade: [0196] A reduction in ILSS and hot/wet
OHC were recorded [0197] Using Orgasol CG 199 in place of Orgasol
1002 had an unexpected effect on OHT: [0198] A high OHT value
recorded for this grade [0199] Low CAI values were recorded due to
lower particle's molecular weight
[0200] A further compositions using a combination of PA-particles
as interleaf was prepared and is listed in Table 9.
TABLE-US-00009 TABLE 9 Composite material formulation with
different Orgasol combinations. Component Batch 1368 4,4-DDS 18.66%
GY281 24.81% MY0600 28.03% 5003P PES 15.00% Orgasol 1002 6.75%
Orgasol 3801 DNAT1 6.75% Total wt % 100%
[0201] The formulation listed in Table 9 was then used along with
the formulations listed in Table 7 (i.e. Batches 1347, 1348, 1350,
1352, and 1369), and the physical properties of these composites
were determined. The physical properties are listed in Table
10.
[0202] The composite physical properties in Table 10 were
determined using the same methods as described with reference to
Table 4.
TABLE-US-00010 TABLE 10 Composite physical property results for
formulations of Table 9 and 4. Fibre T800S IM7 with modified
surface treatment FAW (gsm) 268 268 268 268 268 268 268 Resin
content % 35% 35% 35% 35% 35% 35% 35% Test Temp T800 Test Unit
(.degree. C.) Batch Qual 1347 1348 1350 1352 1369 1368
0.degree.-tensile modulus GPa 22 dry 169 -- -- 181 181 -- --
0.degree.-tensile Strength MPa 22 dry 2845 -- -- 3089 3086 -- --
In-plane shear strength MPa 22 dry 78.2 100.2 70 103 116 117 97
In-plane shear modulus GPa 22 dry 4.98 4.59 4.31 5.00 5.00 4.90
4.90 ILSS MPa 22 dry 90.1 88 71.5 91 85 94 84 ILSS MPa 70 dry 69.2
61.1 73 75 -- 84 ILSS MPa 90 dry 70.3 59.4 56 67 69 72 60 ILSS MPa
120 dry 60.5 54.8 48.8 53 56 61 52 ILSS MPa 70 wet (eqm)* 65 51 67
67 62 58 CAI (25J) MPa 22 dry 253 308 243 296 340 333 326 CAI (30J)
281 222 -- -- -- -- CAI (40J) 246 176 -- -- -- -- CAI 1 mm BVID MPa
22 dry 0 202 not reached 238 237 233 OHT MPa 22 dry 713 814 1070
817 831 -- -- OHC MPa 22 dry 383 394 393 394 415 399 375 OHC MPa 70
wet (eqm)* 328 252 274 287 280 290 292
[0203] Table 10 shows that a preferred composite would comprise
thermoplastic particles Orgasol 3801 DNAT1 in combination with
Orgasol 1002 (standard grade). This provided a better hot/wet
retention and ILSS performance without a negative impact on the
other mechanical characteristics.
[0204] It is to be understood that the invention is not to be
limited to the details of the above embodiments, which are
described by way of example only. Many variations are possible.
* * * * *