JPH051159A - Fiber-reinforced composite material reinforced with porous resin particles - Google Patents

Abstract

PURPOSE: To provide a fiber-reinforced composition reinforced with porous resin articles useful for the production of fiber-reinforced composite bodies.

CONSTITUTION: A laminated fiber-reinforced composite body comprises an epoxy matrix resin composition and continuous structural fibers embedded in the matrix resin and is formed of a plurality of layers, each individual layer being composed of the structural fibers forming a layer of a spherical spongy structure and porous hard polyamide particles having an average particle diameter of about 1-about 75 microns which are dispersed in the matrix resin.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to composite materials, and in particular tough, impact resistant fiber reinforced composites. More specifically, the present invention relates to methods of reinforcing fiber-reinforced composites and particles useful in reinforcing such composites.

[0002]

BACKGROUND OF THE INVENTION Fiber reinforced composites are widely accepted high strength, high modulus materials for use in sports equipment and in the manufacture of consumer products such as home appliances. Also,
Composites are increasingly used as structural components for automobiles and as components for building and aircraft. When used in structural applications, composites are typically formed by embedding continuous fiber filaments or woven fabrics in a thermosetting or thermoplastic resin matrix. Such composites can exhibit considerable strength and stiffness, and the possibility of achieving significant weight savings makes them extremely attractive for use as metal substitutes. However, acceptance for many structural applications has been limited by the many vulnerabilities of currently available composite materials. The inability of such composites to withstand impact while retaining useful tensile and compressive strength has been a serious problem for many years. The low impact resistance of composites can usually be achieved by using large amounts of composites. However, this solution increases costs, reduces the weight savings that would otherwise be achievable, and makes them unacceptable for many applications.

The composite industry has long been deeply involved in finding ways to overcome these drawbacks. Significant efforts have been expended over the last two decades towards developing composites with improved fracture toughness. Since most of the commonly used matrix resins as well as many of the reinforcing fibers are generally brittle, much of that effort has been devoted to work to obtain components with good toughness. As a result, research into toughened matrices has been the subject of many recent patent documents.

For decades, rubber modifiers have been used in the plastics industry to reinforce rigid and sometimes brittle thermoplastic and thermoset engineering resins. In most cases, the rubber is dispersed throughout the rigid resin in the form of particles. Also, various means have been developed to modify the interaction between the rubber particles and the rigid phase to improve the effectiveness of the rubber component. For example, the rubber component has been modified by grafting to modify its compatibility with the rigid phase, and it is effective to add reactive functional groups to the rubber to facilitate binding to the rigid phase. It is also shown. Other solutions have included the combination of different resins, the formation of blends and alloys with improved properties.

The method used to reinforce engineering resins is described by Diamant and Moulton in "Develop.
ment of Resin for Damage Tolerant Composites
-A Systematic Approach "(29th National S
As shown in AMPE Symposium, April 3-5, 1984), it has been adapted to strengthen matrix resins commonly used in composite structures. Also, 1973 2
Forming alloys and blends by adding a more ductile thermoplastic resin such as polysulfone to an epoxy resin composition in accordance with British Patent No. 1,306,231 published on May 7, improves ductility of the epoxy resin. And has been shown to provide improved toughness. More recently, the combination of epoxy resins and end-functionalized thermoplastics has been shown to exhibit improved toughness (see US Pat. No. 4,498,948). Most recently, curable compositions of epoxy resins and thermoplastics with reactive terminal functional groups have been said to improve the toughness of specially formulated matrix resins, provided that the pure resin is After curing, the crosslinked glass phase exhibits the particular phase separation morphology dispersed in the glass continuous phase (US Pat. No. 4,656,208).
No.). Also, include a reactive rubber component (
This is said to be included in the cross-linked dispersed glass phase) and further improvement is said to be achieved (see US Pat. No. 4,680,076).
. Most recently, it has been proposed to use infusible particles made from rubber dispersed in a phase separated crosslinked epoxy resin to reinforce such matrix resin based composites (US Pat. 4,783,506).

Although the addition of rubber, thermoplastic resin, etc. generally improves the ductility and impact resistance of the pure resin, the effect on the resulting composite is not always beneficial. In many cases, the toughness enhancement of the composites is negligible and the resistance to environmental extremes such as reduced high temperature properties and exposure to water at elevated temperatures is often seen. Composite structures that rely on unique resin morphologies that are difficult to reproduce in complex manufacturing processes or to achieve improved toughness may require impractical degrees of control during fabrication, thus It increases manufacturing costs and sometimes results in unstable performance and poor reliability.

Another method for making a reinforced composite is:
Japanese Patent Application No. Sho 49-132, published on May 21, 1976
No. 669, it was the development of a laminated composite structure in which layers of fibers embedded in a matrix resin and layers of a thermoplastic resin were alternated. Recently, U.S. Pat. No. 4,604,319 discloses a laminated fiber-resin composite in which a thermoplastic resin layer is adhesively bonded and interposed between a plurality of fiber-reinforced matrix resin layers. Interleaf structures are usually manufactured by impregnating continuous fibers with resin to form a prepreg and then alternating the prepreg with a sheet of thermoplastic resin film to deposit the composite. The deposited structure is then subjected to heat and pressure, thus curing the matrix resin and bonding the layers together. This patent also discloses an interleaf layer formed by filling a thermoplastic resin with a reinforcing material such as chopped fibers, solid particles and whiskers.

Although interleaved composite structures having improved toughness have been disclosed, some other physical properties have been sacrificed, including decreased glass transition temperature and increased high temperature creep. Yet another difficulty associated with such composites is the loss of stiffness in many such composites, possible adhesive failure between layers formed of different resins, and poor solvent resistance during use. Characteristic deterioration can be mentioned. In addition, thermoplastic-based prepregs generally lack tack, which complicates their fabrication into composites and is required for fabrication of complex structures. Increase the degree of skill. In the end, this can lead to increased scrap losses and the need for more complex quality control operations, leading to increased manufacturing costs to obtain acceptable reliability levels.

Recently, it has been proposed to use infusible particles made of rubber dispersed in a phase separated crosslinked epoxy resin matrix for the reinforcement of such matrix resin based composites. (US Patent No. 4,
783,506). It is also disclosed in the art to disperse hard particulate modifiers in a matrix resin for reinforcement of composite materials, which
For example, European Published Patents 274,899 and 351,025 and US Pat. No. 4,863,78.
No. 7, see them if necessary.

Thus, the compositions and methods currently available for making reinforced composites require further improvement. Composites with improved impact resistance, especially those with good compressive strength after impact, represent a valuable advance in the art,
And a reliable method for producing such reinforced composites would be quickly accepted and could thus replace the complex and costly production methods currently available for these purposes. .

[0011]

SUMMARY OF THE INVENTION The present invention is a laminated composite structure comprising continuous fibers and a matrix resin composition, and more specifically, a composite formed by embedding continuous fibers in a matrix resin reinforced with a particulate modifier. An improved laminated composite structure characterized by the use of a particulate modifier (also described as porous polyamide particles) having an essentially spherical sponge-like structure, and laminating prior to curing Provided is a method for making a reinforced laminated composite by incorporating porous polyamide particles in a matrix resin that is spaced between intermediate layers of the composite. The resulting composite structure exhibits a significant and unexpected improvement in toughness.

[0012]

Detailed Description of the Invention The improved composite structure of the present invention comprises separate layers formed by embedding continuous fibers in a matrix resin, which layers are essentially spherical sponge-like. They are separated or usually separated by a layered region or layers of matrix resin filled with finely divided polyamide resin (also referred to as porous polyamide particles) in the form of structured particles.

Matrix resins useful in making reinforced composites in accordance with the practice of the present invention are resin compositions commonly used in the fiber reinforced composite industry and include both thermosets and thermoplastics. be able to.
However, thermosetting resins are preferred for most applications, and thermosetting resins described as useful in the practice of the present invention include epoxy resins, cyanate resins, bismaleimide resins, cyanate resin components. And the bismaleimide resin component in combination with BT resins and mixtures of such resins as well as those most commonly used in the production of fiber reinforced composites such as the widely used crosslinkable polyester resins. Many thermosetting resins generally have low ductility and are therefore extremely brittle, and therefore composite structures based on such resins will greatly benefit when reinforced according to that teaching.

Thus, preferred matrix resin compositions are based on thermosetting resins, and particularly preferred are the well known and widely used epoxies which generally contain suitable curing agents such as epoxy resins and diamine curing agents. It is a resin composition. The epoxy resin composition may optionally include suitable cure accelerators and additional components such as are commonly used in the thermoset composite industry.

The epoxy resin which can be used is a curable epoxy resin having a plurality of epoxy groups per molecule. Such resins are commonly used to make composite materials, and many are readily available from commercial sources. Examples of such resins are polyglycidyl compounds including reaction products of polyfunctional compounds such as alcohols, phenols, carboxylic acids, aromatic amines or aminophenols with epichlorohydrin, epoxidized dienes or polyenes. Still other examples include diglycidyl ethers of diene-modified phenolic novolacs, reaction products of polyfunctional cycloaliphatic carboxylic acids with epichlorohydrin, cycloaliphatic epoxides, cycloaliphatic epoxy ethers and cycloaliphatic Examples thereof include cycloaliphatic epoxides such as epoxy ester. It is also possible to use mixtures of epoxy resins. Preferred epoxides include bisphenol A epoxides, epoxy novolacs, cycloaliphatic epoxy ethers and glycidyl amines. A variety of these epoxy resins are available from commercial sources such as "PGA-X" from Sherwin Williams Company, "DEN431" and "Tactix 56" from Dow Chemical Company, "Glyamine 125" from FIC Corporation and Ciba. Available from Geigy Corporation under trade names such as "RD87-160" and "MY-720".

Diamine curing agents that can be used include aromatic diamines commonly used in the production of epoxy resins,
For example, 4,4 ^'- diaminodiphenyl ether, 4,
4 ^'- diaminodiphenylmethane, ^4,4' - diaminodiphenyl sulfone, 3,3 ^'- diaminodiphenyl sulfone, p- phenylenediamine, m- phenylenediamine, ^4,4' - bis (diamino diphenyl) propane,
4,4 ^'- diaminodiphenyl sulfide, trimethylene glycol bis (p- aminobenzoate), etc. and various positional isomers thereof. Variants of polynuclear aromatic diamine hardeners such as US Pat. No. 4,579,88
No. 5, No. 4,517, 321 and No. 4,686,
No. 250, as well as xylene diamine,
Bis (aminomethyl) cyclohexane, dicyandiamide and the like are also useful. Various diamine curing agents can be used alone or in combination.

Suitable epoxy resin compositions can be prepared according to methods and practices well known and widely used in the resin industry. Generally, the matrix resin composition comprises more than 2 parts by weight (pbw) diamine curing agent per 100 parts by weight epoxy resin. The particular level of curing agent selected will depend on the type of diamine used, but is preferably at least 3 pbw per 100 pbw epoxy resin, more preferably from about 6 to about 150 pbw.
Diamine hardeners are used. The amount of each component selected depends on the molecular weight of the individual components and the desired molar ratio of reactive amine (N—H) groups to epoxy groups in the final matrix resin system. For most prepreg and composite applications, about 0.3: 1 to 1.8: 1, preferably 0.4: 1.
Sufficient diamine hardener is used to provide a molar ratio of NH groups to epoxide groups in the range of 1.3: 1.

The composition may further include a thermoplastic polymer to impart improved toughness to the resulting composite by improving the ductility and impact resistance of the cured resin composition. When dissolved in the composition prior to curing, the thermoplastic polymer can also improve the viscosity and film strength of the uncured resin, thereby improving resin processability for use in the impregnation operation, and Prepregs can be provided with good handling properties for use in the manufacture of composites. Various thermoplastics for use in combination with epoxy resins, such as polyaryl ethers such as polyaryl sulfones and polyaryl ether sulfones, polyether ketones, polyphenylene ethers, and the like, as well as polyarylates, polyamides, polyamides, are known in the art. -Imide, polyether imide, polycarbonate, phenoxy resin and the like are known. The thermoplastic polymer selected is always soluble in the uncured epoxy resin composition when the purpose of including the thermoplastic polymer is to improve viscosity, processability and handling properties. The proportion of thermoplastic polymer used will depend in part on the thermoplastic polymer selected and the particular end use intended. However, for most purposes the composition is
Total amount of diamine curing agent and epoxy resin component 100 pbw
It contains 0 to 30 pbw of thermoplastic resin.

The epoxy composition may additionally contain accelerators to improve the cure rate. The accelerator is
It can be selected from among those widely known and used in the epoxy resin compounding industry and used in customary amounts. Promoters found to be effective for these purposes include BF ₃ : monoethylamine,
BF ₃ : triethanolamine, BF ₃ : piperidine and Lewis acids such as BF ₃ : 2-methylimidazole: amine complexes, imidazole, 1-methylimidazole, 2
Amines such as -methylimidazole, N, N-dimethylbenzylamine, etc., acid salts of tertiary amines such as p-toluenesulfonic acid: imidazole complexes, FC-520 (3
Salts of such trifluoromethanesulfonic acid obtained) from -M Company, organo phosphonium halide, dicyandiamide, 4,4 ^'- methylenebis (phenylene-methylurea) and 1,1 dimethyl-3-phenyl urea. It is also possible to use mixtures of such promoters. In some end uses it may be desirable to include dyes, pigments, stabilizers, thixotropic agents, etc., and these and other additives should be included as necessary at levels commonly practiced in the composite industry. You can Upon curing, the matrix resin composition forms a substantially single continuous hard phase except for any particulate additives, fillers and reinforcing agents that may be used.

Prior to curing, the matrix resin composition is combined with continuous fiber reinforcement or structural fibers and particulate modifiers used in the manufacture of reinforced composites in accordance with the practice of this invention. Suitable structural fibers can generally be characterized as having a tensile strength greater than 100 kpsi and a tensile modulus greater than 2 million psi. Fibers useful for these purposes include carbon or graphite fibers, glass fibers and fibers formed of silicon carbide, alumina, titania, boron and the like, and also polyolefins, poly (benzothiazole), poly (benzimidazole), etc.
, Polyarylate, poly (benzoxazole),
Included are fibers formed from organic polymers such as aromatic polyamides, polyaryl ethers, and the like, and also mixtures of two or more of such fibers. Preferably, the fibers are selected from glass fibers, carbon fibers and aromatic polyamide fibers such as those sold under the trade name "Kevlar" by the DuPont company. The fibers are typically in the form of continuous tows of 500 to 420,000 filaments and can be used as continuous unoriented tape or as a woven fabric.

The polyamide particles used in the practice of this invention consist of finely divided polyamide resin and have an essentially spherical sponge-like structure. The polyamide particles are generally 1 to 75 microns, preferably about 1 to about 2
It has an average diameter of 5 microns, more preferably about 2 to about 15 microns. The polyamide particles can be further characterized as porous, ie having a large internal pore volume, and the powder formed from such polyamide particles is usually greater than 5 m ² / g, preferably greater than about 9 m ² / g and 30 m. It has a large specific surface area of ² / g or more.
The specific surface area of such powder is measured according to a usual BET method. It will be appreciated that other physical forms of porous polyamide particles such as flakes, cylindrical polyamide particles or fibrid-like materials are also useful in the practice of the present invention, although such forms are not preferred. While pore volume can be considered a measure of the porosity of polyamide particles, polyamide particles useful in the practice of the present invention typically have large pore volumes, preferably greater than about 1.5 cm ³ / g. Pore volume as large as 0.5 cm ³ / g or more.

The porous polyamide particles useful in the practice of the present invention can be formed from any porous polyamide. The polyamide selected, in its final particle form, has sufficient heat resistance and hardness to resist being melted, compressed or flattened under the pressures and temperatures encountered during fabrication and curing of the laminate. And has rigidity. In addition, the polyamide is selected to be substantially insoluble in the matrix resin composition prior to gelation to preserve the unique surface properties of the particles.

Polyamide resins that can be used include polycaprolactam (nylon 6), polyhexamethylenediamine sebacamide (nylon 66), polyundecanoamide (nylon 11), polydodecanoamide.
Any of the readily available nylon resins such as (nylon 12) and the like. Producing particles having the required porosity from such resins has been described in the prior art, for example in US Pat. Nos. 4,831,061 and 2,359,
No. 877 and JP-A No. 62-240325, refer to them if necessary. Various porous polyamide particles and porous nylon coated particles suitable for use in the practice of the present invention are available, including porous nylon 6 particles, porous nylon 11 particles and porous nylon 12 particles. Is.

The particulate modifiers used to fabricate the composite include the porous polyamide particles of the present invention, including all of the various particulate modifiers known in the art for use in reinforcing composites. It may consist solely of, or may be a mixture of such particles with, for example, non-porous particles formed from cross-linked rubber or from hard resins such as polystyrene, polyphenylene ether, polysulfone and the like.

The reinforced composite structure of the present invention comprises individual layers formed by embedding continuous fibers in a matrix resin,
The layers are then separated or usually separated, and the layer surfaces form layer regions or spacing layers of matrix resin filled with porous polyamide particles. The particles serve to separate the layers and thus the thickness of the spacing layer is directly related to particle size.

As used herein, the term "particle size" refers to
It refers to the size of the particles that determines phase separation, and for small irregular or substantially spherical particles is the particle diameter. Since it is not practical in most cases to obtain particles that are uniform in overall size, the particulate modifier usually consists of a mixture of particles encompassing different particle sizes. The particle size is "Coulte
r "unter or" Multisizer "equipment or by any of the variations of standard methods such as by" Granulometer "equipment. Useful for strengthening composites in accordance with practice of the invention and Effective particle modifiers are those in which the majority of the particles have an average diameter in the range of 1 to about 75 microns. Suitable mixtures of powdered particulate materials for the purposes of the present invention include those of the sieve classification. It can be obtained by classifying the particle mixture using known methods such as.

The use of granular mixtures of varying particle size can have other deleterious effects and is therefore less preferred. Uniform distribution of a mixture of particles in a matrix resin can be made difficult by the presence of very large particles and thus the coating properties of the filling resin are not constant. The presence of a small number of very large (> 50 micron) particles widely dispersed in a film of uncured filled matrix resin attached to one or both sides of the prepreg tends to form significant peaks or high specks on its outer surface. The presence of such high specks affects the apparent surface roughness, thus reducing the surface tack of the prepreg by preventing complete and effective contact between layers in the deposition operation. The decrease in tackiness is particularly noticeable in the case of a particle mixture having a wide particle size distribution, and thus a narrowly distributed particle mixture is preferred.

The proportion of each component used to make the reinforced composites of this invention will depend in part on the intended end use and the particular resin, fiber and resin particles selected. Overall, the composite consists of about 20 to about 80% by weight of continuous fibers and the balance matrix resin and particles, and the particles are 1-based on the total weight of the particles and matrix resin composition. This corresponds to about 25% by weight. Although the level of resin particles required to strengthen the composite is within the above range, the optimum level will necessarily vary depending on the matrix resin type, fiber loading, particle type and similar factors. However, it must be determined accordingly for the particular fiber and resin system used. In general, it is desirable to use the lowest level of particles that will provide the desired improvement in composite toughness. Although more than optimum levels can be used, the resulting toughness enhancement is modest and other physical properties such as high temperature / wet strength can be detrimentally affected. Composites in which a very high fraction of particles are spaced in the interlayers appear to be most effective in providing toughness enhancement at the lowest levels of particles.

The methods commonly used for making laminated composites can be readily adapted to fabricate the composites of this invention. Generally, such composites are formed from impregnated tapes of uniformly arranged parallel fibers of continuous fibers or resin impregnated woven fabrics woven from continuous fiber tows. These impregnated fibrous structures, referred to as prepregs, can be of any convenient type, including melt coating, calendering, dip impregnation with resin solutions or molten resins, melt compression bonding of tapes or fabrics to films of matrix resin, etc. It can be prepared by impregnating a tape or woven fabric with a matrix resin composition in the uncured state using the method.

The composite is then formed by depositing a sheet or tape of prepreg to form a deposit and curing the deposit under pressure, usually with heat.
Each layer of prepreg (each containing continuous fibers and matrix resin in uncured form) adheres upon cure to a single structure (which is embedded in an essentially continuous and substantially uniform matrix resin phase). Have separate layers of continuous fibers)
Has an adjoining surface.

In forming the reinforced composite of the present invention, it is necessary to evenly distribute the porous polyamide particles between each of the prepreg layers. Various methods can be used for this purpose, and the placement of the particles on the surface of the prepreg can be carried out as a separate step before or during the deposition operation, or integrated into the tape or woven fabric impregnation step. It can also be converted. The former is called the two-step method, while the latter is called the one-step method.

The method for carrying out the two-step method is to physically distribute the particles on the surface of each prepreg tape or sheet during the deposition operation by spraying, spraying, diffusing or similar operations, and then distributing the particles in a liquid matrix resin. Coating the mixture on the surface of the prepreg with uniform dispersion in the composition, and forming a film of the particle-filled matrix resin composition and inserting the film between layers of the prepreg, such as by a deposition operation. The two-step method, which is based on a coating or intercalation process, provides additional matrix resin, thus ensuring that a suitable matrix resin is available to fill the layer area between the layers formed by the particles. Guarantee.

In another one-step method, the particles can be placed on the surface of the prepreg during the impregnation step by dispersing the particles in a matrix resin and then performing the impregnation step. In this method, a fibrous structure having a surface layer of filled resin is formed, for example, by placing a film of filled resin on the surface of a tape or woven fabric or by coating the filled resin directly on the surface. You can The continuous fibers are then embedded in the matrix resin by heating the fiber-resin structure with a melt crimp or ironing operation. The matrix resin is in a molten state and partly flows into the fibrous structure, thus a matrix filled with particles such that the tape or woven surface is too large to subsequently enter the interstices of the fibrous structure. The resin is left behind. This one-step method can be regarded as a filtration operation in which the fibrous structure acts as a filter medium through which the matrix resin is passed while retaining on the surface particles which are larger than the openings between the fibers.

As mentioned above, the deposition and curing steps used in the manufacture of reinforced composite structures other than the application method required for the incorporation of particles are conventional. These process steps can be carried out using any of the variations of conventional processing equipment, and conventional process steps, applications and variations as used normally in the composite industry are used. .

The invention will be better understood by considering the following examples, which are provided as an example of the invention. In the examples, all parts are by weight and all temperatures are given in ° C., unless stated otherwise.

[0036]

EXAMPLES In the examples the following materials and compositions were used: Epoxy -1: about 40 mol% of ^{N, N, N ', N} ' -
Tetraglycidyl bis (4-amino-3-ethylphenyl) methane, about 47 mol% (4-diglycidylamino-3-ethylphenyl)-(4-diglycidylaminophenyl) methane and about 12 mol% N, N, N ^{', N'} -
An epoxy resin mixture containing tetraglycidyl bis (4-aminophenyl) methane. Obtained from Ciba Geigy under the trade name "RD87-160". Tactix 556 : A mixture of polyglycidyl oligomers of polycyclic bridged hydroxy-substituted polyaromatic compounds. Dow·
It is obtained from the chemical company under the product name "Tactix 556". MY 9612: N, N, N ', N' - tetraglycidyl-4,4 ^'- methane diamine. Epoxy resin obtained from Ciba Geigy under the trade name "MY 9612". MY 0510 : O, N, N-triglycidyl-p-
Aminophenol. Product name "MY from Ciba Geigy"
Epoxy resin obtained as "0510". 3,3 ^{'-DDS: 3,3'} - diaminodiphenyl sulfone. Product name "HT-9719" from Ciba Geigy
As an aromatic diamine curing agent. 4,4 ^{'-DDS: 4,4'} - diaminodiphenyl sulfone. Product name "HT-9664" from Ciba Geigy
As an aromatic diamine curing agent. Omicure 94: as a curing accelerator obtained from Omicron Chemicals N, N-dimethyl -N ^'- phenyl urea. PEI : A polyetherimide thermoplastic resin obtained under the trade name "Ultem 1000" from General Electric Company. PES : Polyethersulfone obtained from ICI under the trade name "Vitrex 200". ERR4205 : Bis (2,3-epoxycyclophenyl) ether obtained from Union Carbide Corporation. SED-m: from Mallinckrodt Chemical Co. 4,4 ^'- bis (3-aminophenoxy) diphenyl sulfone. BAPP: 2, 2 from Mallinckrodt Chemical Company ^'- bis (4- (4'-aminophenoxy)
Phenyl) propane. BF ₃ TEA : Boron trifluoride-triethanolamine complex from Ingelhard Industries.

Particle Porous Nylon : 10 micron average particle size, 18.2
Porous nylon 12 particles with a BET surface area of m ² / g and a pore volume of 3.53 cm ³ / g. Non-Porous Nylon : 8 micron average particle size, 1.7 m ² / g
Porous Nylon 12 particles having a BET surface area of 1.10 and a pore volume of 1.10 cm ³ / g.

Fiber Carbon Fiber : Tradename "Thornel R40" grade carbon fiber from Amoco Performance Products Incorporated. This fiber is typically 12,000 per tow
0 filament number, 0.44g / m yield value, 810kp
si tensile strength, 42 mpsi tensile modulus and 1.81 g / cc
Has a density of. Each example uses a ribbon formed from fibers to
A prepreg having a fiber face weight of ˜150 g / m ² was prepared.

Test Procedure Particle size was measured by a granulometer and given as mean particle size, whereas BET surface area was measured by the krypton BET method and pore volume was measured by the mercury porosimetry method.

Post-Impact Compression Test (CAI) : This method, called Post-Impact Compression Test or CAI, is generally considered in the art as a standard test method. The test specimens are 6x4 in size panels cut from a 32 ply fiber reinforced composite sheet. Diameter 5 / in in Gardner Impact Tester
155 in the center of the 0.177 inch thick panel using the indenter
The panel is first impacted by applying an in-ib / in impact. The shocked panel is then attached to a jig and the longitudinal edges of the panel are raised and tested for residual compressive strength. For more information on the test, see "NAS
A Contractor Report 159293 "(NASA
1980, August).

The methods of the following examples are representative of those that can be used to prepare resin compositions, prepregs and composites useful in the practice of this invention. These methods are generally recognized by those skilled in the art as the methods commonly used to produce thermosetting resin compositions and composites.

Example 1 70.5 parts by weight (pbw) of MY9612 epoxy resin was heated to 110 ° C. in a flask with stirring and then 2
An epoxy resin composition was prepared by adding the 4,4 ^'-DDS diamine curing agent 9.5pbw and mixed at 110 ° C. 20 min. The mixture was cooled to 103 ° C. and 15 g of porous nylon particles were added under vigorous stirring. After stirring for a total of 20 minutes, the resin was drained from the reaction vessel and it was cooled. A second preparation of the composition was carried out, but omitting the particles. The prepreg was then prepared by dispersing the particulate modifier on one side in a two-step process substantially according to the method described herein. The prepreg had a fiber face weight of 149 g / m ² and a resin content of 38% by weight. Then, [+ 45/90 / -45 / 0]
12 in prepreg tape was deposited into a 15 x 15 in laminate using a ₄ s layer arrangement and then cured in an autoclave under 90 psi pressure at 355 ° C for 2 hours. The obtained composite panel was used as a test piece for CAI evaluation after cooling. The data are summarized in Table 1.

Comparative Example A An epoxy resin composition was prepared substantially by the method of Example 1, but substituting non-porous nylon particles as the modifier. For further evaluation, composites were prepared using the thermosetting epoxy composition substantially as described in Example 1. The composition and characterization data for this complex are summarized in Table 1.

Example 2 25.4 pbw of MY05 in 37.5 pbw of methylene chloride.
An epoxy resin composition was prepared by heating a solution of 10 epoxy and 37.3 pbw of MY9612 epoxy dissolved therein to 45 ° C. The mixture was stirred while adding 15 pbw polysulfone and the methylene chloride was distilled. The stirred mixture was further heated to remove methylene chloride, finally at 28 in vacuum and a temperature of 110 ° C. and held at this temperature for 1 hour. Then added 3,3 ^'-DDS of 21.5pbw for 5 minutes, then the mixture was removed 1 hour stirring to residual solvent at 100 ° C. under a reduced pressure of 28in. The temperature is lowered to 90 ℃ and 0.2 pbw of Omi
Cure 94 was added, stirring continued for 5 minutes and the resin allowed to drain. Prepregs and composites were prepared using the resin as a base resin and using porous nylon particles in a two-step process substantially according to the method described in Example 2. Resin and particles in a sigma blade mixer at about 50 ° C
And mixed at 50-75 ° C. for about 2 hours to ensure complete dispersion of the particles. The final prepreg tape is 14
It had a fiber face weight of 5 g / m ² and a resin content of 37.3% by weight. Composite specimens were prepared as in Example 1. The composition and characterization data of the complex are summarized in Table 1.

Control Example B The resin of Example 2 was combined with non-porous nylon particles according to substantially the same method and used to make composites for comparative testing. The final prepreg tape had a fiber face weight of 145 g / m ² and a final resin content of 37% by weight.

Example 3 42.0 pbw of ERR-4205 epoxy resin was placed in a resin kettle and heated to 130 ° C. with stirring before adding 8.0 pbw of PEI. Heating was continued for 30 minutes until a homogeneous solution was obtained, then 34.8 pbw SED-
m was added and the mixture was kept cooled to 105 ° C.
When the mixture became homogeneous again, 14.3 pbw BA
PP was added and heating was continued at 105 ° C for 10 minutes, then the mixture was cooled to 80 ° C, 0.9 pbw BF ₃ TEA was added, mixed for another 10 minutes and then discharged. 2,131
Place pbw of frozen resin in a sigma blade mixer, mix the resin for about 15 minutes until the temperature reaches 35 ° C, then 2
An interleaf composition was prepared from a portion of the resin by adding 91 pbw of porous nylon particles. The mixture reached a temperature of 45 ° C., during which mixing was continued for about 15 minutes to disperse the particles. Prepregs were prepared from filled and unfilled resin by a two-step method and then made into composite specimens substantially as described herein.

Comparative Example C An epoxy resin composition containing non-porous nylon particles was prepared substantially by the method of Example 3 and using the same base resin composition. Prepregs were prepared from filled and unfilled resin by a two-step method and then made into composite specimens substantially as described herein. Other examples of composites according to the invention were also prepared.

[0048] d of Example 4 800g of Tactix 556 epoxy resin and 800g
The mixture with poxy-1 epoxy resin was placed in a 5 liter resin flask and heated to 110 ° C. 165g
A solution of PEI thermoplastic resin in 3,000 g of methylene chloride in was added with stirring over 1.5 hours and then the solvent was removed. The mixture after removal of the residual solvent was degassed by heating for 45 minutes at 110 ° C. and vacuum, added 3,3 ^'-DDS of 590g and the diamine was dispersed and stirred for 25 minutes. The resin was then drained and it was cooled.

A sample of 86 pbw of resin was placed in a sigma blade mixer and allowed to warm to room temperature. 14 pbw
Porous nylon particles were added and the mixture was sheared for about 60 minutes to evenly disperse the particles, resulting in a resin temperature of about 70 ° C. A film of filled resin was formed as a coat weight of 33 g / m ² and a prepreg molding machine was used to produce a fiber content of 77% by weight and 145 g prepared from carbon fiber and unfilled resin substantially according to the procedure of Example 1. It was combined with a separately prepared prepreg tape having a fiber face weight of / m ² . The final prepreg tape had a fiber content of 37% by weight, a fiber face weight of 145 g / m ² and a nylon 12
The particles were dispersed in the resin coating on one side. 0.197
The composite was prepared essentially by the procedure of Example 1 to provide a test panel having a panel thickness of in. The characterization data for the complex is summarized in Table 1.

[0050]

[Table 1] Note: 1. See specification for particle composition and porosity. 2. CAI = compression after impact (1500 in-1b / in impact). See description for test procedure.

From the consideration of the CIA test data provided in Table 1, it will be apparent that the use of porous particles as the modifier substantially improves the damage tolerance of various epoxy compositions. Compare the CAI results of Examples 1-3 prepared using porous Nylon 12 particles with those of Controls A-C prepared using non-porous Nylon 12 particles. The improvement is generally about 5 kpsi, but this is considered by those skilled in the art to be a considerable and surprising increase in damage tolerance. Also consider the excellent CAI properties of the composite of Example 4.

It will thus be seen that the present invention is an improved fiber reinforced composite or composition comprising separate layers formed by embedding continuous structure fibers in a matrix resin, and the composites. It will also be appreciated that the toughening is achieved by including an essentially spherical sponge-like structure in the matrix resin component. The polyamide particles are generally 1 to 75 microns, preferably about 1 to about 25.
Microns more preferably have an average diameter of about 2 to about 15 microns and can be further characterized as having a large internal pore volume. Powders formed from such particles are usually greater than 5 m ² / g and preferably greater than about 9 m ² / g and 30 m ² measured according to the conventional BET method.
It has a large specific surface area of about / g or more. Further, the present invention is a method for strengthening a fiber-reinforced composite obtained by embedding continuous structure fibers in a thermosetting matrix resin in which a particulate modifier is dispersed, wherein porous particles as defined in the present specification are used. It will be appreciated that it also encompasses improved methods characterized in that they have been used.

Many more variations and modifications will be apparent to those skilled in the art, and these variations and modifications are intended to be included within the scope of the following claims.

Claims (9)

[Claims] 1. A fiber reinforced composition comprising continuous structure fibers and porous rigid polyamide particles in which a spherical sponge-like structure is embedded in a thermosetting matrix resin. 2. An (a) epoxy matrix resin composition,
(b) a laminated fiber-reinforced composite containing continuous structural fibers embedded in the matrix resin, the structural fibers comprising:
Comprising a plurality of individual layers forming a layer of spherical sponge-like structure and porous rigid polyamide particles having an average diameter in the range of about 1 to about 75 microns dispersed in the matrix resin. A laminated fiber reinforced composite consisting of. 3. A composite according to claim 1 or 2 in which the porous rigid polyamide particles represent 1 to about 25% by weight of the matrix resin. 4. The composite according to claim 1, wherein the epoxy matrix resin contains at least one epoxy resin, an aromatic diamine curing agent, and a thermoplastic resin as an optional component. 5. The epoxy matrix resin comprises at least one epoxy resin, an aromatic diamine curing agent, and from about 5 to about 30 pbw polyaryl ether and polyene based on the total weight of the epoxy resin and diamine curing agent components. The composite according to claim 4, which comprises a thermoplastic resin selected from the group consisting of ether imides. 6. The composite of any of claims 1-5, comprising about 20 to about 80% by weight structural fiber. 7. The composite according to claim 6, wherein the structural fibers are carbon fibers. 8. A spherical sponge-like structure and an average diameter of 1 to 25 microns are used to reinforce a laminated continuous fiber reinforced composite structure comprising a continuous carbon fiber reinforcement embedded in a cured epoxy resin composition. A method of using porous polyamide particles having. 9. The composite structure of claim 8, wherein the rigid polyamide particles represent from about 1% to about 25% by weight of the total weight of the epoxy resin composition and particles.