Patent Publication Number: US-2019194404-A1

Title: Compositions and methods for making thermoplastic composite materials

Description:
CROSS REFERENCE 
     This application claims the benefit of priority of U.S. Provisional Patent Application No. 61/776,755 filed Mar. 11, 2013, which is hereby incorporated by reference. 
    
    
     FIELD 
     The present disclosure relates generally to composite materials. More particularly, the present disclosure relates to thermoplastic composite materials. 
     BACKGROUND 
     Composites are materials formed from a mixture of two or more components that produce a material with properties or characteristics that are different from those of the individual materials. Most composites comprise two parts, namely a matrix component and a reinforcement component. Matrix components are the materials that bind the composite together and they are often less stiff than the reinforcement components. Composite materials may be shaped under pressure at elevated temperatures. 
     The matrix components encapsulate the reinforcement components in place and distribute the load among the reinforcement components. Since reinforcement components are often stiffer than the matrix material, they are the primary load-carrying components within the composite. Reinforcement components may come in many different forms, such as: fibers, fabrics, particles, or rods. 
     Structures based on composite materials comprising a polymer matrix containing fibrous material have been developed. Such structures have been used in high performance composite manufacturing and may exhibit high strength, damage tolerance, interlaminar fracture toughness, flexibility, or any combination thereof. In highly demanding applications, such as, for example, structural parts in automotive and aerospace applications, composite materials are desired due to a combination of lightweight, high strength and temperature resistance. Manufacturing techniques have been developed for impregnating the fibrous material with a polymer matrix to change the properties of the composite structure. 
     There are many different types of composites, including plastic composites. Each plastic resin has its own unique properties, which when combined with different reinforcements create composites with different mechanical and physical properties. Plastic composites are classified within two primary categories: thermoset and thermoplastic composites. 
     In the case of thermoset composites, after application of heat and pressure, thermoset resins undergo a chemical change that cross-links the molecular structure of the material. Once cured, a thermoset part cannot be remolded. Thermoset plastics resist higher temperatures and provide greater dimensional stability than most thermoplastics because of the tightly cross-linked structure found in thermosets. 
     In the case of thermoplastic composites, the matrix components are not crosslinked and, therefore, are not as constrained as thermoset materials and can be recycled and reshaped to create a new part. 
     Thermoplastics that are reinforced with high-strength, high-modulus fibers to form thermoplastic composites provide dramatic increases in strength and stiffness, as well as toughness and dimensional stability. Thermoplastic composites can be melted by heating, reshaped and reformed if necessary, and then solidified by cooling. Thermoplastic materials can be either amorphous or semi-crystalline, each with its own set of properties. Common matrix components for thermoplastic composites include polypropylene (PP), polyethylene (PE), polyetheretherketone (PEEK) and nylon. 
     The structure and properties of the fiber-matrix interface play a major role in determining the mechanical and physical properties of a composite material. Stresses acting on the matrix are transmitted to the fiber across the interface, so the fiber and matrix need to interact to use the full properties of the fiber. The strength of this interaction can determine the properties of the composite itself. A weak interaction produces a tough composite since energy can be absorbed by various mechanisms, such as fiber pullout. A strong interaction between the fibers and matrix can produce a brittle composite. 
     It is, therefore, desirable to provide a composite material with desirable physical properties. 
     SUMMARY 
     The sulfone family of aromatic polymers includes thermoplastic materials with desirable mechanical properties. The backbone structure of polysulfone aromatic polymers includes sulfone linked aromatic units. This backbone chemical structure of these thermoplastic materials confers desirable physical and mechanical attributes to these polymers. These polymers may have, in comparison to polypropylene (PP), polyethylene (PE), polyetheretherketone (PEEK) or nylon thermoplastics: increased temperature resistance, strength, toughness, increased resistance to various chemicals, increased resistance to steam, or any combination thereof. 
     Previous attempts to create a composite from a polysulfone aromatic polymer matrix and reinforcing fibers include methods where the polymer is melted and the melted polymer is impregnated into the fibers, and methods where particles of polymer are used to impregnate the fibers. 
     Such methods have failed due to the lack of adhesion of the matrix to the fiber and poor control over the matrix/fiber distribution. Attempts to reduce the particle size of the polysulfone aromatic polymer in order to better impregnate the fibers have failed due to the toughness of the polymer preventing it from being micronized, even at cryogenic temperatures or using techniques such as jet milling. Furthermore, the high melt viscosity exhibited by many polysulfone aromatic polymers results in insufficient impregnation of the fiberous reinforcement component during the fiber impregnation phase of the composite manufacturing, during ply consolidation, or both. 
     The insufficient impregnation of the reinforcement component, in turn, may result in: (i) reduced adhesion between the reinforcement component and matrix, (ii) formation of voids in the matrix and associated undesirable physical properties of the composite; or (iii) both. 
     It is an object of the present disclosure to obviate or mitigate at least one disadvantage of previous composite materials. 
     In one aspect, the present disclosure provides a composite material that includes: a reinforcement component; a polysulfone aromatic polymer; and an adhesion promoter. 
     The polysulfone aromatic polymer may be: a polysulfone aromatic polymer, a polyethersulfone aromatic polymer, or a polyphenylsulfone aromatic polymer. 
     The polysulfone aromatic polymer may be a polymer that includes: 
     
       
         
         
             
             
         
       
     
     as monomeric units. 
     The polyethersulfone aromatic polymer may be a polymer that includes: 
     
       
         
         
             
             
         
       
     
     as monomeric units. 
     The polyphenylsulfone aromatic polymer may be a polymer that includes: 
     
       
         
         
             
             
         
       
     
     as monomeric units. 
     The adhesion promoter may be a polymer that includes: a polyamideimide polymer, a polyamide-amic polymer, a polymer comprising both polyamide-amic and amideimide as monomeric units, or a mixture thereof. 
     The adhesion promoter may include a polymer that includes both amide-amic and amideimide as monomeric units in a ratio of about 0.5:1 to about 1:1 amide-amic acid to amideimide. In particular examples, the ratio is between about 0.25:1 and about 0.95:1. In some examples, the ratio is about 0.5:1. 
     The adhesion promoter may be present in about 1 to about 25 weight % of the total weight of both the polysulfone aromatic polymer and adhesion promoter. The adhesion promoter may be present in about 5 to about 10 weight %. The adhesion promoter may be present in about 5 weight %. 
     The polysulfone aromatic polymer may have a tensile modulus of about 2.5 GPa, a tensile strength of about 80 MPa, or both. The polysulfone aromatic polymer may have a flexural modulus of about 2.4 GPa, a flexural strength of about 90 MPa, or both. 
     The reinforcement component may include: a carbon fiber, a glass fiber, an aramid fiber, a para-aramid fiber, a boron fiber, a basalt fiber, or any combination thereof 
     In another aspect, the present disclosure provides a process for forming a composite material. The process includes: impregnating a reinforcement component with a solvent-dissolved thermoplastic polysulfone aromatic polymer. The process may include removing at least a portion of the solvent from the impregnated reinforcement component, for example by evaporation. Using solvent-dissolved thermoplastic polymers to form composites has not been uniformly successful due to the difficulty of removing the solvents from the impregnated reinforcement components, and the difficulty in finding solvent/polymer combinations where the amorphous polymer is able to be dissolved in the solvent. 
     The impregnation may be achieved using a rotating drum, wet film application or by fiber dipping which involves pulling fibers through a solution trough of polymer matrix. The solvent-dissolved thermoplastic polysulfone aromatic polymer may be metered on the rotating drum using a doctor blade or a peristaltic pump. 
     The thermoplastic polysulfone aromatic polymer and solvent composition may include an adhesion promoter, such as a polyamideimide polymer, a polyamide-amic polymer, a polymer comprising both polyamide-amic and amideimide as monomeric units, or a mixture thereof. 
     The solvent-dissolved thermoplastic polysulfone aromatic polymer may be dissolved in any solvent that can solubilize the polymer and still be removed by evaporation. For example, the solvent may include a polar aprotic solvent. The polar aprotic solvent may be: N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl formamide (DMF), dimethylacetamide (DMAC), or any combination thereof. Alternatively, a chlorinated solvent, such as methylene chloride, can be used, though such solvents may be less desirable due to toxicity issues, environmental issues, or both. 
     The solvent-dissolved thermoplastic polysulfone aromatic polymer may be dissolved in a solvent mixture that also includes a second solvent compatible with the first solvent and the thermoplastic polysulfone aromatic polymer. The second solvent can be any solvent that forms a homogeneous blend with the first solvent and that does not cause the polymer to phase separate from the first solvent. The second solvent may be, for example, acetone, toluene, xylene, or any combination thereof. 
     The solvent-dissolved thermoplastic polysulfone aromatic polymer may be between 10 and 70% by weight of the polymer and solvent composition. For example, the solvent-dissolved thermoplastic polysulfone aromatic polymer may be between 25 and 50% by weight of the polymer and solvent composition, or may be between 30 and 40% by weight of the polymer and solvent composition. 
     The adhesion promoter, such as the polyamideimide polymer, may be dissolved in any solvent that can solubilize the polymer and still be removed by evaporation. For example, the solvent may include a polar aprotic solvent. The polar aprotic solvent may be, for example: N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl formamide (DMF), dimethylacetamide (DMAC), or any combination thereof. Alternatively, a chlorinated solvent, such as methylene chloride, can also be used, though such solvents may be less desirable due to toxicity issues, environmental issues, or both. 
     The adhesion promoter, such as the polyamideimide polymer, may be dissolved in a solvent mixture that also includes a second solvent compatible with the first solvent and the thermoplastic polysulfone aromatic polymer. The second solvent can be any solvent that forms a homogeneous blend with the first solvent and that does not cause the adhesion promoter or the polymer to phase separate from the first solvent. The second solvent may be, for example, acetone, toluene, xylene, or any combination thereof. 
     The solvent-dissolved thermoplastic polysulfone aromatic polymer and the solvent-dissolved adhesion promoter may be mixed to form a polysulfone-polyamideimide polymer blend dissolved in solvent. The polysulfone-polyamidimide polymer blend may be between 10 and 70% by weight of the polymer blend and solvent mixture. For example, polysulfone-polyamideimide polymeric blend may be between 25 and 50% by weight of the polymer blend and solvent mixture, or may be between 30 and 40% by weight of the polymer blend and solvent mixture. 
     The process may also include molding the composite material at a temperature between about 220° C. and about 420° C. The process may also include molding the composite material at a pressure between about 35 kPa to about 1500 kPa. 
     Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures. 
         FIG. 1  is an illustration of a composite material. 
         FIG. 2  illustrates two units of a polysulfone aromatic polymer. 
         FIG. 3  illustrates one unit of a polyethersulfone aromatic polymer. 
         FIG. 4  illustrates one unit of a polyphenylsulfone aromatic polymer. 
         FIG. 5  illustrates one unit of a polyamideimide polymer, which may be used as an adhesion promoter. 
         FIG. 6  illustrates one unit of a polyamide-amic polymer, which may be used as an adhesion promoter. 
         FIG. 7  is a schematic of an example of a fiber impregnation process according to the present disclosure. 
         FIG. 8  is a representation of ply layup. 
         FIG. 9  is a representation of a consolidated composite sheet with plural fiber angles. 
     
    
    
     DEFINITIONS 
     Throughout the present application, several terms are employed that are defined in the following paragraphs. These discussions of terms and phrases are intended to aid understanding of the present technology. 
     As used herein, the term “Composite Material” refers to a material system consisting of a mixture or combination of two or more micro- or macro-constituents that differ in form and chemical composition, and which are essentially insoluble in each other. In their most basic form, composite materials are a matrix (for example: polymer, ceramic, metal) with reinforcing agents (for example: fibers, whiskers, particulates). 
     As used herein, the terms “reinforcements” and “reinforcement component” refer to the principle load-bearing member of the composite material. Examples of reinforcement materials include carbon fiber (strong reinforcing fiber), boron fiber (superior to carbon fiber), aramid fiber (long chain polyamide with high tensile strength and light weight), para-aramid fiber (Kevlar® and Twaron®), basalt fiber (common extrusive volcanic rock used as alternative to metal reinforcements) and glass fiber (fiberglass) etc. 
     As used herein, the terms “matrix” and “matrix component” refer to the medium for binding and holding the reinforcements together, thereby forming a solid composite material, protecting the reinforcements from environmental degradation while providing finish, colour, texture, durability, or other functional properties. 
     As used herein, the term “polymer” refers to a molecule (macromolecule) composed of repeating structural units connected by covalent chemical bonds. 
     As used herein, the term “polymer matrix composite” refers to a polymer medium for binding and holding the reinforcements together, into a solid, protecting the reinforcement from environmental degradation while providing finish, colour, texture, durability and other functional properties. 
     As used herein, the terms “thermosetting polymer” and “thermoset polymer” refers to polymers that are heavily cross-linked to produce a strong three-dimensional network structure. These polymers are usually liquid or malleable prior to curing and are designed to be molded into a final form. Thermoset polymers have the property of undergoing a chemical reaction by the action of, for example, heat, a catalyst, or UV light to become an insoluble infusible substance. Once cross-linked, these thermosetting polymer will decompose, rather than melt, at sufficiently elevated temperatures. 
     As used herein, the term “thermoplastic polymer” refers to polymers that are linear or branched in which chains are substantially not interconnected to one another. Thermoplastic polymers are held together by non-covalent bonds, such as Hydrogen bonds and/or Van Der Waals forces. Heating thermoplastic polymers breaks these non-covalent bonds between polymer chains and the polymer can be molded into a new shape. These thermoplastic polymers become pliable or moldable above their glass temperature and return to solid state upon cooling. 
     As used herein, the term “tensile strength” is a measure of how much stress a polymer can endure before suffering permanent deformation. The tensile strength is the maximum amount of tensile stress that a material can withstand while being stretched or pulled before failing or breaking. 
     As used herein, the terms “tensile modulus” and “Young&#39;s Modulus” or “elastic modulus” is a measure of the elasticity of a polymer. The tensile modulus quantifies the elastic properties of linear objects which are either stretched or compressed and represents the ratio of the stress to the strain. 
     As used herein, the term “flexural modulus” is the ratio of stress to strain in flexural deformation, and is a measure of the tendency for a material to bend. 
     As used herein, the term “flexural strength” or “bend strength” or “fracture strength” is a measure of the ability of a material to resist deformation under load. 
     As used herein, the term “degradation temperature” means the temperature above which a polymer decomposes. 
     As used herein, the term “glass temperature” means the temperature range below which the amorphous polymer assumes a rigid glassy structure. 
     As used herein, the term “tows” refers to an untwisted bundle of continuous filaments. It may refer to man-made fibers, such as carbon fibers. 
     As used herein, the term “prepreg” refers to composite fibers where a matrix component, such as a polymer matrix of a resin, is impregnated in the fiber but the fiber has not been formed into its final composite structure. 
     DETAILED DESCRIPTION 
     Generally, the present disclosure provides a method for producing a thermoplastic composite material. The method includes impregnating a fiber with a solvent-dissolved thermoplastic polysulfone aromatic polymer. Preferably, the method includes incorporating an adhesion promoter to increase adhesion between the thermoplastic polysulfone aromatic polymer and the fiber as such an adhesion promoter may have a desirable effect on one or more physical properties of the resulting composite material. Particular examples of the method are discussed in greater detail below. 
     The present disclosure also provides a composite material that includes a polysulfone aromatic polymer combined with an adhesion promoter, and a reinforcing fiber. The polymer may have a tensile modulus of about 2.5 GPa, a tensile strength of about 80 MPa, or both. The reinforcing fiber may have a high modulus, high strength, and/or highly oriented continuous fibers. A tensile modulus of about 200 to about 700 GPa would be understood to be “high” for carbon fibers. A tensile modulus of about 70 to about 90 GPa would be understood to be “high” for glass fibers. A tensile strength of about 2 to about 7 GPa would be considered “high” for carbon fibers. A tensile strength of about 3.5 to about 4.5 GPa would be considered “high” for glass fibers. The adhesion promoter may be, for example, a polyamideimide or a polyamide-amic acid polymer. 
     The reinforcing fiber may be, for example: carbon fiber, glass fiber, aramid fiber, para-aramid fiber, boron fiber, basalt fiber, or any combination thereof. The thermoplastic polysulfone aromatic polymer composites may be used in the manufacture of components for, for example: the automotive industry, the aerospace industry, the telecommunications industry, the electronics industry, or the sporting goods industry. 
     The polysulfone aromatic polymer used to form a composite material according to the present disclosure may be, for example, a polysulfone aromatic polymer, a polyethersulfone aromatic polymer, or a polyphenylsulfone aromatic polymer. 
       FIG. 2  illustrates two units of an exemplary polysulfone aromatic polymer.  FIG. 3  illustrates one unit of an exemplary polyethersulfone aromatic polymer.  FIG. 4  illustrates one unit of an exemplary polyphenylsulfone aromatic polymer.  FIG. 5  illustrates one unit of an exemplary polyamideimide polymer, which may be used as an adhesion promoter.  FIG. 6  illustrates one unit of an exemplary polyamide-amic polymer, which may be used as an adhesion promoter. The adhesion promoter may be a mixture of adhesion promoters. 
     The adhesion promoter may be combined with the polysulfone aromatic polymer in an amount between about 1 and about 25% by weight of the total. In particular examples, the adhesion promoter is combined with the polysulfone aromatic polymer in an amount between about 5 and about 10% by weight. In specific examples, the adhesion promoter is combined with the polysulfone aromatic polymer in an amount about 5% by weight. 
     In particular examples, the adhesion promoter is a mixture of amideimide and polyamide-amic monomeric units. The polyamide-amic and amideimide monomeric units may be in a ratio of about 0.05:1 to about 1:1 of polyamide-amic acid to polyamideimide. In some examples, the ratio of amide-amic acid to amideimide in the adhesion promoter may be between about 0.25:1 and about 0.95:1. In particular examples, the ratio of amide-amic acid to amideimide ratio is about 0.5:1. 
     With regard to the method, the solvent used to dissolve the thermoplastic polysulfone aromatic polymer may be a single solvent or a mixture of solvents. In particular examples, the solvent is a polar aprotic solvent such as, for example: N-methyl pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl formamide (DMF), or dimethylacetamide (DMAC). In other examples, the solvent is a mixture of a polar aprotic solvent and another solvent that is compatible with both the aprotic solvent and the thermoplastic polysulfone aromatic polymer. The other solvent may be, for example: acetone, toluene, xylene, or any combination thereof. 
     Once dissolved in the solvent, the thermoplastic polysulfone aromatic polymer may be between 10 and 70% by weight of the polymer/solvent composition. In particular examples, the thermoplastic polysulfone aromatic polymer may be between 25 and 50%, or preferably between 30 and 40% by weight of the polymer/solvent composition. 
     The fiber may be impregnated with the mixture of polymer and solvent using an impregnation rotating drum to control the matrix/fiber distribution.  FIG. 7  is an illustration of an exemplary fiber impregnation process where the fibers are impregnated by the mixture of polymer and carrier using an impregnation rotating drum. In this exemplary process fiber tows ( 6 ) are first dried using an infrared heater ( 7 ) and then brought together side by side to form a fiber web ( 8 ). The polymer and solvent solution is then dispensed from a pressure pot ( 9 ) and metered by a doctor blade ( 10 ) to form a layer of controlled thickness on the impregnation rotating drum ( 11 ). The fiber web is brought in contact with the impregnation rotating drum ( 11 ), which is coated with the substantially uniform layer of the polymer solution and is then carried through a drying oven before being collected on a spool. 
     In the process illustrated in  FIG. 7 , the matrix-to-fiber volume ratio is controlled by the gap between the doctor blade ( 10 ) and the impregnation rotating drum ( 11 ). Additionally, the web width and the fiber spread are controlled by adjusting the tension on the fiber tows. The solvent may be partially or completely removed from the fiber-polymer solution mixture by evaporation, for example in drying ovens, to result in an impregnated unidirectional or multi-directional prepreg sheet or tape. 
     Such prepreg sheets of material may be stacked at varying angles with respect to the fiber direction to create preforms with desired mechanical properties, thickness and weight.  FIG. 8  illustrates a ply layup.  FIG. 9  illustrates a consolidated composite sheet with plural fiber angles. 
     The consolidation of the preforms may be completed, for example, by compression molding or stamping at temperatures between about 220° C. and about 420° C., pressures between about 35 kPa to about 1500 kPa, or both. 
     Thermoplastic composites as described herein may be used in a variety of applications such as, for example, components for: automobiles, trucks, commercial airplanes, aerospace, hand held devices (such as cell phones), recreation or sports equipment (such as hockey sticks, golf clubs, bicycle frames, athletic shoes and helmets), structural components for machines, or electronics (such as laptops, tablets, and televisions). 
     EXAMPLES 
     Example 1 
     Preparation of an Exemplary Polyarylsulfone Matrix Solution with Adhesion Promoter 
     2800 grams of N-Methyl-2-pyrrolidone (NMP) were poured into a 5 liter round bottom reactor equipped with overhead stirrer, addition funnel, thermocouple and condenser. The reactor was placed in a heating mantle and the temperature was raised to 60° C. while stirring. 1200 grams of Udel®-1700 Polysulphone (PSU) or Radel®-5800 Polyphenylsulfone (PPSU) from Solvay Plastics (exemplary polyarylsulfone polymers) was slowly added to the stirred NMP. After 3 hours, a 30% concentration by weight homogeneous (Solution A) was produced. 
     The Udel®-1700 Polysulphone (PSU) polymer has a tensile modulus of 2480 MPa, a tensile strength of 70.3 MPa, a flexural modulus of 2690 MPa, and a flexural strength of 106 MPa. It has a drying temperature of 135 to 163° C., a melting temperature of 329 to 385° C., and a mold temperature of 121 to 163° C. 
     The Radel®-5800 Polyphenylsulfone (PPSU) polymer has, at 3.18 mm, a tensile modulus of 2340 MPa, a tensile strength of 69.6 MPa, a flexural modulus of 2410 MPa, and a flexural strength of 91.0 MPa. It has a drying temperature of 149° C., an injection melting temperature of 360 to 391° C., and a mold temperature of 138 to 163° C. 
     2800 grams of NMP were poured into a 5 liter round bottom reactor equipped with overhead stirrer, addition funnel, thermocouple and condenser. The reactor was placed in a heating mantle and the temperature was raised to 60° C. while stirring. 1200 grams of Torlon® 4000T Polyamideimide (PAI) powder from Solvay Plastics (a polyamideimide powder) was slowly added to the stirred NMP. After 3 hours, a 30% concentration by weight homogeneous solution (Solution B) was produced. 
     Solution A (3800 grams) was poured into a 5 liter round bottom reactor equipped with overhead stirrer, addition funnel, thermocouple and condenser. The reactor was placed in a heating mantle and the temperature was raised to 60° C. while stirring. Solution B (200 grams) was then added to the stirred solution. After 15 minutes, a 30% concentration by weight homogeneous solution of PSU-PAI or PPSU-PAI blend was produced. The resulting polysulfone-polyamideimide blend was 5% by weight of the polyamideimide adhesion promoter. 
     Example 2 
     Preparation of an Exemplary Polysulfone-Polyamideimide Blend Carbon Fiber Composite Material 
     The composite prepreg was prepared by depositing a film of PPSU-PAI polymer solution (as prepared in Example 1) on the fiber tows, followed by drying the solvent in an oven. Specifically, the solution was dispensed from a reservoir and gravity-fed onto a rotating drum. The thickness of the polymer solution film was controlled by an adjustable doctor blade. The impregnated web was then pulled through an enclosed oven that was set at about 215° C. to evaporate the NMP solvent. The dried prepreg was collected with a take-up roller. The solvent vapor produced in the oven was forced through a solvent recovery cooling system. The out-going gas temperature of the solvent recovery system was 22° C. or less. The prepregs prepared had a nominal polymer content of about 40% by weight. The carbon fiber areal weight was about 66.7 g/m 2 . Epoxy-sized carbon fiber (Grafil 34-700, Grafil Inc) was used. 
     Example 3 
     Testing of an Exemplary Polysulfone-Polyamideimide Blend Carbon Fiber Composite Material 
     Three types of analytical testing were done on the polyphenylsulfone-polyamidimide blend carbon fiber composite material. The three tests were Interlaminar Strength Testing, Three Point Bending and Dynamic Mechanical Analysis (DMA). 
     Interlaminar strength testing is an International standard test for fiber-reinforced thermoplastic composites (ASTM 3846). This test covers the determination of the in-plane shear strength. In-plane shear strength, as determined by this test method, is measured by applying a compressive load to a notched specimen of uniform width. The specimen is loaded edgewise in a supporting jig. Failure of the specimen occurs in shear between two centrally located notches machined halfway through its thickness and spaced a fixed distance apart on opposing faces. 
     Three point bending is an International Standard test for fiber-reinforced thermoplastic composites (ISO 14125). The method determines the flexural properties of composites under three-point loading. The test specimen, supported as a beam, is deflected at a constant rate until the specimen fractures or until deformation reaches some pre-determined value. During this procedure, the force applied to the specimen and the deflection are measured. The method is used to investigate the flexural behavior of the test specimens and for determining flexural strength, flexural modulus and other aspects of flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded in three-point flexure. The test geometry is chosen to limit shear deformation and to avoid an interlaminar shear failure. 
     Table 1 shows testing results from three point bending testing (ISO 14125) and Interlaminar strength testing (ASTM 3846). All values in Table 1 given for Polysulfone-Polyamideimide polymer blend carbon fiber composite are an average of 7 specimens±standard deviation. The exemplary polysulfone-polyamideimide polymer blend carbon fiber composite was compared to a carbon composite that uses epoxy as the matrix component. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Polyphenylsulfone- 
                   
                   
               
               
                   
                 Polyamidimide 
                 Gurit 
               
               
                 Property 
                 Blend 
                 SparPreg* 
                 Method 
               
               
                   
               
             
            
               
                 Matrix 
                 Polyphenylsulfone- 
                 Epoxy 
                 — 
               
               
                   
                 Polyamideimide 
               
               
                   
                 Blend 
               
               
                 Fiber type 
                 Carbon 
                 Carbon 
                 — 
               
               
                 Fibre Modulus (GPa) 
                 250 
                 255 
                 — 
               
               
                 Fiber Volume Fraction 
                 0.52 
                 0.56 
                 — 
               
               
                 Flexural Strength (MPa) 
                 1336 ± 96 
                 1368 
                 ISO 14125 
               
               
                 Flexural Modulus (GPa) 
                 107 ± 6 
                 114 
                 ISO 14125 
               
               
                 Shear Strength (MPa) 
                  43 ± 6 
                 NA 
                 ASTM D 
               
               
                   
                   
                   
                 3846 
               
               
                   
               
               
                 *Supplier: Newport Adhesives and Composites Inc. 
               
            
           
         
       
     
     DMA is a technique used to study and characterize materials. It is most useful for studying the viscoelastic behavior of polymers. A sinusoidal strain is applied and the stress in the material is measured, allowing one to determine the elastic modulus (energy stored in the material) and the loss modulus (energy lost through heat). The temperature of the sample or the frequency of the stress is often varied, leading to variations in the moduli. This approach can be used to locate the glass transition temperature of the material, as well as to identify transitions corresponding to other molecular motions. 
     Samples measuring 4.9 mm in width, 2.0 mm in thickness and 60 mm in length were cut from consolidated unidirectional plates using a computer numerical control (cnc) mill. The fiber volume content of the samples was measured to be 52+/−1% The samples were secured in the grips of a torsional hybrid rheometer/dma (Discovery Hybrid Rheometer—TA instruments, New Castle, Del.). The samples were prepared so that all the fiber reinforcements were parallel to the length of the sample. The temperature was controlled to 30° C.+/−0.1° C. by an environmental thermal chamber. The sample was deformed in torsion at a frequency of 1 hz and strain of 0.01%. The elastic and loss moduli were recorded. The elastic shear modulus was measured to be G′=4.8 GPa and the loss shear modulus was measured to be G″=41 MPa. 
     In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the examples. However, it will be apparent to one skilled in the art that these specific details are not required. 
     The above-described examples are intended to be exemplary only. Alterations, modifications and variations can be effected to the particular examples by those of skill in the art without departing from the scope, which is defined solely by the claims appended hereto.