ENGINEERING MATERIALS

COMPOSITE MATERIALS

WHAT ARE COMPOSITE MATERIALS? SO FAR WE HAVE DISCUSSED MAIN CATEGORIES OF MATERIALS SUCH AS METALS AND THEIR ALLOYS, POLYMERS, AND CERAMICS. THESE THREE TYPES OF MATERIALS ARE IN FACT THE VIRGIN MATERIALS AND HAVE THEIR OWN IDENTITY WITH SPECIFIC TYPES OF PROPERTIES. FURTHERMORE, THESE ARE THE MAIN MATERIALS WHICH HAVE WIDER APPLICATIONS IN DIFFERENT AREAS OF SCIENCE & ENGINEERING. HOWERE, THERE ARE STILL MANY SITUATIONS IN ENGINEERING APPLICATIONS WHERE NO SINGLE MATERIAL WILL BE SUITABLE TO MEET PARTICULAR DESIGN REQUIREMENTS.

WHAT ARE COMPOSITE MATERIALS? IN SUCH SITUATIONS TWO MATERIALS IN COMBINATION MAY POSSESS THE DESIRED PROPERTIES AND PROVIDE A FEASIBLE SOLUTION TO THE MATERIALS-SELECTION PROBLEM. THE TERM COMPOSITE CAN REFER TO ANY MULTI-PHASE MATERIAL. HOWEVER, IT IS USUALLY RESTRICTED TO TAILOR MADE MATERIALS IN WHICH TWO OR MORE PHASES HAVE BEEN COMBINED TO YIELD PROPERTIES NOT PROVIDED BY THE CONSTITUENTS ALONE. THE CONTINOUS PHASE, THE PARENT PHASE, IN A COMPOSITE MATERIAL IS REFERRED TO AS THE MATRIX. OTHER PHASES WHICH PROVIDE REINFORCEMENTS ARE KNOWN AS DISPERSED PHASES.

TECHNICALLY, A COMPOSITE MATERIAL IS A MATERIALS SYSTEM COMPOSED OF A SUITABLY ARRANGED MIXTURE OF COMBINATION OF TWO OR MORE MICRO- OR MACROCONSTITUENTS WITH AN INTERFACE SEPARATING THEM THAT DIFFER IN FORM AND CHEMICAL COMPOSITION AND ARE ESSENTIALLY INSOLUBLE IN EACH OTHER. IN DESIGNING COMPOSITE MATERIALS, SCIENTISTS AND ENGINEERS HAVE INGENIOUSLY COMBINED VARIOUS METALS, POLYMERS, AND CERAMICS TO PRODUCE A NEW GENERATION OF EXTRAORDINARY MATERIALS. MOST OF THE COMPOSITE MATERIALS HAVE BEEN PRODUCED TO IMPROVE COMBINATIONS OF MECHANICAL CHARACTERISTICS SUCH AS STIFFNESS, TOUGHNESS, AND AMBIENT AND ELEVATED TEMPERATURE STRENGTH.

APPLICATIONS VERY SPECIFIC APPLICATIONS OF COMPOSITES ARE AS FOLLOW: STRAW IN CLAY CONSTRUCTION BY EGYPTIANS AEROSPACE INDUSTRY SPORTING GOODS AUTOMOTIVE CONSTRUCTION

TYPES OF COMPOSITE MATERIALS THERE ARE FIVE BASIC TYPES OF COMPOSITE MATERIALS: FIBRE, PARTICLE, FLAKE, LAMINAR OR LAYERED AND FILLED COMPOSITES.

TYPES OF COMPOSITES MMC’s CMC’s PMC’s FIBERGLASS METAL CERAMIC POLYMER MATRIX PHASE/REINFORCEMENT PHASE METAL CERAMIC POLYMER POWDER METALLURGY PARTS – COMBINING IMMISCIBLE METALS CERMETS (CERAMIC-METAL COMPOSITE) BRAKE PADS CERMETS, TIC, TICN CEMENTED CARBIDES – USED IN TOOLS FIBER-REINFORCED METALS SIC REINFORCED AL2O3 TOOL MATERIALS FIBERGLASS   KEVLAR FIBERS IN AN EPOXY MATRIX ELEMENTAL (CARBON, BORON, ETC.) FIBER REINFORCED METALS AUTO PARTS AEROSPACE RUBBER WITH CARBON (TIRES) BORON, CARBON REINFORCED PLASTICS MMC’s CMC’s PMC’s METAL MATRIX COMPOSITES CERAMIC MATRIX COMP’S. POLYMER MATRIX COMP’S

METAL MATRIX COMPOSITES THE TERM MMC COVERS A RANGE OF MATERIALS AND NOT MERELY COMPOSITES WITH CONTINUOUS FIRBE REINFORCEMENT. EARLY MATERIALS WERE TUNGSTEN FILAMENT WIRE STRENGTHENED WITH A DISPERSION OF THORIA AND SINTERED ALUMINUM POWDER (SAP). OTHER MATERILS STRENGTHENED IN SIMILAR MANNER AND DEVELOPED ARE THORIA DISPERSION NICKEL ALLOYS FOR HIGH TEMPERATURE SERVICE. SIMILARLY DEVELOPMENT OF EUTECTIC NICKEL-BASED SUPER ALLOYS. RECENTLY THERE HAVE BEEN MUCH INTEREST IN THE DEVELOPMENT OF MMCs WITH THE MAIN EMPHASIS FOR USING ALUMINIUM AND TITANIUM WITH EITHER CONTINUOUS FIBRE REINFOCEMENT OR DISCONTINUOUS PARTICLE REINFOCEMENT.

ALUMINIUM WITH PARTICULATE REINFORCEMENT BY ALUMINA OR SILICON CARBIDE CAN BE USED FOR THE MANUFACTURE OF CYLINDER LINERS, PISTONS AND PULLEYS. SOME MATRIX-REINFORCEMENT COMBINATIONS ARE HIGHLY REACTIVE AT ELEVATED TEMPERATURES, AND HENCE COMPOSITE DEGRADATION MAY BY BE CAUSED. THIS PROBLEM, HOWEVER, MAY BE RESOLVED BY APPLYING SOME TYPE OF SURFACE COATING. AUTOMOBILE COMPANIES HAVE RECENTLY STARTED TO USE MMCs IN PRODUCTS. THE TOYOTA COMPANY HAS USED ALUMINA FIRBRE REINFOCED ALUMINIUM IN ITS DIESEL ENGINES FOR SOME YEARS. HONDA COMPANY HAS PRODUCED A CAST ALUMINIUM CYCLINDER BLOCK WITH SELECTIVE REINFOCEMENT BY BOTH ALUMINA AND CARBON FIRBRES.

CERAMIC MATRIX COMPOSITES THE DEVELOPMENT OF CERAMIC MATRIX COMPOSITE MATERIALS WITH REINFOCING FIBRES OFFERS THE POSSIBILITY OF MATERIALS WHICH ARE MORE DAMGE TOLERANT. CERAMICS ARE BRITTLE AND HAVE LOW FRACTURE TOUGHNESS AND HENCE FRACTURE TOUGHNESSES OF CERAMICS HAVE BEEN IMPROVED SIGNIFICANTLY BY THE DEVELOPMENT OF NEW GENERATION OF CMCs. THE DEMAND FOR GREATER EFFICIENCY AND HIGHER OPERATING TEMPERATURES IN AERO GAS TURBINE ENGINES HAS PROVIDED THE STIMULUS FOR RESEARCH AND DEVELOPMENT OF CMCs AS THEY OFFER THE POTENTIAL FOR USE IN FUTURE GENERATIONS OF JET POWER UNITS.

CERAMIC MATRIX COMPOSITES CURRENT RESEARCH, HOWEVER, IS CONCENTRATING ON TWO TYPES OF CMCs NAMELY SILICON CARBIDE FIBRE REINFOCEMENT WITH SILICON CARBIDE AND GLASS-CERAMIC COMPOSITES REINFOCED WITH SILICON CARBIDE. THIS TYPE OF MATERIALS ARE STILL UNDER DEVELOPMENT BUT OFFER THE POTENTIAL OF BEING SUITABLE MATERIALS FOR USE IN AERO ENGINES IN FUTURE. CERAMIC MATRIX COMPOSITES WITH PARTICULATE REINFORCEMENT ARE ALSO UDER DEVELOPMENT. BOTH TITANIUM CARBONNITRIDE AND ZIRCONIA HAVE BEEN USED AS REINFORCING PARTICLES WITHIN ALUMINA FOR THE MAUFACTURE OF CUTTING TOOLS TIPS WITH HIGHER HARNESS.

CERMETS ARE THOSE SPECIAL CMCs WHICH CONTAIN BETWEEN 80 – 90% OF CERAMIC. THE EARLIEST CERMET, THE HARD METAL, DEVELOPED IN THE EARLY OF 20TH CENTURY, WAS CEMENTED WITH TUNGSTEN CARBIDE. OTHER CERMETS ARE OXIDE-BASED AND SILICON CARBIDE BASED COMPOSITES WITH NICKEL, COBALT AND STAINLESS STEELS. THESE MAY BE USED AS GAS TURBINE ENGINE MATERIALS

POLYMER MATRIX COMPOSITES PMCs ARE THE TYPE OF COMPOSITE MATERIALS WHICH CONSISTS OF A POLYMER RESIN AS THE MATRIX WITH FIBRES AS THE REINFOCEMENT MEDIUM. THE MOST WIDELY USED AND CHEAP POLYMER RESINS ARE THE POLYSTERS AND VINYL ESTERS. THESE RESINS ARE USED PRIMARILY FOR GLASS FIBRE REINFOCED COMPOSITES. PMCs ARE USED IN THE GREATEST DIVERSITY OF APPLICATIONS OF COMPOSITE MATERIALS BECAUSE OF THEIR ROOM-TEMPERATURE PROPERTIES, EASE OF FABRICATIONS, AND COST.

POLYMER MATRIX COMPOSITES FOLLOWING TYPES OF PMCs ARE WIDELY USED: GLASS FIBRE-REINFOCEMENT POLYMER (GFRP) COMPOSITES IT IS A SIMPLE COMPOSITE HAVING GLASS FIBRE CONTAINED WITHIN A POLYMER MATRIX CARBON FIBRE-REINFOCEMENT POLYMER (CFRP) COMPOSITES IT IS A SIMPLE COMPOSITE HAVING CARBON FIRBRE CONTAINED WITHIN A POLYMER MATRIX ARAMID FIBRE-REINFOCED POLYMER COMPOSITES ITSELF A CERAMIC MATERIAL CONTAINED WITHIN A POLYMER MATRIX BORON, SILICON CARBIDE AND ALUMINIUM OXIDE FIBRE REINFORCED COMPOSITES

GLASS FIBRE-REINFORCED COMPOSITE MATERIALS ARE USED IN AUTOMOTIVE AND MARINE BODIES, PLASTIC PIPES, STORAGE TANKS, AND INDUSTRIAL FLOORING. CARBON-REINFORCED COMPOSITE MATERIALS FIND THEIR APPLICATIONS IN SPORTS AND RECREATIONAL EQUIPMENT, FILAMENT-WOUND ROCKET MOTOR CASES, PRESSURE VESSELS, AND AIRCRAFT STRUCTURAL COMPONENTS. ARAMID-REINFOCED COMPOSITE MATERIALS BECAUSE OF THEIR EXECELLENT PROPERTIES ARE USED IN BALLISTIC PRODUCTS, SPORTING GOODS, TIRES, ROPES, MISSILES CASES AND IN AUTOMOTIVE BRAKE AND CLUTCH LININGS AND GASKETS AS A REPLACEMENT OF ASBESOTS MATERIAL.

OTHER (CARBON, SILICON CARBIDE ETC) REINFOCED COMPOSITES ARE USED FOR MILITARY AIRCRAFT COMPONENTS, HELICOPTER ROTOR BLADES, TENNIS RACKETS, CIRCUIT BOARDS AND ROCKET NOSE CONES.

FIBRE COMPOSITES 1-D GIVES MAXIMUM STRENGTH IN ONE DIRECTION. IN FIBRE COMPOSITES, THE FIBRES REINFORCE ALONG THE LINE OF THEIR LENGTH. REINFORCEMENT MAY BE MAINLY 1-D, 2-D OR 3-D. FIGURE SHOWS THE THREE BASİC TYPES OF FİBRE ORİENTATİON. 1-D GIVES MAXIMUM STRENGTH IN ONE DIRECTION. 2-D GIVES STRENGTH IN TWO DIRECTIONS. ISOTROPIC GIVES STRENGTH EQUALLY IN ALL DIRECTIONS.

COMPOSITE STRENGTH DEPENDS ON FOLLOWING FACTORS: INHERENT FIBRE STRENGTH, FIBRE LENGTH, NUMBER OF FLAWS FIBRE SHAPE THE BONDING OF THE FIBRE (EQUALLY STRESS DISTRIBUTION) VOIDS MOISTURE (COUPLING AGENTS)

PARTICLE COMPOSITES PARTICLES USUALLY REINFORCE A COMPOSITE EQUALLY IN ALL DIRECTIONS (CALLED ISOTROPIC). PLASTICS, CERMETS AND METALS ARE EXAMPLES OF PARTICLES. PARTICLES USED TO STRENGTHEN A MATRIX DO NOT DO SO IN THE SAME WAY AS FIBERS. FOR ONE THING, PARTICLES ARE NOT DIRECTIONAL LIKE FIBERS. SPREAD AT RANDOM THROUGH OUT A MATRIX, PARTICLES TEND TO REINFORCE IN ALL DIRECTIONS EQUALLY.

PARTICLE COMPOSITES CERMETS METAL–PLASTIC PARTICLE COMPOSITES (1) OXIDE–BASED CERMETS (E.G. COMBINATION OF AL2O3 WITH CR) (2) CARBIDE–BASED CERMETS (E.G. TUNGSTEN–CARBIDE, TITANIUM–CARBIDE) METAL–PLASTIC PARTICLE COMPOSITES (E.G. ALUMINUM, IRON & STEEL, COPPER PARTICLES) METAL–IN–METAL PARTICLE COMPOSITES AND DISPERSION HARDENED ALLOYS (E.G. CERAMIC–OXIDE PARTICLES)

FLAKE COMPOSITES ALUMINUM MICA GLASS FLAKES, BECAUSE OF THEIR SHAPE, USUALLY REINFORCE IN 2-D. TWO COMMON FLAKE MATERIALS ARE GLASS AND MICA. (ALSO ALUMINUM IS USED AS METAL FLAKES) A FLAKE COMPOSITE CONSISTS OF THIN, FLAT FLAKES HELD TOGETHER BY A BINDER OR PLACED IN A MATRIX. ALMOST ALL FLAKE COMPOSITE MATRIXES ARE PLASTIC RESINS. THE MOST IMPORTANT FLAKE MATERIALS ARE: ALUMINUM MICA GLASS

FLAKE COMPOSITES BASICALLY, FLAKES WILL PROVIDE: UNIFORM MECHANICAL PROPERTIES IN THE PLANE OF THE FLAKES HIGHER STRENGTH HIGHER FLEXURAL MODULUS HIGHER DIELECTRIC STRENGTH AND HEAT RESISTANCE BETTER RESISTANCE TO PENETRATION BY LIQUIDS AND VAPOR LOWER COST

LAMINAR COMPOSITES A LAMINA (LAMINAE) IS ANY ARRANGEMENT OF UNIDIRECTIONAL OR WOVEN FIBERS IN A MATRIX. USUALLY THIS ARRANGEMENT IS FLAT, ALTHOUGH IT MAY BE CURVED, AS IN A SHELL. A LAMINATE IS A STACK OF LAMINA ARRANGED WITH THEIR MAIN REINFORCEMENT IN AT LEAST TWO DIFFERENT DIRECTIONS.

LAMINAR COMPOSITES LAMINAR COMPOSITES INVOLVE TWO OR MORE LAYERS OF THE SAME OR DIFFERENT MATERIALS. THE LAYERS CAN BE ARRANGED IN DIFFERENT DIRECTIONS TO GIVE STRENGTH WHERE NEEDED. SPEEDBOAT HULLS ARE AMONG THE VERY MANY PRODUCTS OF THIS KIND. LIKE ALL COMPOSITES LAMINAR COMPOSITES AIM AT COMBINING CONSTITUENTS TO PRODUCE PROPERTIES THAT NEITHER CONSTITUENT ALONE WOULD HAVE. IN LAMINAR COMPOSITES OUTER METAL IS NOT CALLED A MATRIX BUT A FACE. THE INNER METAL, EVEN IF STRONGER, IS NOT CALLED A REINFORCEMENT. IT IS CALLED A BASE.

LAMINAR COMPOSITES UNREINFORCED–LAYER COMPOSITES (1) ALL–METAL LAMINAR COMPOSITES CAN BE DIVIDED INTO THREE BASIC TYPES: UNREINFORCED–LAYER COMPOSITES (1) ALL–METAL (A) PLATED AND COATED METALS (ELECTROGALVANIZED STEEL – STEEL PLATED WITH ZINC) (B) CLAD METALS (ALUMINUM–CLAD, COPPER– CLAD) (C) MULTILAYER METAL LAMINATES (TUNGSTEN, BERYLLIUM) (2) METAL–NONMETAL (METAL WITH PLASTIC, RUBBER, ETC.)

LAMINAR COMPOSITES REINFORCED–LAYER COMPOSITES (LAMINAE AND LAMINATES) (3) NONMETAL (GLASS–PLASTIC LAMINATES, ETC.) REINFORCED–LAYER COMPOSITES (LAMINAE AND LAMINATES) COMBINED COMPOSITES (REINFORCED–PLASTIC LAMINATES WELL BE BONDED WITH STEEL, ALUMINUM, COPPER, RUBBER, GOLD, ETC.)

FILLED COMPOSITES THERE ARE TWO TYPES OF FILLED COMPOSITES. IN ONE, FILLER MATERIALS ARE ADDED TO A NORMAL COMPOSITE RESULT IN STRENGTHENING THE COMPOSITE AND REDUCING WEIGHT. THE SECOND TYPE OF FILLED COMPOSITE CONSISTS OF A SKELETON 3-D MATRIX HOLDING A SECOND MATERIAL. THE MOST WIDELY USED COMPOSITES OF THIS KIND ARE SANDWICH STRUCTURES AND HONEYCOMBS.

COMBINED COMPOSITES IT IS POSSIBLE TO COMBINE SEVERAL DIFFERENT MATERIALS INTO A SINGLE COMPOSITE. IT IS ALSO POSSIBLE TO COMBINE SEVERAL DIFFERENT COMPOSITES INTO A SINGLE PRODUCT. A GOOD EXAMPLE IS A MODERN SKI. (COMBINATION OF WOOD AS NATURAL FIBER, AND LAYERS AS LAMINAR COMPOSITES)

FIBRE REINFORCEMENTS THE TYPICAL COMPOSITE CONSISTS OF A MATRIX HOLDING REINFORCING MATERIALS. THE REINFORCING MATERIALS, THE MOST IMPORTANT IS THE FIBRES. A FIBRE IS A THREAD-LIKE FORM WITH LENGTH-TO-DIAMETER RATIOS OF THE ORDER OF 10³ OR GREATER. THE TERM EMBRACES THIN METAL WIRES AS WELL AS NATURAL AND SYNTHETIC FIRBRES SUCH AS WOOD, COTTON, POLYACRYLONITRILE AND NYLON. STRONG, STIFF FIBRE ARF PRODUCED FROM COLD-DRAWN METALS, CERAMICS, AND POLYMERS. THEY MAY BE INCORPORATED IN POLYMER, METAL OR CERAMICS MATRICES TO FORM FIBRE-REINFORCED COMPOSITES.

FIBRE REINFORCEMENTS STRONG, STIFF FIBRE ARF PRODUCED FROM COLD-DRAWN METALS, CERAMICS, AND POLYMERS. THEY MAY BE INCORPORATED IN POLYMER, METAL OR CERAMICS MATRICES TO FORM FIBRE-REINFORCED COMPOSITES. THEY SUPPLY THE BASIC STRENGTH OF THE COMPOSITE. HOWEVER, REINFORCING MATERIALS CAN CONTRIBUTE MUCH MORE THAN STRENGTH. THEY CAN CONDUCT HEAT OR RESIST CHEMICAL CORROSION. THEY CAN RESIST OR CONDUCT ELECTRICITY. THEY MAY BE CHOSEN FOR THEIR STIFFNESS (MODULUS OF ELASTICITY) OR FOR MANY OTHER PROPERTIES.

TYPES OF FIBRES THE FIBRES ARE DIVIDED INTO TWO MAIN GROUPS: GLASS FIBRES: THERE ARE MANY DIFFERENT KINDS OF GLASS, RANGING FROM ORDINARY BOTTLE GLASS TO HIGH PURITY QUARTZ GLASS. ALL OF THESE GLASSES CAN BE MADE INTO FIBERS. EACH OFFERS ITS OWN SET OF PROPERTIES. ADVANCED FIBRES: THESE MATERIALS OFFER HIGH STRENGTH AND HIGH STIFFNESS AT LOW WEIGHT. BORON, SILICON, CARBIDE AND GRAPHITE FIBERS ARE IN THIS CATEGORY. SO ARE THE ARAMIDS, A GROUP OF PLASTIC FIBERS OF THE POLYAMIDE (NYLON) FAMILY.

FIBRE GLASS FIBERGLASS PROPERTIES VARY SOMEWHAT ACCORDING TO THE TYPE OF GLASS USED. HOWEVER, GLASS IN GENERAL HAS SEVERAL WELL–KNOWN PROPERTIES THAT CONTRIBUTE TO ITS GREAT USEFULNESS AS A REINFORCING AGENT: TENSILE STRENGTH CHEMICAL RESISTANCE MOISTURE RESISTANCE THERMAL PROPERTIES ELECTRICAL PROPERTIES THERE ARE FOUR MAIN TYPES OF GLASS USED IN FIBERGLASS: A–GLASS C–GLASS E–GLASS S–GLASS

FIBRES – ARAMID, CARBON ARAMID ARE HIGH PERFORMANCE REPLACEMENT FOR GLASS FIBER. THESE ARE USED FOR ARMOR, PROTECTIVE CLOTHING, INDUSTRIAL, SPORTING GOODS. THIS MATERIAL HAS HIGHER STRENGTH AND ARE LIGHTER THAN GLASS AND ARE MORE DUCTILE THAN CARBON. CARBON IS THE 2ND MOST WIDELY USED FIBER. EXAMPLES OF ITS USE ARE AEROSPACE, SPORTING GOODS. ADVANTAGES OF CARBON ARE HIGH STIFFNESS AND STRENGTH, LOW DENSITY, INTERMEDIATE COST

OTHER FIBRE REINFORCEMENTS BORON HIGH STIFFNESS, VERY HIGH COST LARGE DIAMETER - 200 MICRONS GOOD COMPRESSIVE STRENGTH POLYETHYLENE - TRADE NAME: SPECTRA FIBER TEXTILE INDUSTRY HIGH STRENGTH EXTREMELY LIGHT WEIGHT LOW RANGE OF TEMPERATURE USAGE

OTHER FIBRE REINFORCEMENTS CERAMIC FIBERS VERY HIGH TEMPERATURE APPLICATIONS (E.G. ENGINE COMPONENTS) SILICON CARBIDE FIBER CERAMIC MATRIX SO TEMPERATURE RESISTANCE IS NOT COMPROMISED INFREQUENT USE

COATING AND HEAT TREATMENT OF MATERIALS QUESTIONS AND QUERIES IF ANY! IF NOT THEN GOOD BYE NEXT LECTURE COATING AND HEAT TREATMENT OF MATERIALS

ASSIGNMENT N0. 06 Q. NO. 01 – WHAT ARE POLYMERIC MATERIALS? DEFINE BRIEFLY DIFFERENT TYPES OF POLYMERS ALONG WITH THEIR SPECIFIC APPLICATIONS. Q. NO. 02 – DEFINE CERAMICS AND OUTLINE THEIR DIFFERENT TYPES. ALSO SPECIFY THEIR APPLICATIONS. Q. NO. 03 – WHAT ARE MMC, CMC & PMC? DEFINE AND EXPLAIN DIFFERENT TYPES OF COMPOSITE MATERIALS ALONG WITH THEIR APPLICATIONS.