Presentation of composite
- 4. ADVANTAGES OF COMPOSITES • Lower density • Non-corrosive • Non-conductive • Flexible, will not dent • Low maintenance • Long life • Design flexibility • Easy to Machine • Low cost
- 5. DISADVANTAGES OF COMPOSITES • Not often environmentally friendly • Low recyclability • Can be damaged • Low reusability • Anisotropic Properties
- 6. APPLICATION OF COMPOSITES • Aircraft • Boats and marine • Sporting equipment (Golf shafts, tennis rackets, surfboards, hokey sticks, etc.) • Automotive components • Wind turbine blades • Body armor • Building materials • Water pipes • Bridges • Tool handles • Ladder rails
- 7. COMPOSITE MATERIALS AND MANUFACTURING (VIDEO)
- 8. Composite Material Matrix Reinforcement Matrix Reinforcement Polymer Fiber Metallic Partical Ceramics Flake
- 10. CLASSIFICATION OF COMPOSITE MATERIALS BY MATRIX Polymer Matrix Composites (PMC) Metal Matrix Composites (MMC) Ceramic Matrix Composites (CMC)
- 12. CONT…
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- 14. ADVANTAGES OF MMC’S • Metal matrix composites are mainly used to provide advantages over monolithic metals such as steel and aluminum. • These advantages include higher specific strength and modulus by reinforcing low- density metals, such as aluminum and titanium. • lower coefficients of thermal expansion by reinforcing with fibers with low coefficients of thermal expansion, such as graphite; and maintaining properties such as strength at high temperatures.
- 15. ADVANTAGES OF MMC’S (CONT…) • Advantages over polymer matrix composites. These include higher elastic properties; higher service temperature; insensitivity to moisture; higher electric and thermal conductivities; and better wear, fatigue, and flaw resistances. • The drawbacks of MMCs over PMCs include higher processing temperatures and higher densities.
- 17. FABRICATION METHOD OF MMC • Fabrication methods for MMCs are varied. One method of manufacturing them is diffusion bonding (Figure 1.28), which is used in manufacturing boron/aluminum composite parts. A fiber mat of boron is placed between two thin aluminum foils about 0.05 mm thick. A polymer binder or an acrylic adhesive holds the fibers together in the mat. Layers of these metal foils are stacked at angles as required by the design. The laminate is first heated in a vacuum bag to remove the binder. The laminate is then hot pressed with a temperature of about 500°C and pressure of about 35 MPa in a die to form the required machine element.
- 19. APPLICATIONS OF MMC’S • Space: The space shuttle uses boron/aluminum tubes to support its fuselage frame. In addition to decreasing the mass of the space shuttle by more than 145 kg, boron/aluminum also reduced the thermal insulation requirements because of its low thermal conductivity. The mast of the Hubble Telescope uses carbon-reinforced aluminum.
- 20. CONT… • Military: Precision components of missile guidance systems demand dimensional stability — that is, the geometries of the components cannot change during use. Metal matrix composites such as SiC/aluminum composites satisfy this requirement because they have high microyield strength. In addition, the volume fraction of SiC can be varied to have a coefficient of thermal expansion compatible with other parts of the system assembly.
- 21. CONT… • Transportation: Metal matrix composites are finding use now in automotive engines that are lighter than their metal counterparts. Also, because of their high strength and low weight, metal matrix composites are the material of choice for gas turbine engines.
- 22. 3. CERAMIC MATRIX COMPOSITES (CMC) • Ceramic matrix composites (CMCs) have a ceramic matrix such as alumina calcium alumino silicate reinforced by fibers such as carbon or silicon carbide. • For use in high temperature and severe stress application Example: Automobile & aircraft gas turbine emgine.
- 23. ADVANTAGES OF CMC’S • High strength • Hardness • High service temperature limits for ceramics • Chemical inertness • Low density. However, ceramics by themselves have low fracture toughness. Under tensile or impact loading, they fail catastrophically.
- 24. CONT.. • Reinforcing ceramics with fibers, such as silicon carbide or carbon, increases their fracture toughness because it causes gradual failure of the composite. This combination of a fiber and ceramic matrix makes CMCs more attractive for applications in which high mechanical properties and extreme service temperatures are desired.
- 26. MANUFACTURING METHOD OF CMC • One of the most common methods to manufacture ceramic matrix composites is called the hot pressing method. • Glass fibers in continuous tow are passed through slurry consisting of powdered matrix material, solvent such as alcohol, and an organic binder (Figure). • The tow is then wound on a drum and dried to form prepreg tapes. The prepreg tapes can now be stacked to make a required laminate. Heating at about 500°C burns out the binder. • Hot pressing at high temperatures in excess of 1000°C and pressures of 7 to 14 MPa follows this.
- 30. CARBON - CARBON COMPOSITES • Carbon–carbon composites use carbon fibers in a carbon matrix. These composites are used in very high-temperature environments of up to 3315°C, and are 20 times stronger and 30% lighter than graphite fibers.
- 31. ADVANTAGES OF C-C COMPOSITES • Carbon is brittle and flaw sensitive like ceramics. Reinforcement of a carbon matrix allows the composite to fail gradually and also gives advantages such as ability to withstand high temperatures, low creep at high temperatures, low density, good tensile and compressive strengths, high fatigue resistance, high thermal conductivity, and high coefficient of friction.
- 32. MECHANICAL PROPERTIES OF C-C COMPOSITES
- 33. PROCESSING A C–C COMPOSITE Low-pressure carbonization A graphite cloth is taken, impregnated by resin (such as phenolic, pitch, and furfuryl ester), and laid up in layers. It is laid in a mold, cured, and trimmed. The part is then pyrolized, converting the phenolic resin to graphite.
- 34. The composite is then impregnated by furfuryl alcohol. The process drives off the resin and any volatiles. The process is repeated three or four times until the level of porosity is reduced to an acceptable level. Each time, this process increases its modulus and strength. Because carbon–carbon composites oxidize at temperatures as low as 450°C, an outer layer of silicon carbide may be deposited.
- 36. APPLICATIONS OF C-C COMPOSITES • Space shuttle nose cones: As the shuttle enters Earth’s atmosphere, temperatures as high as 1700°C are experienced. • Aircraft brakes: The carbon–carbon brakes cost $970/kg, which is several times more than their metallic counterpart; however, the high durability (two to four times that of steel), high specific heat (2.5 times that of steel), low braking distances and braking times (three-quarters that of berylium), and large weight savings of up to 450 kg on a commercial aircraft such as Airbus A300-B2K and A300-B4 are attractive.
- 37. CONT….. • Mechanical fasteners: Fasteners needed for high temperature applications are made of carbon–carbon composites because they lose little strength at high temperatures.