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lecture03 - 1.3 Classifications of Composite Materials A...

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Unformatted text preview: 1.3 Classifications of Composite Materials A. Source a Composite materials can be divided into natural composites and man- made composites. Many man—made composites have been produced based on knowledge learned from observing natural composites, i.e. biological materials. a. b. C. d. B. Natural Composites _ Woods consist of cellulose fibers and lignin matrix. Bones consist of collagen fibrils and ceramic matrix. Biocomposites —— They are made of biodegradable natural fibers and matrices. Man— made Composites —~ In ancient Egypt and China, straw and mud were put together to be building bricks. Engineering Composites— Many modern engineering composites are produced to replace conventional metals for weight reduction. Geometry of Reinforcement ~ Depending on the geometry of reinforcement, composite materials can be divided into the following categories: a. .0 d. e. Nanocomposites ~ They are based on reinforcements 1n nanoscopic scale i. synthesize dodecahedrane (12- -sided) from methane (l), ethane (2) or butane (3) to build a three— dimensional ball- shaped molecule ii. C50 fullerene (bucky ball, spherene, soccerene, or truncated icosahedron) can be obtained from laser ablation or are discharge. iii. polyhedrons: Examples are tetrahedron, trianglular prism, rectangular prism, hexagonal prism, octahedron, rhombic dodecahedron, pentagonal dodecahedron, tetrakaidecahedron and icosahedron. Euler’s rule governs the construction of the polyhedrons, i.e. F + V — E = 2, where F is face, V is vertex and E is edge. iv. CNT: Carbon nanotube have extraordinary mechanical properties, E = 1 TPa and 0‘]. =200GPa. Particulate Composites: Properties are hindered by high stress concentration. Fibrous Composites i. chopped/ short fibers: Short fibers have either random orientation or preferred orientation. ii. ontinuous fibers: Examples are unidirectional tapes consisting of straight fibers and swirling mats made of curl fibers. iii. two-dimensionally woven fabric composites: Plain weave is commonly used. iv. three-dimensionally braided composites Laminated Composites ~ Examples are bimetal, coating and cladding composites. Functionally Graded Materials ~ Known as FGM, materials of this category have gradual change of material density, microstructure and properties. C. Matrix Materials — There are cementitious composites, polymer matrix composites (PMC), metal matrix composites (MMC), ceramic matrix composites (CMC) and carbon/carbon composites (CCC). Website Resources S. Abrate, “World Wide Web Resources for Composite Materials,” Proceedings of the 17th technical conference, American Society for Composites, West Lafayette, IN, Oct. 21—23, 2002. ...
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