Composite Materials in Automotive Alloys

1. الجامعة المستنصرية كلية الهندسة قسم الهندسة الميكانيكية مواد هندسية مرحلة 3 COMPOSITE MATERIALSد. ناظم مجبل فالحمواد هندسية 1-3

2. MECH 473 ~ LECTURE 15: COMPOSITES -Al alloys for automotive connecting rods and pistons can be strengthened and hardened by the addition of SiC (silicon carbide) particles. -The SiC particles are introduced at a temperature at which the alloy is in the solid plus liquid state, ie., by “compocasting”. CAST METALPARTICULATE MMC’S

3. MECH 473 ~ LECTURE 15: COMPOSITES Compocasting of Al-SiC: -Partially solidified alloy is stirred to break up dendrites (fig. a) -Particles of SiC are added at this temperature (fig. b) -In a pressure die casting machine, the solid mixture becomes thixotropic to form a high density casting (fig. c) CAST METALPARTICULATE MMC’S

4. MECH 473 ~ LECTURE 15: COMPOSITES Microstructure of cast Al Alloy reinforced with particles of SiC magnified X125 CAST METALPARTICULATE MMC’S

5. MECH 473 ~ LECTURE 15: COMPOSITES For particulate composites, the rule of mixtures predicts the density of the composite as well as other properties (although other properties may vary depending on how the dispersed phase is arranged) Density, r, is given as a fraction, f, as: RULE OF MIXTURES Where the subscripts m and f refer to the matrix and fiber.

6. MECH 473 ~ LECTURE 15: COMPOSITES For fiber reinforced composites, the rule of mixtures predicts the density of the composite as well as electrical and thermal conductivity along the direction of the fibers if they are continuous and unidirectional. Density, r, is given as a fraction, f, as: RULE OF MIXTURES For thermal conductivity: For electrical conductivity: Thermal and electrical energy can be transferred through the composite at a rate that is proportional to the volume fraction, f of the conductive material