Toughening Mechanisms in Si-SiC Composites

Young 's modulus and fracture toughness of silicon-silicon carbide (Si-SiC) composites were determined at room temperature in a wide range of composition (0-90 vol % SiC) on commercial reaction-bonded (RB) Si-SiC as well as reaction sintered (RS) materials. The RS Si -SiC were prepared by high temperature reaction between silicon and carbon powders. At low SiC fractions (<60 vol% SiC )the RS composites show a crack-deflection toughening mechanism, while at higher SiC content they exhibit an abrupt change of fracture behavior resulting in higher surface energies than equivalent RB commercial Si-SiC.