Damping and Stiffness of Particulate Sic–Insn Composite

Metal matrix composites of silicon carbide particles in indium–tin alloy were fabricated with the aim of achieving a high value of the product of stiffness and viscoelastic damping tan, without excess density. Stiffness and viscoelastic damping were measured over a wide range of frequency. For monodisperse 40% by volume SiC, and for hierarchical 60% by volume SiC the composite damping increased compared with the matrix at frequencies above 100 Hz. Composite shear modulus was almost a factor two greater than matrix for 40% and a factor of four greater than that of matrix for 60%. The product of stiffness and damping exceedsthat of well-known materials including polymer damping layers. Hashin–Shtrikman analysis modelled the observed stiffness increase. The damping increase at higher frequency cannot be accounted for by a purely mechanical composite model; it is attributed to thermoelastic coupling and an increase in matrix dislocations during fabrication.