Elastic nonlinearity in metal-matrix composites

Parameters characterizing the elastic nonlinearity in metal-matrix composites are studied. The composites consist of the aluminum alloys 8091 or 7064 containing silicon carbide particles up to 20% volume fraction. Two different ultrasonic measurements, namely the acoustoelastic effect and the harmonic generation, are used for the determination of acoustic nonlinearity parameters. Their dependence on the content of SiC in the composite is investigated. The values of the nonlinearity parameter are found to decrease with increasing volume fraction of SiC-particles. The changes are explained in terms of the effects of SiC-particles on the second and third order elastic constants of the composites.