The energy approach recently proposed by Qiu and Weng (1992) is introduced to estimate the equivalent stress of the ductile matrix in Tohgo and Chou’s (1991) incremental damage theory for particulate-reinforced composites containing hard particles. In such a composite debonding of the particle-matrix interface is a significant damage process, as the damaged particles have a weakening effect while the intact particles have a reinforcing effect. In Tohgo-Chou’s theory, which describes the elastic-plastic behavior and the damage behavior of particulate-reinforced composites, it was assumed that the debonding damage is controlled by the stress of the particle and the statistical behavior of the particle-matrix interfacial strength, and that the debonded (damaged) particles are regarded as voids, resulting in an increased void concentration with deformation. On the other hand, Qiu-Weng’s energy approach provides a reasonable equivalent stress of the matrix in the porous material and particulate-reinforced composite even under a high triaxiality. The incremental damage theory developed here enables one to calculate the overall stress-strain response and damage evolution of the composite under high triaxial tension. The stress-strain relations for porous material obtained by the present incremental theory are completely consistent with that obtained by Qiu and Weng. The influence of the debonding damage on the stress-strain response is demonstrated for particulate-reinforced composites.

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