Influence of Debonding Damage on a Crack Tip Field in Particulate-Reinforced Ductile-Matrix Composite

This paper deals with damage evolution around a crack tip in particulate-reinforced composite which contains hard particles dispersed homogeneously in a ductile matrix. In such a composite, debonding of particle-matrix interface is significant damage. The damaged particles have a weakening effect on overall mechanical properties of the composite; on the contrary, if the damage process could be controlled, the damage around a crack tip might be available as an energy dissipation mechanism in toughening. A new finite element method is developed based on Tohgo-Chou-Weng's constitutive relation which describes the elastic-plastic behavior and the damage behavior of particulate-reinforced composites. In this constitutive relation, it is assumed that the debonding damage is controlled by the stress of the particle and the statistical behavior of particle-matrix interfacial strength, that the debonded (damaged) particles are regarded as voids, and that a void volume fraction increases with deformation. Analyses of stress/strain field and damage evolution around a crack tip in particulate-reinforced composite are carried out by the FEM. With an increase in stress intensity, the debonding damage spreads out, and the damaged zone is constructed ahead of the crack tip. This debonding damage drastically influences the distributions of macroscopic and microscopic stress/strain fields around the crack tip. The initial particle volume fraction is higher, the damaged region ahead of the crack tip is narrower. This result suggests that the energy dissipation due to the debonding damage cannot be expected in the composite with high content of the particles.