Micromechanical Strength of Particle in Composite Ceramic with Partial Debonding Interphase

The four-phase model is used to predict the strength of particles in composite ceramic with partial debonding interphase. Firstly the external strain of three-phase cell is determined. Based on the disturbance strain tensor of three-phase cell, the micromechanical stress field of the particle is obtained. Then based on the generalized thermodynamic force of the particle in damage process, the damage equivalent stress of the particle in the three-phase cell can be calculated. As the damage equivalent stress is equal to the ultimate stress of the particle, the micromechanical strength of particles in composite ceramic with partial debonding interphase is obtained. Finally, For Al2O3-ZrO2 composite ceramic with partial debonding interphase, the variations of the micromechanical strength of particles for different orientation angle and different particle diameter are analyzed. The result shows that the micromechanical strength of particles is determined by the 50° orientation three phase cell, and has obvious size dependence. The micromechanical strength of particle will decrease when the particle diameter increase.

Damage Model and Failure Stress of Ceramic Particle Ni Base Alloy Composite

For Ceramic particle Ni base alloy composite, experiments and damage evolution finite element analysis shows that arc-microcracks happen only at the interfaces between the particles and matrix, and then extend to the matrix. Composite strength is coincident with matrix failure. First, the three-phases model is used to determine the external strains of two-phases element. Then micromechanical stress field in the matrix is obtained. Based on the generalized thermodynamic force in damage process, the damage equivalent stress can be computed. As the damage equivalent stress is equal to the ultimate stress of the matrix, the failure stress of matrix in composites is given.

A Continuous Damage Mechanics Model for Ductile Fracture

A model of isotropic ductile plastic damage based on a continuum damage variable, on the effective stress concept and on thermodynamics is derived. The damage is linear with equivalent strain and shows a large influence of triaxiality by means of a damage equivalent stress. Identification for several metals is made by means of elasticity modulus change induced by damage. A comparison with the McClintock and Rice-Tracey models and with some experiments is presented for the influence of triaxiality on the strain to rupture.