A MICROMECHANICS-BASED DAMAGE MODEL FOR MICROCRACK-WEAKENED BRITTLE SOLIDS

In the present paper, a micromechanics-based, three-dimensional damage model for microcrack-weakened brittle solids is developed. In order t o describe the evolutionary damage state and anisotropic properties of materials, the concept of domain of microcrack growth (DMG) is define d as the union of all possible orientations of propagated microcracks after a loading path. Based on modified mixed-mode growth criteria of microcrack, the evolution of DMG as well as the overall effective comp liance tenser of damaged materials are formulated. Through a micromech anical analysis, the damage mechanisms and the complex constitutive be havior of materials are studied under complex loadings. The self-simil ar growth of open microcracks under tension, the mode-II growth and th e kinking of closed microcracks under compression and the influences o f these mechanisms on the mechanical properties of materials are all c onsidered. It is explained that axial splitting may occur in a materia l only when the lateral normal stresses have positive or a small negat ive value. And the condition for axial splitting of a material is give n. The evolutionary damage model is illustrated by two examples of uni axial tension and uniaxial compression and the theoretical results are compared with experimental data and theoretical results obtained by o thers.