A MICROCRACK DAMAGE MODEL FOR BRITTLE MATERIALS

A damage model for brittle materials subject to arbitrary stress is developed. By considering dilute distributions of flat microcracks, self-similarly propagating in a linear elastic matrix, constitutive equations are obtained taking into account both stress- and damage-induced anisotropy. The crack size and, for closed cracks, the frictional sliding vector are assumed as internal variables; the evolution equations, obtained through properly defined sliding and crack growth criteria, make it possible to state the limit conditions of the stable response to applied stresses. Comparisons between experimental and theoretical results related to different loading paths show the capabilities of the model. Finally the unstable response to uniaxial stresses is analysed in order to show the influence of the stressing mode and of the crack distribution on the post-peak behavior.