Micromechanically based constitutive models for damage evolution in composite laminates

The structure of micromechanically based constitutive models for composite laminates developing transverse matrix cracks, local delaminations, fibre/m atrix debonding and fibre fractures is discussed. Nondimensional damage var iables describing these four damage modes are introduced and the principal form of a damage dependent constitutive law is formulated. As a special cas e transverse matrix cracking is investigated in further detail. A previousl y developed model for stiffness changes resulting from transverse matrix cr acking is presented, and criteria for initiation and growth of transverse c racks are discussed. In particular, limitations of the linear elastic fract ure mechanics approach are investigated and a cohesive zone model capturing crack bridging effects is suggested.