Introduction to damage mechanics

Abstract

This chapter introduces the main concepts used in Continuum Damage Mechanics (CDM), a specific theory for coupling constitutive equations with the material deterioration processes that evolve before fracture. Similarities and differences with classical Fracture Mechanics are pointed out.

The thermodynamic approach of CDM is briefly summarized, various concepts of effective stress are developed and their advantage and drawbacks underlined. Different ways are considered for coupling damage effects both with elasticity, rate independent plasticity and viscoplasticity. Specific applications are illustrated in ductile fracture, creep and fatigue of metallic materials.

Applications of CDM are shown for brittle materials and for composites, showing the modelling difficulties associated with the damage induced anisotropy and the damage deactivation effects under unloading and cycling conditions. The capability to describe the non linear behaviour induced by microcracking in quasi-brittle materials is illustrated by the case of ceramic matrix composites under uniaxial and multiaxial loading conditions.