Fracture Toughness in Rate-Dependent Solids Based on Viod Growth and Coalescence Mechanism

Abstract

Polymers and metals (and alloys) are widely used in many engineering applications. Crack growth and delamination are frequently observed failure models. The viscoelastic characteristic of polymeric materials can give rise to rate dependent crack growth; time dependent inelastic deformation of metals and alloys at high temperature can cause stable rate dependent crack growth along the grain boundary. This rate dependent crack growth usually initiates from the cavitations of voids. To describe the fracture process caused by void growth and coalescence in polymeric materials and metals (and alloys) at high temperature, the present thesis proposes a micromechanics model for void growth and coalescence in power law creeping solids incorporating the internal pressure. Steady-state fracture toughness is studied by a cell element approach in conjunction with the proposed micromechancis model. Detailed parametric studies of microstructural variables and the continuum property of the material on velocity dependent fracture toughness are performed. The simulations predict trends that agree with fracture toughness vs. crack velocity data reported in several experimental studies for polymers and steels.