Micromechanical modeling of dynamic fracture in heterogeneous materials

Fracture is the principal mode of failure for a variety of materials under dynamic conditions. The mathematical complexity precludes analytical solution to be obtained. The difficulty is especially pronounced when material inhomogeneities and anisotropy need to be considered.; Recently, alumina/titanium diboride (Al₂O₃/TiB ₂) composites with a wide range of micro and nano phase sizes and phase morphologies have been developed in the School of Materials Science and Engineering at Georgia Tech. In order to understand failure mechanisms in this material system and the influence of phase morphologies and phase size on fracture resistance, a numerical framework is needed to explicitly account for arbitrary microstructures and fracture patterns.; Micromechanical modeling and simulation provide an important approach for analyzing the effects of material inhomogeneity and anisotropy over a range of microscopic length scales. A framework is proposed in this research for explicit modeling and simulation of microscopic damage/fracture/failure processes. The model and approach account for the real arbitrary microstructural morphologies. A cohesive finite element method (CFEM) based on cohesive surface theory is used. A fully dynamic kinetic framework and finite deformation kinematic formulation are used. Mesh independence of solution is studied and verified.; Idealized microstructures containing circular and elliptical particles and real microstructures with arbitrary morphologies are used to investigate the effects of phase morphologies, phase size and phase anisotropy on fracture of this ceramic composite system. Numerical results show that rnicrostructural variations give rise to a range of fracture resistance. Higher fracture resistance is obtained from microstructures with fine evenly distributed microstructural reinforcement entities.; The failure mode is found to be significantly influenced by the interfacial bonding strength between the phases. Two distinct failure modes are observed for strong and weak bonding.