The Micromechanics of Deformation and Failure in Metal-Matrix Composites.

Metals reinforced with ceramic fibers or particulates are promising materials for use in new generations of aerospace structures, propulsion devices and energy conversion systems. Furthermore, the controllability of many of these variables opens up the possibility of engineering materials for specific applications, if the effects of alterations in microstructure can be predicted. However, metal-matrix composites often have low ductility and low fracture toughness. An improved understanding of the basic deformation and failure mechanisms is needed to overcome these problems. To this end, research was carried out in three areas 1 continuum modeling of deformation and fracture in metal-matrix composites, including the interaction between failure mechanisms using phenomenological constitutive relations to characterize each of the main failure modes in metal-matrix composites, reinforcement cracking, interfacial debonding and matrix void nucleation, growth and coalescence 2 numerical studies of the propagation of fast cracks along and across interfaces, with a particular focus on understanding crack propagation from a brittle phase into a ductile phase and 3 discrete dislocation modeling of matrix plastic deformation in metal-matrix composites with micron size reinforcements.