This interdisciplinary research will investigate the mechanical behavior of model joints in metal matrix composites and its relationship to defects and microstructural features developed during processing. Research will focus on joint geometries commonly found in designing with advanced materials, including both composite-composite and composite-monolithic combinations. Fiber coatings will be used to control the interfacial characteristics of the composites and to develop an understanding of end effects in weakly and strongly bonded systems. Particular emphasis will be placed on the evolution of defects and relevant microstructural features during diffusion bonding, and their role in deformation micromechanics and properties of the joint. Tests will be conducted at elevated and ambient temperatures under various loading conditions and the results related to emerging constitutive laws developed for monolithic and for composite materials. This research should assist in the construction of predictive models for the behavior of joint systems using the principles of micromechanics and processing science.