Polymer composites were introduced for the aerospace industry as light, strong, stiff materials, and adopted by the construction and automobile industries, among others. Meanwhile, composite materials have been introduced to fulfill the uses that these conventional materials could not, such as in extreme environments. The research for new composites includes not only new polymer systems, but metals, ceramics and intermetallic systems as well. This volume contains a selection of recent work by leading researchers in micromechanics on the topics of prediction of overall properties of elastic, perfectly bonded systems, problems associated with inelastic deformation of the phase, debonding at interfaces and growth of distributed damage. Many familiar aspects of mechanical behavior, such as fatigue, fracture, strength and buckling, etc. have been reexamined and adapted for these new systems.