Recent Studies on Micro- and Macro- Mechanics of Composite Materials and Structures

During these few years, several different topics about the microand macromechanics of composite materials and structures have been studied in my research group. They include: defects in composite materials and structures; contact problems; buckling, vibration and control of the composite laminated constructions; aeroservoelasticity of composite wing structures; a novel formalism for the bending theory of anisotropic plates; and failure mechanisms of electronic packaging. The details of these topics are given as follows. 1. Defects in Composite Materials and Structures Defects in composite structures may be produced during manufacture or service. Typical production defects that can occur in the composite component are voids, delaminations, disbonds, foreign body inclusion, incomplete resin cure, wavy fibers, wrinkled layers, etc. All these defects may affect the strength of composites or cause failure of composites. Hence, the search of the defects along with the stress analysis and the study of failure criterion all become important subjects in the community of composite researchers. To analyze the effects caused by these defects, several mechanical models have been developed. Treating the composite materials as homogeneous anisotropic materials and using holes, cracks and inclusions to represent the defects is the most familiar way in mechanics analysis. By this way, several different kinds of problems have been solved by my co-workers and me. My recent studies on defects in composite materials and structures include stress analysis for defect problems, fracture criterion for delamination initiation and identification of holes and cracks. Among these studies, we provided many analytical closed-form solutions for some idealized problems. Using those solutions, we improved our numerical techniques to develop useful numerical softwares for realistic problems. Moreover, through those solutions, we found some useful parameters to establish a meaningful criterion for the delamination initiation. Finally, to match the development of the current smart materials, we proposed a technique for the on-line