9523078 Yee This project is to advance the development of fracture-resistant engineering plastics and polymer-matrix composite materials. It will develop fundamental knowledge in the science of toughening, and will provide guidance to the polymer industry in product development and safety. Shear-yielding toughening via rubber particles and micro-cracking/crazing/bridging toughening via thermoplastic particles are the two most important toughening methods used to improve material performance. A fundamental connection between these two mechanisms is the intrinsic stress state dependent deformation of polymers. Identification of the stress state near the reinforcing particles and characterizing the deformation of the matrix in this stress state are critical issues. These issues can only be resolved through experimental studies of the polymer deformations and quantitative analyses of the details of the toughening mechanisms. ***
