Radiation effects and micromechanics of SiC/SiC composites (December 1, 1990--November 14, 1993) and modeling the mechanical behavior of SiC/SiC composites in fusion environments (November 15, 1993--November 14, 1996). Final report, December 1, 1990--November 14, 1996

摘要

The development of Silicon Carbide composite materials for structural applications in fusion energy systems is mainly motivated by the prospect that fusion power systems utilizing the material will have a much more favorable environmental impact. The research team at UCLA was the first to identify the potential advantages of SiC/SiC composite materials through early System Studies. Consequently, two three-year term grants have been awarded to the team, in order to focus on modeling the effects of irradiation on key properties that have been recognized by the community as fundamental to the successful development of the composite. Two main tasks, which are further subdivided into several subtasks each, have been pursued during the course of research during the period: December 1990 through November 1996. The first task deals with modeling the effects of irradiation on the dimensional stability of SiC. To achieve this goal, a substantial effort was launched for modeling the evolution of the microstructure under irradiation. Rate and Fokker-Planck theories have been advanced to model the complex multi-component system of SiC under irradiation. The effort has resulted in a deeper understanding of the interaction between displacement damage components, and transmutant helium gas atoms. Utilizing the methods of Molecular Dynamics (MD) and Monte Carlo (MC), the energetics of defects and the basic displacement mechanisms in SiC have been fully delineated. An advanced Fokker-Planck approach was formulated to determine the phase content and size distribution of damage microstructure in SiC. Finally, a rate theory model was developed and successfully applied to the experimental swelling data on SiC. In the second task, the authors investigated the mechanical behavior of SiC/SiC composites under the irradiation conditions of fusion reactors. The main focus of the second task has been on developing models for the micro-mechanics of cracks in the fiber reinforced matrix of the silicon carbide composite. The effects of irradiation on inducing inelastic deformations in the fiber and the matrix were emphasized. Brief reviews for the results of their research are given here, followed by copies of 26 journal publications resulting from the work supported under this grant.