Foreign object damage and post-impact tensile behavior of plain-woven SiC/SiC composites

Abstract

Plain-woven SiC/SiC composite plates, fabricated using the chemical vapor infiltration (CVI) technology, were impact-tested at different velocities using 3-mm-diameter steel spheres. The states of the impacted targets were divided into three categories: surface damage, critical penetration, and full penetration. The microstructures of the foreign object damage (FOD) in the targets were carefully observed using microscope and X-ray computerized tomography (CT) scans. Based on the results of the observations, the forms of impact damage of ceramic matrix composites (CMCs), including cone cracking, yarn fracture and bending, and delamination, are revealed and summarized. The mechanisms of the penetration process were further analyzed by combining these damage modes of the CMCs. Subsequently, tensile tests of the impacted specimens were performed to investigate the effect of FOD on the tensile behavior of the CMCs. The digital image correlation (DIC) method was used to obtain the strain distribution of the impacted targets during tension. The tensile curves of the undamaged and impacted specimens were obtained and compared. The evolution of the tensile failure of the damaged beams was then analyzed. Finally, the residual strengths of CMC plates impacted at different velocities were compared.