Microstructure, mechanical properties and thermal shock behavior of 2.5D oxide fiber preform reinforced oxide matrix composites

Abstract

The 2.5D oxide/oxide composites become attractive for their excellent integrity and mechanical properties. The thermal shock resistance performance of the material is very important in the actual high temperature application. In this work, the evolution of microstructure and mechanical behavior of the 2.5D oxide/oxide composites from thermal shock at different temperatures and cycles was investigated experimentally mainly by optical microscope, X-ray computed tomography and macro-mechanical tests. The thermal shock resistance mechanism of oxide/oxide composites was qualitatively explored. The results showed that cracks propagation was the main manifestation of thermal shock damage in composites. Compared with 2D composites, 2.5D composites exhibited the finite domain effect on crack propagation due to its reinforcement had certain fibers in Z-direction. This directly caused the critical thermal shock temperature difference of the 2.5D composites (∼900 °C) was more than twice that of the 2D oxide/oxide composites (∼400 °C). In addition, the finite domain effect also significantly reduced the damage growth rate of the 2.5D composites from cyclic thermal shock, highlighting its excellent thermal shock damage resistance.