Effect of high-temperature preloading on tensile properties and failure mechanisms of SiC_f/SiC composites

Understanding the evolution of mechanical properties and damage mechanisms of SiC_f/SiC composites under multi-field coupling environments is essential for ensuring their safety and reliability in aerospace applications. This study investigates the tensile properties and failure mechanisms of 2D plain-weave SiC_f/SiC composites from room temperature to 1400 °C, with a particular focus on the influence of high-temperature preloading. Through macroscopic and microscopic morphology analysis, the key factors affecting tensile strength and failure mechanisms were systematically examined. The effects of the magnitude and holding time of high-temperature preloading on the tensile properties of SiC_f/SiC composites were also explored, revealing significant impacts in the medium-temperature range. The results indicate that the tensile strength and matrix cracking stress decrease approximately linearly with increasing temperature for samples without high-temperature preloading. However, the difference in tensile strength between samples with and without high-temperature preloading diminishes as temperature increases. The degradation of component properties in SiC_f/SiC composites and high-temperature oxidation contribute to the decline in their tensile strengths. The healing of surface cracks induced by rapid oxidation at 1400 °C significantly reduces the impact of high-temperature preloading. A physics-based theoretical model for their high-temperature tensile strengths was established. This research provides valuable insights for evaluating the tensile properties of SiC_f/SiC composites under thermal-mechanical-oxygenic coupling environments.