Experimental and computational meso-scale investigation on the deformation and failure behaviors of plain woven SiC/SiC with intrinsic and manufactured defect

Abstract

For plain woven SiC/SiC composites used in aerospace thermal-structural applications, not only the pristine material properties but the open-hole performance are of critical concern for the components in service. This study investigated the influence of intrinsic pores induced during SiC matrix preparation and manufactured holes on the macro mechanical properties of plain woven SiC/SiC through experimental and numerical methods. Tensile tests at room temperature were conducted on SiC/SiC specimens with different hole apertures and configurations, and the digital image correlation (DIC) method was employed for full-field strain measurement. Moreover, micro-computed tomography (μ-CT) was utilized to characterize the internal microstructure, original defects, and failure fractures. Based on the reconstructed mesoscale model, the tensile strength and failure mechanisms of pristine and open-hole specimens were predicted and analyzed, with the models validated against the experimental results. The results showed that the inter-tow defects play an important role on the deformation and failure of pristine SiC/SiC specimens during tensile loading. The notch strength results indicated that SiC/SiC exhibits weak notch sensitivity, and the local mesoscopic deformation of the notch is affected by the combination of macroscopic stress gradients and mesoscopic structures. The mesoscale simulation results showed that the position of the hole has a significant impact on the strength of the single layer SiC/SiC composite. The more the notch invades the warp, the greater the decrease in load-bearing capacity, and the relative position of the weft mainly determines the crack propagation path. The failure mode in the simulation results is consistent with the experimental findings, indicating that the simulation model, which considers the weave architecture, can better explain the notch failure behavior of Ceramic Matrix Composites (CMCs).