In situ damage propagation and fracture in notched cross-ply SiC/SiC composites: Experiment and numerical modeling

In this paper, the damage progression and fracture behavior in notched cross-ply SiC/SiC composites were investigated using the in situ digital image correlation (DIC) and acoustic emission (AE) techniques. Under tensile loading, the mechanical properties of composite's elastic modulus, proportional limit stress (PLS), ultimate tensile strength (UTS), and fracture strain were obtained for non-notched, single-hole, double-holes, and four-holes samples. Based on the analysis of composite's tangent modulus, the nonlinear tensile stress-strain curves were divided into three main domains, relating with internal multiple damage mechanisms observed using the in situ DIC and AE. Effects of the number and location of the circular holes on the full-filed composite's damage and strain evolution, AE energy and ring-down count were investigated. After tensile fracture, the composite's macro fracture morphology and micro damage mechanisms were observed under the scanning electronic microscopy (SEM). Numerical modeling of tensile damage and fracture process of different notched samples were conducted using the extend finite element method (XFEM). Relationships between the notch types, tensile mechanical properties, macro strain evolution, and micro damage mechanisms were established.