Out‐of‐plane Tensile Testing and Size‐Dependent Transition in Failure Mechanisms of Thin 2.5D Woven CMCs

ABSTRACT

Reliable out‐of‐plane tensile testing and size‐dependent failure analysis of thin 2.5D woven ceramic matrix composites (CMCs) are essential for thermal structural design but remain insufficiently established. In this study, a self‐aligning fixture and bonding scheme were developed, and room‐temperature out‐of‐plane tensile tests were performed on cylindrical 2.5D woven CMCs specimens with three cross‐sectional sizes. Increasing specimen size reduced tensile strength and promoted a transition from sudden unstable fracture to progressive damage accumulation. This transition may reflect the combined influences of initial defect population, crack propagation, load redistribution, and the number of load‐bearing bundles. Damage may have initiated primarily at pre‐existing defects and intra‐/inter‐bundle pores, subsequently evolving into intra‐bundle cracking, inter‐bundle debonding and peeling, and bundle fracture. Intermediate‐size specimens exhibited transitional features, suggesting possible proximity to a critical transition region.