Off-axis crack-coupled failure model and mechanical properties of flexible composite materials

Fiber-reinforced flexible composites are critical materials for stratospheric airship envelopes owing to their excellent mechanical properties and weather resistance. To address the challenge of coupled off-axis and crack-induced failures throughout the entire manufacturing-service cycle, this study overcomes the traditional research limitation of treating “damage-free off-axis strength prediction” and “single-angle tear strength analysis” as separate issues. Based on the Tsai–Hill failure criterion, we propose a synergistic theoretical framework that incorporates dual parameters: off-axis angle and crack length. By introducing an off-axis angle factor and integrating a single-angle failure model, a new failure model that couples multiple damage mechanisms was developed. Uniaxial tensile tests were conducted systematically under varying off-axis angles and crack lengths, and the results demonstrate that the proposed model provides high prediction accuracy and reliability.