Thermo-mechanical responses of notched layer-to-layer 3D angle-interlock woven composites

Abstract 3D woven composite structures are increasingly replacing metal structures in astronautics and aeronautics areas, due to their excellent mechanical properties and structure integrity. Limitedly, the comprehensive influences of notch and temperature on the mechanical behavior of 3D woven composites have not been completely understood, especially those at elevated temperatures. In this work, the thermo-mechanical behavior and failure mechanisms of centrally notched layer-to-layer 3D angle-interlock woven composites (commonly called notched 2.5DWC, N-2.5DWC) were elaborated by experiment and simulation. Experimental results revealed the elevated temperature strength of N-2.5DWC approximately dropped by 26% compared to the room temperature one. The drop extension of strength was more severe than un-notched 2.5DWC at the same temperature, indicating that the mechanical properties of N-2.5DWC are significantly affected by notch and temperature. A brittle fracture mode without no necking phenomenon was noted, regardless of temperature. However, there was an obvious pull-out damage of yarn near the notch edge, attributed to the comprehensive effect of notch-edge stress concentration and load-bearing warp yarns. Furthermore, a thermo-mechanical predication model for N-2.5DWC was proposed. The mechanical properties at 20 °C and 180 °C were predicted and the damage propagation characteristics were identified, which clearly revealed the damage mechanisms of N-2.5DWC at different temperatures.