Numerical and experimental study of tensile mechanical behavior of 2.5D woven C_f/Al composites at high temperature

2.5D woven composites show great promise for aerospace applications owing to their high specific strength, high specific modulus and good delamination resistance. However, there is a dearth of research on their mechanical properties and failure behaviour at high temperature environment. This paper presents numerical simulation and experimental study on the quasi-static tensile mechanical response and failure behaviour of 2.5D woven C_f/Al composites at high temperature (400 ℃). Representative unit-cell models at the micro- and meso-scale are constructed based on the microstructure and periodic arrangement characteristics of the yarn. Based on the temperature-related material parameters of the matrix and interface, a multiscale finite element model is established to numerically analyse the thermal stress distribution as well as macroscopic and mesoscopic mechanical behaviour of the composites at high-temperature environment. The high temperature induces inhomogeneous thermal stress distribution in the composites, where the matrix and yarns are subjected to compressive and tensile stress, respectively. The experimental results show that the tensile modulus, ultimate strength and elongation of the composites are 63.7 GPa, 238 MPa and 0.72%, respectively. The numerical tensile stress-strain curve is generally consistent with the experimental results. Numerical simulation results show that the matrix and interface damage that induced by the thermal stresses accumulates and expands gradually during the tensile process. This results in the emergence of local interface debonding at the initial tensile stage. As the tensile strain increases, the composites successively experience the local failure of warp yarns and transverse cracking of weft yarns. At the final stage, the severe axial fracture of warp yarns leads to catastrophic fracture of the composite, resulting in a dramatic drop of the tensile stress curve. The fractured warp yarn exhibits a rough fracture surface with the characteristics of fibre pull-out and matrix alloy tearing.