Tensile behavior of three-dimensional needled carbon fiber reinforced sic composite under load-unload

The monotonic and load-unload tensile behaviors of three-dimensional (3D) needled T300 C/SiC composite were investigated. The results show that the tensile strength and strain of the 3D needled T300 C/SiC composite are 129.6 MPa and 0.61%, respectively. The stress-strain curves of the 3D needled T300 C/SiC composite under monotonic and step tensile loads exhibit a nonlinear behavior, which is caused by the propagation of micro-cracks, debonding and sliding of interfaces, and gradually results in fracturing and the pullout of fibers. This leads to the non-brittle fracture of the composite. The unloading stress levels have a great effect on the residual strain and reloading modulus of the composite. When the stress levels are below 80 MPa, the residual strain linearly increases, while the reloading modulus linearly decreases with increasing unloading stress. And when the stress levels are above 80 MPa, the residual strain increase and the reloading modulus decrease nonlinearly with increasing unloading stress.