Monotonic and Cyclic Loading/Unloading Tensile Behavior of 3D Needle-Punched C/SiC Ceramic-Matrix Composites.

In this paper, monotonic and cyclic loading/unloading tensile behavior of four different 3D needle-punched C/SiC composites are investigated. Under tensile loading, multiple micro parameters of tensile tangent modulus, tensile strength, and fracture strain are used to characterize tensile damage and fracture behavior. Under cyclic loading/unloading, multiple damage micro parameters of unloading residual strain, tensile peak strain, hysteresis loops width, hysteresis loops area, unloading and reloading inverse tangent modulus (ITM) are used to describe the tensile damage evolution. After tensile fracture, fracture surfaces were observed under a scanning electron microscope (SEM). Damage of matrix cracking, interface debonding, fibers fracture and pullout in different plies is observed. Relationships between composite tensile mechanical behavior, damage parameters, and micro damage mechanisms are established. When the fiber volume fraction along the loading direction increases, the composite initial tangent modulus, tensile strength and fracture strain increase, and the unloading residual strain, peak strain, hysteresis width and hysteresis area decrease. For Types 1-4 3D needle-punched C/SiC composite, the fiber volume lies in the range of 25.6-32.8%, the composite initial tangent modulus was in the range of 161.4-220.4 GPa, the composite tensile strength was in the range of 64.4-112.3 MPa, and the composite fracture strain was in the range of 0.16-0.25%.