Tensile fatigue of a laminated carbon–carbon composite at room temperature Original Research Article

The tensile fatigue behavior of a cross-ply carbon–carbon (C/C) laminate was examined at room temperature. Tension–tension cyclic fatigue tests were conducted under load control at a sinusoidal frequency of 10 Hz to obtain stress–fracture cycles (S–N) relationship. The fatigue limit of the C/C was found to be 213 MPa (93% of the tensile strength), and no fracture was observed at over 104 cycles. The residual tensile strength of specimens that survived fatigue loading was enhanced with increase in fatigue cycles and applied stress. Observations of the fatigue-loaded specimens revealed that the formation of micro-cracks at the fiber–matrix interfaces was facilitated during fatigue loading. These interfacial cracks were concluded to protect the fibers from being damaged by matrix cracks and this behavior was considered to be the governing mechanism of strength enhancement by fatigue loading.