Effects of tensile fatigue loading on flexural strengthof 3D integral braided C/C composites

摘要

The flexural strength of 3D integral braided C/C composites after tensile fatigue loading at various numbers of cycles wasexamined. The results show that the flexural strength of specimens is enhanced with increase in tensile fatigue cycles. Theenhancement of flexural strength is visible exceeding tensile fatigue cycles 102 and can increase by 40% comparing with theoriginal specimens at 105 fatigue cycles, but the fatigue enhancement is not boundless and will decline gradually after 105cycles. Observation of the fatigued specimens revealed that the formation of micro cracks at the fiber-matrix interfaces isfacilitated during tensile fatigue loading. These interfacial cracks can protect the fibers from being damaged by matrix cracksand lead to fiber bundles and fibers pull-out, which will absorb and dissipate mechanical energy from flexural loading, so thisbehavior was considered to be the governing mechanism of strength enhancement by tensile fatigue loading.