Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ∼100 displacements per atom

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradationof material properties under intense neutron irradiation is a critical feasibility issue. This studyevaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite,reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-NicalonTM Type S SiC fiber, following neutronirradiation at 319 and 629 °C to ∼100 displacements per atom. Both the proportional limit stress and ultimateflexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at319 °C, the quasi-ductile fracture behavior of the nonirradiated composite became brittle, a result that wasexplained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphasedue to irradiation. The specimens irradiated at 629 °C showed increased apparent failure strain becausethe fiber/matrix interphase was weakened by irradiation-induced partial debonding