Effect of He pre-implantation and neutron irradiation on mechanical properties of SiC/SiC composite

Mechanical property changes of SiC/SiC (Hi-Nicalon/C/SiC) composite caused by uniform He pre-implantation up to about 170 at.ppm at 400-800 deg. C followed by neutron irradiation up to about 7.7 x 1025 n/m2 (En>0.1 MeV) at 800 deg. C in HFIR were investigated by the three-point bend tests and nano-indentation tests. Degradation of the composite bend properties due to neutron irradiation was observed. The hardness increased after neutron irradiation for both the SiC-matrix and the Hi-Nicalon fiber. There was almost no change in the elastic modulus of the SiC-matrix, but there was an increase in the modulus of the Hi-Nicalon fiber after neutron irradiation. He pre-implantation had almost a negligible effect on the mechanical properties of the composite specimen