Strain response of C/SiC composite to thermal and mechanical load cycling in oxidising atmosphere

摘要

Strain response of a C/SiC composite simultaneously subjected to thermal cycling (1173 centre dot 1473 K) and mechanical cycling (60 + 20 MPa) in an oxygen centre dot argon mixture: 10 centre dot 4 percentO_2-89 centre dot 6 percentAr was investigated. Thermal strain with maximum value of approx 0 centre dot 117 percent and mechanical strain with maximum value of approx 0 centre dot 0 centre dot 29 percent were directly measured on a progressively increasing baseline strain from 0 centre dot 354 to 0 centre dot 670 percent. The thermal strain and mechanical strain were found to have an approximately linear relationship with the temperature and stress respectively; and to be in quantitative agreement with the calculated results using the proposed semiempirical formulas. The baseline strain was considered to be damage dependent and could increase with accumulated damage. It is observed that the thermal and mechanical load cycling in an O_2-Ar mixture could cause the coating/matrix cracks, the degradation of the interfaces, fibre oxidation, and an increase in the baseline strain of the composites by widening crack opening displacement due to larger interfacial debonding and fibre sliding, and reducing effective load bearing area of the fibres.