Interlaminar Crack Growth Resistances of Various Ceramic Matrix Composites in Mode I and Mode II Loading

Abstract

Interlaminar crack growth resistances were evaluated for five different SiC fiber-reinforced ceramic matrix composites (CMCs) including three gas-turbine grade melt-infiltrated SiC∕SiC composites. Modes I and II crack growth resistances, GI and GII, were determined at ambient temperature using double cantilever beam and end notched flexure methods, respectively. The CMCs exhibited GI=200–500J∕m2 and GII=200–900J∕m2. All the composites (except for one SiC/CAS composite) showed a rising R-curve behavior either in mode I or in mode II, presumably attributed to fiber bridging (in modes I and II) and frictional constraint (mode II) in the wake region of a propagating crack. A glass fiber-reinforced epoxy polymer matrix composite showed typically two to three times greater GI and eight times greater GII, compared to the CMCs. An experimental error analysis regarding the effect of the off-the-center of a crack plane on GI and GII was also made.