CREEP AND CREEP-FATIGUE BEHAVIOR OF CONTINUOUS FIBER-REINFORCED GLASS-CERAMIC MATRIX COMPOSITES

The flexural creep acid creep strain recovery behaviour during creep-f atigue tests of a cross-ply SiC fibre reinforced Barium Magnesium Alum inosilicate glass-ceramic matrix composite was investigated at 1100 de grees C in air. Only heat-treated samples (1 h at 1100 degrees C) were tested. Stress levels of 90, 105 and 120 MPa were examined to produce low strains (<0.4%). A continuously decreasing creep strain rate with values between 1.6 x 10(-6) s(-1) to 4.7 x 10(-8) s(-1) at 120 MPa wa s observed with no steady-state regime. Extensive viscous strain recov ery was found upon the unloading period during the short-duration cycl ic creep (creep-fatigue) experiments. The creep strain recovery was qu antified using strain recovery ratios. These ratios showed a slight de pendence on the stress and cyclic loading frequencies investigated. Th e crept composites retained their ''graceful'' fracture behaviour afte r testing indicating that no (or limited) damage in the matrix was ind uced during creep and creep-fatigue loading.