A method for evaluating the thermal fatigue resistance of ceramics and its application to a fibre reinforced refractory material

An original method of characterizing thermal fatigue of ceramic materials has been proposed. This method is based on after-shock measurements of the degree of damage through a compliance calibration using compact tension (CT) test pieces. This method has been applied to a fibre-reinforced refractory material subjected to repeated thermal shock between 20 and 800° C. It has been demonstrated from both experiments and finite element analysis that the CT specimen is a convenient shape for the evaluation of thermal fatigue behaviour. In these specimens it has been established that the damage primarily affects the notch tip. The thermal fatigue behaviour of the CT specimens depends on notch length: when the notch length is greater than 30 mm, catastrophic failure occurs after a few cycles. When the notch length is less than 30 mm, the crack formed at the notch tip during the first cycle grows slowly during subsequent cycles. This behaviour has been explained by the variation of the stress intensity factor K _I.