Fatigue behaviour of cross-ply Nicalon/CAS-II glass–ceramic matrix composite at room and elevated temperatures

Abstract

Abstract An experimental study was carried out on cross-ply Nicalon/CAS-II glass–ceramic matrix composite under monotonic, static, cyclic and a combination of static and cyclic loadings. Tests were carried out at room temperature (20 °C) and 800 °C in air with varying levels of peak stress, stress ratio and loading history. At room temperature and 800 °C, the composite exhibited fatigue limit (10 6 cycles) at 40 and 20% of the room temperature flexural strength, respectively. Therefore, the fatigue limit of the composite at 800 °C reduced to half of its room temperature value. The composite also exhibited a shorter lifetime under cyclic loading than under static loading at 800 °C. Although the residual strength of the specimens those survived 10 6 cycles at 20 °C was ∼15% lower than the original flexural strength, the residual strength of the specimens those survived 10 6 cycles at 800 °C was ∼20% higher than the corresponding flexural strength. It indicates that the fatigue damage mechanisms at 20 °C is different from that at 800 °C. Parameters such as peak stress, stress ratio and loading history were also found to play strong role on the fatigue damage mechanisms of this composite.