Cyclic loading of a SiC-fiber reinforced ceramic matrix composite reveals damage mechanisms and thermal residual stress state

Abstract

This study reports on the effects of axial thermal residual stresses, cyclic loading and presence of notches on the tensile performance of a SiC-fiber-reinforced barium–magnesium–alumina–silicate (BMAS) ceramic matrix composite. The residual stress state of the composite was experimentally measured by interrogation of the tensile curves at a uniquely well-defined common intersection point of unloading–reloading cycles in the tensile domain. Notch presence was critical on the material’s mechanical response and promoted catastrophic failure shortly after the achievement of a saturated matrix crack state. The result of cyclic loading was an increase by 20% in sustainable stress throughout loading, as compared to pure tension. Scatter in elastic properties within specimens of different notch-to-width ratios was reconciled with theoretical expectations by application of a translation vector approach in the stress–strain plane, based on the material’s residual stress state. Acoustic emission and infrared thermography provided valuable insight into damage identification, location and sequence.