Growth behavior of short fatigue cracks in a unidirectional SiC fiber-reinforced titanium matrix composite under spectrum loading

Abstract

In metal matrix composites, the propagation of matrix crack normally leads to load redistribution within the fiber and matrix. The variation of matrix load, on the other hand, affects the growth of the crack in the metal matrix. In this paper, an approach to predict the matrix crack growth rate of a unidirectional SiC fiber-reinforced titanium matrix composite (TMCs) during spectrum loading is developed. The matrix crack was regarded as a mode I central crack. The effects of crack closure and high load hysteresis caused by the variability of were considered. Based on the Forman model, the matrix crack growth rate was also obtained. The results show that the growth rate of matrix crack decreases with the increase of the number of cycles, which can be attributed to the decrease of the stress intensity factor of the matrix crack resulting from the decrease of the load exerted on the matrix. The decreased load of the matrix was caused by the increase of the fiber bridging stress and the redistribution of the stress within the composite when the matrix crack length increases.