EFFECTS OF INTERFACE DEGRADATION ON FIBER BRIDGING OF COMPOSITE FATIGUE CRACKS

This paper presents a theoretical analysis that examines the effects of cyclic degradation of interface on fiber bridging of fatigue cracks in metal-matrix or intermetallic-matrix composites. Using fiber bridging models and crack-tip micromechanics results available in the literature, the frictional stresses on individual fiber/matrix interfaces located within the bridging zone in the wake of a fatigue crack in a SCS-6/Ti-6Al-4V composite are calculated. The results are used to demonstrate that a reduction of the interface friction stress by fatigue can lead to a decrease of the fiber bridging stress, and an increase in the near-tip stress intensity range. The consequence is that the near-tip stress intensity range and, thus, the crack growth of a bridged fatigue crack are sensitive to cyclic interface degradation and the distribution of the frictional stress within the bridged zone.