TENSION-TENSION FATIGUE OF A CROSS-WOVEN C SIC COMPOSITE/

The tension-tension fatigue behavior of a cross woven C/SiC composite was studied in terms of damage modes and damage development. The fatig ue stress versus life diagram (S-N) curve and an endurance limit of 32 0-340 MPa (about 80% tensile UTS) for 10(6) cycles were obtained for t he C/SiC composite. Different fatigue behaviors were found for samples that failed during fatigue and for samples that survived 10(6) cycles . Seven fatigue damage modes were observed, the development of which w ere used to explain the different fatigue behaviors. For the fatigue-f ailed samples, the degrees of damage of the seven modes increased with increase of cycles, leading to an increase in elapsed strain and a de crease in composite modulus. For fatigue-survived samples, the develop ment of all the damage modes except for fiber breaking caused an initi al increase of elapsed strain and decrease of composite modulus, but a t high cycles, fiber bundle realignment and straightening in these sam ples led to partial recovery of the modulus and cessation of the damag e development. (C) 1997 Elsevier Science S.A.