Fatigue behaviour of plain woven CF/epoxy composites using spread tows (effect of tow thickness on crack formation)

Abstract

This paper discussed fatigue behavior of plain-woven CFRP using very thin and wide tows called spread tows. Tension-tension fatigue tests were conducted and internal damage was observed by using an optical microscope. Three points bending tests were conducted to measure critical energy release rate and threshold energy release rate range. The experimental results showed that the fatigue life of plain-woven CFRP using spread tows was longer than that of conventional plain-woven CFRP. As the fatigue tests were conducted at cyclic maximum stress of 600 MPa (about 65% of tensile strength), we could not observe any cracks in new type plain-woven CFRP that was subjected to 106 cyclic loads. The critical energy release rate and the threshold energy release rate range at spread tow in the composite got higher than those at conventional tow. The ply failure strain, which was the crack formulation and propagation criterion, was calculated by assuming that a part of plain-woven CFRP using spread tows was (0/90)s cross-ply laminate. It was concluded that crack was constrained by using spread tows for the composites.