Fatigue life predictions in woven carbon fabric/polyester composites basedon modulus degradation

An analytical model, based on stiffness degradation during fatigue loading, which has been used for fatigue life predictions in the Fiber Reinforced P lastics (FRP), is employed to examine its validity to the fatigue life pred ictions in the Woven Fabric Reinforced Plastics. The rate of stiffness degr adation (dE/dN) has been obtained from the constant amplitude fatigue testi ng of 8-ply coupons made from prepreg plainweave woven carbon fabric having a polyester resin as the matrix material. The test coupons had three diffe rent ply stacking sequences, namely, the unidirectional (0)(8), and two off axis plied (0,0,+45,-45)(s), and (+45,- 45,0,0)(s) orientations. The estim ated fatigue lives obtained from the damage rate function dD/dN, which in t urn was a function of the stiffness degradation rate dE/dN, were compared w ith the experimentally observed fatigue life data. It is shown that the sti ffness degradation model provides reasonably good correlation between the a nalytically determined fatigue lives and the experimentally observed fatigu e lives for the plain-weave woven Carbon Fabric Reinforced Plastic Composit es.