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

An analytical model, based on stiffness degradation during fatigue loading, which has been used for fatigue hfe predictions in the Fiber Reinforced Plastics (FRP), is employed to examine its validity to the fatigue life predictions in the Woven Fabric Reinforced Plastics. The rate of stiffness degradation (dE/dN) has been obtained from the constant amplitude fatigue testing of 8-ply coupons made from prepreg plainweave woven carbon fabric having a polyester resin as the matrix material. The test coupons had three different 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 estimated fatigue lives obtained from the damage rate function dD/dN, which in turn was a function of the stiffness degradation rate dE/dN, were compared with the experimentally observed fatigue life data. It is shown that the stiffness degradation model provides reasonably good correlation between the analytically determined fatigue lives and the experimentally observed fatigue lives for the plain-weave woven Carbon Fabric Reinforced Plastic Composites.