Fatigue Life Predictions in Woven Carbon Fabric/Polyester Composites Based on Modulus Degradation

Abstract

An analytical model, based on stiffness degradation during fatigue loading, which has been used for fatigue life 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.

Fatigue models for woven textile composite laminates

“…Khan, Al-Sulaiman, Farooqi, and Younas (2001) published a fatigue study on pre-preg plain weave carbon/polyester composites. Tests were done on three different layups at a stress ratio R of 0.1 and a testing frequency of 20 Hz.…”

The fatigue of carbon fibre reinforced plastics - A review

“…Khan et al [313] proposed a stiffness reduction model where they created a damage variable, D, that related to stiffness in the following way:…”

A Stiffness Degradation Based Fatigue Damage Model for FRP Composites of (0/θ) Laminate Systems

“…GRP composite specimens with a volume fraction of 33.8% were tested with the stress ratio of 0.1 under cyclic stress amplitudes of 85 MPa and 95 MPa. CFRP (0/45) laminates with a volume fraction of carbon fibers V f =67% were tested [26] under a maximum cyclic stress of 245 MPa and stress ratio of 0.1. Figures 7 and 8 show that experimental fatigue damage data of (0/45) composite laminates fall between the predicted damage curves of 0°ply and 45°ply over fatigue cycles.…”

“…Predicted fatigue damage curves for 0°and 90°plies as number of fatigue cycles increases versus experimental data of CFRP (0/90) composite plies under stress amplitudes of a 424.8 MPa and c 662 MPa b and d predicted damage curve of (0/90) CFRP composite based on Eq (5) vs (Predicted fatigue damage curves for 0°and 45°plies as number of fatigue cycles increases versus experimental data of CFRP (0/45) composite plies with V f =67% tested with R=0.1 under stress amplitudes of a 245 MPa and b predicted damage curve of (0/45) CFRP composite based on Eq (5) vs (0/45) composite experimental data[26] …”