Fatigue of Quasi-Isotropic Laminated Composite Cylinders Under Tension-Tension Loading

Life prediction techniques for structural composites are based on test data obtained from coupon specimens. A tension fatigue life prediction methodology based on a through-thickness damage accumulation model is used to predict the fatigue failure of composite coupon specimens. Its applicability to thin-walled cylindrical specimens is in vestigated by comparing the fatigue behavior of composite coupon specimens to that of composite thin-walled cylindrical specimens. AS4/3501-6 graphite-epoxy coupon speci mens and thin-walled cylinder specimens with the same layup sequence of [0/ ± 45/90]s were tested under static and fatigue loading conditions. Reasonably good agreement is found between the measured and predicted lives of the coupon specimens. Although the ultimate stresses of coupon and cylindrical specimens are different, it is observed that their fatigue lives at the same percentage of ultimate stress are nearly identical, independent of the coupon edge effect. It is concluded that the fatigue life prediction methodology for coupon specimens could be extended to estimate the fatigue life of the thin-walled graphite/epoxy composite cylinders used in this study