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Numerical and experimental analyses of composite bonded double-strap repairs under high-cycle fatigue

ABSTRACT This work addresses the behaviour of double-strap repairs of carbon-epoxy laminates under high-cycle fatigue loading. Experimental static and fatigue three-point bending tests were performed considering simpler double-strap bonded joints. Numerical analyses involving a cohesive mixed-mode I+II zone model appropriate for high-cycle fatigue loading considering quasi-static and fatigue degradation in a sole damage parameter were accomplished. The numerical fatigue life prediction and normalised compliance versus number of cycles curve are in close agreement with the experimental results. The numerical model was subsequently used to assess the influence of ±5% variation of several parameters intrinsic to fatigue behaviour on the numerically obtained fatigue lives. It was concluded that the exponent parameter of the modified Paris law is the most influent one. In addition, it was concluded that a concurrent variation of ±5% of all analysed parameters can explain the experimental scatter obtained.