Fatigue Behavior and Damage Accumulation of Fiber-Reinforced Plastic Laminatesand Joints

摘要

Aspects of fatigue damage in various fiber reinforced plastic (FRP) laminates arediscussed. Different S-N curves (stress level versus number of cycles to failure) for composite fatigue modeling are presented. Cumulative damage theories applicable to composite materials are investigated. Results of an experimental program in constant and random amplitude fatigue of FRP laminates and joints are presented. Constant amplitude fatigue test results of the FRP laminates indicate a fairly good fit to the traditional power law S-N curve model for cross-ply laminates. In contrast, constant amplitude fatigue tests of angle-ply laminates and bonded, bolted, and bonded bolted joints exhibit significantly less favorable fit to the power law model. Random amplitude fatigue tests show an inconsistent trend as compared to predictions made using Rayleigh approximation. Fatigue life prediction of the laminate specimens tend to be non-conservative for low RMS levels and conservative for high RMS values. The opposite behavior is observed for the joint specimens, where conservative fatigue life estimates are obtained for low RMS levels and non-conservative estimates for high RMS levels.