Evaluation of fatigue damage of woven GFRP laminate by dynamic properties

As Glass Fiber Reinforced Polymers (GFRP) have increasingly been used in civil infrastructures construction, their mechanical properties have received more and more attention. Although its performance under static loading has been studied widely, experimental and analytical research on its dynamic response is still insufficient. In particular, the relationship between fatigue damage occurring in woven cloth GFRP and its dynamic properties has not been quantitatively evaluated. Therefore, by carrying out impact and fatigue loading tests, investigated in this study is the variation of dynamic properties on GFRP orthogonal laminate with fatigue damage. The experiments revealed that the damping ratio of GFRP laminates with both 0/90 degrees fibers and +/- 45 degrees fibers showed an increasing trend with the number of loading cycles, while the natural frequency showed a decreasing trend. Based on this trend, this study proposed a method to monitor fatigue damage progression of the material through the variation of natural frequencies. The decreasing trend of natural frequency could be simulated well by the theoretical model proposed in this study. Furthermore, based on previous studies and the experimental results of this study, a new frequency-based damage index to monitor GFRP's fatigue life was proposed.