Failure analysis of laminated GFRP composite tubes under hydrostatic stress

Abstract

In this paper, a root clause failure analysis of laminated glass fiber reinforced plastic (GFRP) composite tubes after hydrostatic experiment was performed to find out the effect of microstructure defects on the residual strain of the tubes after unloading. The analysis consisted of three steps: Firstly, microscopic images of failed areas of the GFRP tubes were obtained to analyse the dominated microstructure defects leading to the failure as well as the possible failure mechanisms. Then, a computational finite element model considering the microstructure defects was established to predict the failure initiation pressure and location of the laminated GFRP tubes by incorporating the Tsai-Hill failure criteria. Finally, the recommended ply design and defect size range were calculated by the computational model to improve the hydrostatic mechanical properties of the laminated GFRP composite tubes. The results demonstrated that fiber waviness was a critical factor which would cause the early failure initiation of the laminated GFRP composite tubes even under very low hydrostatic stress. By utilizing the developed computational models, we can improve the mechanical properties of the composite tubes by optimizing the thickness of each ply and controlling the fiber waviness under specific range.