Stress analysis of metallic thick-walled high-pressure elbows overwrapped with composite material

Abstract

In this paper, Carbon fibre-reinforced plastic (CFRP) is used to reinforce metal elbow, which is a new concept and has the potential to improve the strength of metal elbow. For the elbow, the circumferential stress is the main factor for its failure. In this study, a new stress model of thick-walled high pressure elbow reinforced by composite material is presented to predict the stress distribution. Three-dimensional solid model of elbow is constructed and finite element simulations for the elbow are performed to verify the accuracy of the theoretical model. From the results obtained, the maximum circumferential stress of elbow being reinforced by CFRP is smaller than that of elbow not being reinforced by CFRP. The thinner the wall thickness of metal elbow, the more obvious the effect of CFRP will be. The thicker the wall thickness of metal elbow and the thinner the wall thickness of CFRP, the better the accuracy of stress model will be. When the wall thickness of metal elbow is 25 mm, the deviation is smaller than 4%. Therefore, the new stress model is suited for providing stress expression generally. In addition, failure analysis on metal elbow reinforced by CFRP shows that failure of metal layer is the major cause for failure of CFRP layer, i.e. if the metal layer do not fail, neither do CFRP layer. This provides more proof to justify the accuracy and application of the stress model considering the effect of CFRP.