The analysis of debonding damage between steel tension wire and epoxy resin in flexible end fitting under cyclic loading

Flexible pipe end fitting is a structure connecting flexible pipe and mental flange, which is a transition between flexible structure and rigid structure. Epoxy resin is used to fix tension steel wire in the end fitting. The bonding interface between epoxy resin and tension steel wire is prone to debonding when flexible pipe end fitting is used under cyclic loading. The damage of bonding interface is mainly due to the cumulative effect of cyclic loading. The damage of epoxy resin can cause temperature changes, which can affect the material properties of the resin and then affect the bonding strength. In this paper, the relationships between cycle numbers of epoxy resin and temperature, temperature and elastic modulus are obtained through fatigue analysis and dynamic mechanical analysis (DMA). The fatigue model is established based on the relationship between the modulus of epoxy resin and temperature. Based on the fatigue model, the bonding damage between steel tension wire and epoxy resin is obtained by finite element analysis (FEA). The results show that it is feasible to characterize the fatigue damage between steel tension wire and epoxy resin by temperature. This work provides a new method for predicting the fatigue of tensile steel wire and epoxy resin in end fitting.