Study on Composite Material Failure of Reinforced Thermoplastic Pipes under External Pressure

This paper examines the mechanical properties of reinforced thermoplastic pipes (RTP) under the influence of external pressure. We used the three-dimensional (3D) thick-walled cylinder theory, combined the 3D Hashin failure criterion with the theory of the evolution of damage in composite materials, considered their nonlinear mechanical behaviors, and introduced changes in the winding angle caused by deformation to formulate a model for the progressive failure analysis of RTP. The model was used to examine the failure sequence and external pressure capacity of RTP, and its correctness was verified by a finite element model. The results show that increasing the winding angle of RTP within a certain range can improve its external pressure capacity. When the winding angle exceeded ±50°, the failure of the RTP under external pressure mainly depended on the fiber fracture of the reinforced layer. With an increase in the ply number of the reinforced layer, the external pressure capacity of the RTP increased nonlinearly and its rate of growth gradually decreased.