Design optimization and performance verification of continuous GF/PEEK composite RTP pipes based on multi-scale theory

Abstract Glass fiber reinforcement is widely used as a strengthening method for thermoplastic composite pressure pipes, with key factors being the selection of reinforcing materials and the rational distribution and transfer of interlayer stresses. This study focuses on continuous glass fiber-reinforced polyetheretherketone (PEEK) composite flexible reinforced thermoplastic pipes (RTP), analyzes their structural models, stress states, and failure factors, and investigates the synergistic load-bearing mechanisms and long-term service performance of their multi-layer composite structures. Based on the interlayer stress transfer theory of RTP pipes, a multi-scale constitutive model incorporating the anisotropy of fiber-reinforced layers and interfacial damage evolution was established. This model reveals the critical conditions and failure paths of interfacial debonding under operational conditions.