Buckling and material failure in thermoplastic composite pipes under thermo-mechanical loading

This study analyses the buckling and material failure behaviour of thermoplastic composite pipes subjected to combined mechanical (internal and external pressures, bending moment and axial compression) and thermal loads, typical of deepwater offshore operational applications. Numerical simulations were conducted using temperature-dependent material properties for AS4/APC-2 carbon/PEEK laminates and APC-2 PEEK liners, to evaluate the effect of thermal gradient. Findings indicated that increasing internal pipe surface temperatures intensifies thermal gradients and reduces buckling and material failure resistance, with the inner liner being the most affected due to its proximity to elevated temperatures. The failure mode changes from buckling to material failure, driven by the plastic yielding of the inner liner, at approximately 70°C. Design strategies incorporating robust insulation, material and geometry optimisation as well as thermal management are proposed to enhance the structural integrity of the TCPs in deepwater operating conditions.