Transient thermomechanical axisymmetric analysis of multilayer thermoplastic composite pipes

Abstract

Thermoplastic composite pipe (TCP) is a promising design concept for offshore sour oil fields. The bonded structure typically consists of inner and outer homogeneous isotropic polymeric layers and intermediate transversely isotropic laminate ply layers. A theoretical transient thermomechanical analysis under axisymmetric loadings and thermal gradient subjected to convective heat transfers at the inner and outer surfaces is presented. For the heat conduction problem in a multilayer composite pipe, the transient temperature is expressed as a combination of steady state and filtered homogeneous transient solutions employing Bessel's functions. The general solution for the TCP thermomechanical axisymmetric model is also derived. An instantaneous temperature interpolation of the exact interlayer values is employed for the thermal stress analysis to overcome the difficulty of the double integration of Bessel's functions. The von Mises stress and Maximum Stress are respectively applied as failure criteria for the isotropic and laminate layers. During the warming up and cooling down, the through-thickness temperatures and stresses gradually progress from the initial towards the final steady state regime. The thermomechanical transient response is dominated by mechanically induced stresses. The transient failure indexes are below the initial and steady state values for the axisymmetric mechanical and thermal loadings during the selected warm up or cool down conditions.