An efficient strategy for the calculation of end effects on composite pipes: The thermoelastic case

Through the study of a linear problem, this paper introduces some of the ingredients that are needed in order to conduct efficient nonlinear calculations on composite pipes under thermomechanical loading in the presence of defects. Based on the observation that the main degradation scenarios take place at the extremity of a pipe, a refined model is used to describe this end zone while the rest of the pipe is described using a beam model. In order to avoid creating spurious effects in connecting the beam theory and the 3D end model, the Saint-Venant solution is used as the boundary condition on the latter. This solution is achieved through what is called the exact beam theory [Ladevèze and Simmonds, New concepts for linear beam theory with arbitary geometry and loading, Eur. J. Mech. Solids 1998;17(3):377]. In order to obtain the solution efficiently, the 3D end problem is uncoupled through a dedicated Fourier series expansion into a series of 2D problems. This proposed representation is dealt with efficiently thanks to the use of fast Fourier transforms.