A dedicated computational strategy for composite pipes: Basic principle and illustration

In this paper we aim to solve the problem of the tolerance of composite pipes to end defects. The main issue with such defects is delamination, and its predictive calculation requires refined 3D computations. For a family of defects, such types of analyses lead to very high computation costs. Therefore, we sought an efficient computational strategy dedicated to composite pipes. This strategy is presented in this paper in the linear elastic case. Because the degradations are localized at the end of the pipe, only that part is modeled finely., while the center of the pipe is modeled using a beam theory. The strategy can be divided into two main steps. The first step consists in calculating the Saint-Venant solution of the elastic problem in order to connect the beam to the 3D end zone correctly. This Saint-Venant solution is obtained through what is known as the exact beam theory. The second step consists in solving the 3D end problem loaded with the solution of the interior part of the pipe (Saint-Venant solution). In order to reduce the cost of this 3D resolution, a dedicated Fourier series expansion is used to uncouple the 3D problem into a set of 2D problems. Finally, Fast Fourier Transform is used to transfer the different fields from the 3D state to the 2D form. This strategy is illustrated on a {[}55/-55/0/-55/55] pipe made of G969/RTM6 fabric plies.