Analyzing Bending Damage Mechanical Properties of Multi-Layered Wound Composite Pipes

Abstract

An accurate analysis of bending properties is essential for understanding the damage behavior of multi-layered composite pipes. Currently, two-dimensional theoretical models based on the Lekhnitskii stress function or complex expressions with unknowns are primarily used to analyze the bending characteristics of composite pipes. These approaches cannot accurately predict the stress distribution of every layer and initial damage in composite pipes under bending conditions. In accordance with nonlinear cylindrical shell theory, this study parameterizes the ellipticity deformation in each layer and establishes the constitutive equation of pipes while considering material nonlinearity and the stiffness degradation model. The virtual work principle and failure criterion are applied to develop a three-dimensional (3D) mechanical analysis model to assess the bending properties of pipes. A four-point bending test and numerical simulation are carried out to validate this theoretical model. On this basis, the stress distribution, stiffness degradation mechanism, and damage failure characteristics of pipes under bending conditions are analyzed. The findings accurately characterize the 3D stress state of pipes under bending conditions and reveal the process of stiffness degradation and damage failure. This study enhances the understanding of composite pipe behavior under bending conditions and sheds more light on enhancing creditability in offshore applications.

Keywords: Composite pipes, Bending property, Stiffness degradation, Damage failure