Analytical model for stress and deformation of multiple-winding-angle filament-wound composite pipes/vessels under multiple combined loads

An multi-angle filament wound(FW) model is proposed under pressure, torsion and axial loads (multiple combined loads), which can calculate stresses and displacements of arbitrary multi-layers and bring more uniform strength though FW wall thickness. Based on orthotropic constitutive relation and axisymmetric thick-walled cylinder theory, a three-dimensional (3D) analytical solution for deformations and stresses of multi-angle FW pipes/vessels is presented. First, the stresses of fiber layer in cylindrical coordinate are obtained. Then, the deformations and stresses of each orthotropic winding layers, including longitudinal stresses σ₁, transverse stresses σ₂, σ₃ and shear stresses τ₁₂ are obtained, respectively. Moreover, the effect of shear extension coupling is taken into consideration because it is impossible for the ±ϕ winding angles to exist in the same radius. Subsequently, the proposed formulae are verified by numerical and experimental examples with finite element method (FEM). Results show that our new method calculates accurate stresses of FW pipes/vessels under multiple combined loads, which provides a theoretical foundation for damage analysis and optimization for FW structures.