A Nonlinear Sectional Analytical Model for Predicting the Flexural Response and Failure of Hollow Filament-Wound GFRP Tubes

Abstract

Hollow filament-wound glass fiber-reinforced polymer (GFRP) tubes are known for their high specific strength, corrosion resistance, and structural efficiency. The nonlinear flexural response of these structures is controlled by the interaction of material and stability mechanisms, which are not well-captured by traditional linear sectional approaches. In this paper, a nonlinear sectional analytical model is proposed to determine the flexural response and the corresponding failure modes of hollow filament-wound GFRP tubes subjected to monotonic four-point bending. The formulation combines Euler–Bernoulli beam kinematics, layered numerical integration of the annular cross-section, asymmetric nonlinear tensile and compressive constitutive relations, iterative neutral-axis equilibrium, tangent-stiffness degradation, and compression-side local shell-buckling assessment in a curvature-controlled incremental solution routine. This framework captures progressive stress redistribution, neutral-axis migration, degradation of flexural rigidity and transition from material-controlled compression failure to local shell instability. Validation was performed against experimental results for five filament-wound glass/vinylester tube configurations with nominal ±55° winding and diameter-to-thickness ratios, D/t, ranging approximately from 20 to 75. The predicted load–deflection and moment–curvature responses were in good agreement with the experimental measurements with mean errors of about 1.6% for peak load, 1.8% for ultimate bending moment and 2.4% for peak curvature. The model also reproduces the experimentally observed governing failure mechanisms over the investigated configurations. The convergence study with sectional discretization showed that 200 integration layers provide a good compromise between numerical accuracy and computational efficiency, with less than 1% variation compared to the refined 500-layer reference solution. The proposed reduced-order formulation has low computational cost in the present implementation and provides a direct physical interpretation of the evolving sectional response. Because a directly comparable finite-element runtime was not reported for the benchmark model, no quantitative FE speed-up factor is claimed. Thus, the proposed framework provides an efficient analytical tool for the nonlinear flexural evaluation of hollow filament-wound GFRP tubes in the validated geometric, loading and laminate domain.