Buckling analysis of thin‑walled composite cylinders under hydrostatic external pressure

This study investigates the primary and secondary buckling behavior of thin-walled composite cylinders subjected to external pressure using analytical formulations and finite element (FE) modeling. A refined analytical model is developed to estimate the primary buckling pressure, incorporating geometric effects and mode-interaction features not captured by existing relations. Comparison with FE benchmarks reveals that the proposed correction factor generally reduces the systematic discrepancies observed in conventional analytical methods over the investigated range of cylinder geometries. The results uncover that composite cylinders with higher aspect ratios exhibit a markedly greater susceptibility to secondary (local) buckling than to primary (global) buckling, contradicting the common assumption that global buckling governs thin-walled configurations. Another notable observation is that intralaminar failure may precede buckling in certain lay-up configurations, despite the cylinder remaining globally stable—an outcome not anticipated by classical design formulas. A parametric study further demonstrates that lay-up sequence and diameter strongly influence the critical pressure of primary buckling.