Stability of Eccentric Compression for Aluminum Foam-Filled High-Strength Aluminum Alloy Square Tubes

Abstract

High-strength aluminum alloy thin-walled members under eccentric compression are prone to coupled local-global buckling that limits their load-bearing capacity, yet effective enhancement strategies for this specific loading condition remain insufficiently explored. This study experimentally and numerically investigates the stabilizing effect of closed-cell aluminum foam filling on 7075-T6 aluminum alloy square tubes. Twelve specimens (six hollow and six foam-filled) were tested under eccentric compression, followed by validated finite element parametric analyses covering slenderness ratios of 20–80, width-to-thickness ratios of 5–30, and eccentricities of 5–30 mm. The results demonstrate that aluminum foam filling fundamentally alters the failure mechanism: it provides continuous lateral support that shifts the dominant instability from local buckling to global flexural buckling, while establishing a tube wall-foam synergistic energy dissipation that retards stiffness degradation and enhances ductility. The strengthening effect is strongly geometry-dependent, reaching up to 5.05% in tests and 12.75% in simulations for short columns with 𝜆 ≤ 30 and b/t ≥ 20, but diminishes nonlinearly with increasing slenderness. Notably, the enhancement remains robust against variations in load eccentricity, cross-sectional size, and initial geometric imperfections. Based on 294 numerical simulations, a quantitative criterion-expressed as f(𝜆, b/t) = 𝜆 − 116.30 + 25.06(b/t) − 1.59 (b/t) 2 + 0.04(b/t) 3 —is established to distinguish global buckling from coupled buckling, providing a practical design tool. This study offers both mechanistic insights and an actionable recommendation for applying aluminum foam filling to enhance the eccentric compression stability of high-strength aluminum alloy members.