Energy absorption mechanism of aluminum foam sandwich structure against bird impact and its application in impact protection bulkhead inside airplane nose

Overview

This research addresses the weight limitations of conventional aluminum alloy stiffened baffle plates in civil aircraft nose end frames by developing and evaluating an aluminum foam sandwich structure designed to withstand bird strike impacts. The proposed design features an asymmetric panel configuration comprising a highly ductile 2024-T3 aluminum alloy upper face sheet, a high-strength 7075-T6 aluminum alloy lower face sheet, and an intermediate aluminum foam core layer. The investigation focuses on characterizing the energy absorption mechanisms of this sandwich structure during bird impact events and comparing its performance against traditional stiffened panel configurations currently employed in civil aircraft.

Methods and approach

The research employed computational simulation validated against experimental data to assess bird strike resistance. Initial validation established the accuracy of the bird body constitutive model and contact algorithm through comparison of high-speed impact test data on aluminum alloy flat plates with simulated strain outputs. Constitutive models for both homogeneous and gradient aluminum foams were verified using parameter inversion methods combined with existing experimental data. Transient impact dynamics simulations of bird strikes were conducted using Pam-crash software for both conventional stiffened panel structures and the proposed aluminum foam sandwich structure. The comparative analysis examined damage patterns, deformation characteristics, and energy absorption data across both structural configurations. A full-coverage optimization design scheme for the baffle plate was subsequently developed based on the characterized energy absorption properties of the aluminum foam sandwich structure.

Key Findings

The analysis revealed distinct energy absorption mechanisms between the two structural approaches. Conventional stiffened panels primarily dissipate bird impact energy through plastic deformation, while the aluminum foam sandwich structure achieves energy absorption through synergistic mechanisms involving compressive collapse failure of the foam core layer and large plastic deformation of the upper face sheet. The optimized aluminum foam sandwich structure demonstrated superior energy absorption efficiency compared to traditional stiffened panel configurations. Full-coverage bird impact simulations indicated that the proposed aluminum foam sandwich baffle design achieved structural weight reduction exceeding 30% while maintaining equivalent bird strike resistance performance to existing in-service structures.

Implications

The demonstrated weight reduction of over 30% while preserving bird strike resistance performance represents a substantial advancement for civil aircraft nose bulkhead design. The identified dual-mechanism energy absorption approach—combining foam core compressive collapse with upper face sheet plastic deformation—provides fundamental understanding applicable to impact-resistant aerospace structural design. The validated computational methodology and material constitutive models establish a framework for future optimization of lightweight protective structures subject to high-velocity impact loading. These findings offer technical foundations for implementing aluminum foam sandwich structures in civil aircraft applications where weight reduction and impact resistance represent competing design requirements.