Numerical Modelling of Structural Compromising Events on Various Types of Typical Airframe Structures (Crashworthiness or Bird Strike)

Abstract

The aerospace industry’s transition to monolithic carbon fibre reinforced polymer (CFRP) fuselages has introduced significant weight and fatigue benefits, but also critical vulnerabilities regarding low-velocity impact (LVI) events. Ground support operations pose a statistically high risk of impact damage, particularly to the main deck cargo door (MDCD). Unlike metallic structures, CFRP exhibits barely visible impact damage (BVID), where extensive internal failure can occur with minimal external indication. This thesis addresses the lack of high-fidelity numerical data for full-scale composite cargo doors by developing a multi-scale finite element (FE) model of the Airbus A350F MDCD using Abaqus/Explicit. A semi-monocoque design featuring a monolithic skin and bonded omega stringers was modelled and subjected to impact energies of 5J, 20J, and 40J. The simulation incorporated Hashin’s failure criteria for intralaminar damage and cohesive zone modelling (CZM) for skin-stringer delamination. Results indicate that while the structure remains semi-elastic at 5J, the 20J impact threshold generates critical “latent defects.” At this energy, significant shear damage and delamination were observed up to the 15th ply, despite negligible surface indentation. At 40J, the failure mechanism transitions to catastrophic stringer decohesion driven by flange stiffness mismatch. The research concludes that visual inspection is statistically unreliable for post-incident airworthiness assessment and recommends mandatory ultrasonic testing for any reported ground contact, alongside design optimisations to taper stringer flanges.