Modelling the impact behaviour of sandwich structures with folded composite cores

The European aircraft industry has strong interest in novel structural concepts for future aircraft fuselage with lower fabrication costs and high performance. A critical safety issue for the design of aircraft structure is vulnerability and damage tolerance due to foreign object impact. This paper focuses on the improvement of modelling techniques for foldcore sandwich structures with composite skins under low velocity impact. A new modelling approach for the foldcore cell wall material – aramid paper – is presented, which considers the aramid papers inhomogeneous nature in the thickness direction. In combination with in-ply continuum damage mechanics and a cohesive delamination interface for the modelling of the composite surface skin the proposed modelling approach is used to reproduce drop tower impact tests performed at various impact velocities. Results and interpretation of the numerical and experimental work are presented. The strengths and weaknesses of the presented modelling approach are discussed and evaluated.