Sandwich structures with textile-reinforced composite foldcores under impact loads

The mechanical behaviour of composite sandwich structures with textile-reinforced composite foldcores, which are produced by folding prepreg sheets to three-dimensional zigzag structures, is evaluated under compression, shear and impact loads. While foldcores made of woven aramid fibres are characterised by a rather ductile behaviour, carbon foldcores with their brittle nature absorb energy by crushing, showing extremely high weight-specific stiffness and strength properties. The impact damage under low and high velocity impact loads tends to be very localised. In addition to regular single-core sandwich structures, a dual-core configuration with two foldcores is also investigated, showing the potential of a two-phase energy absorption behaviour. In addition to experimental testing, finite element models for impact simulations with LS-DYNA have been developed. Despite the high degree of complexity of the models due to the various skin and core failure modes that have to be covered, the results correlate well with test data, allowing for efficient parameter studies or detailed evaluations of damage patterns and energy absorption mechanisms.