Behaviour of fibre-reinforced honeycomb core under low velocity impact loading

In this study, the behaviour of two different types of cores, short flax fibre reinforced and continuous flax fibre reinforced polymeric cores, is investigated under low velocity out-of-plane impact loading. The fibre-reinforced corrugations were manufactured by using matched-die compression moulding and the resulting cells were bonded using ultrasonic methods to form recyclable honeycomb cores. A drop weight impact tester, Imatek IM10T-20 ITS, capable of producing velocities up to 20 m/s coupled with a high-speed camera (Phantom), was used to capture video images of the impact. The displacement of the impactor was recorded with a digital displacement transducer and the force was recorded with a digital force transducer. The effects of reinforced material type, the core height and the presence of face sheets including all their interactions on the energy absorption are determined by using statistical analysis based on the Taguchi method. The impact results reveal a better energy absorption when honeycombs with cell walls reinforced with continuous fibres are used; the presence of face-sheets plays an important role in energy absorption only at lower core height. This is confirmed by the results of the statistical analysis revealing antagonistic interaction between the core height and face sheets.