The energy-absorbing properties of composite tube-reinforced aluminum honeycomb

This paper investigates the energy-absorbing characteristics of a lightweight honeycomb core containing embedded carbon fibre reinforced plastic (CFRP) tubes. Initial tests are undertaken on the plain aluminum honeycomb material in order to characterize its specific energy absorption (SEA) capability and to identify the prevailing failure mechanisms. Tests are then conducted on honeycomb cores reinforced with increasing numbers of composite tubes in order to establish the influence of varying the density of the tubular array on the measured SEA. Finally, a series of drop-weight impact tests are conducted in order to characterize the dynamic response of these materials and assess their overall rate-sensitivity. Tests on the plain aluminum honeycomb cores resulted in the characteristic plastic wrinkling of the cell walls, yielding an average value of SEA of 14 kJ/kg. Embedding CFRP tubes into the honeycomb served to greatly enhance the energy-absorbing properties of the core, with quasi-static values of SEA reaching as high as 105 kJ/kg. An examination of the failed samples indicated that the previously-observed wrinkling mode of failure was largely absent, with the composite tubes being reduced to fine debris. Increasing the areal density of tubes in the honeycomb to relatively high values proved to be counterproductive, due to unwanted interactions between the individual tubes. Dynamic tests on the tube-reinforced honeycombs yielded SEA values that exceeded the quasi-static results with values reaching 112 kJ/kg for a moderately-reinforced core. Given the simplicity of the preparation process, it is believed that these lightweight structures represent an attractive cost-effective energy-absorbing material for use in dynamic applications. (c) 2017 The Authors. Published by Elsevier Ltd.