Crashworthiness characteristics of composite cylindrical energy absorbers filled with honeycomb and foam under quasi-static load: experimental and analytical study

In this study, the crashworthiness characteristics of four cases including cylindrical hollow composite tubes, aluminum honeycomb-filled tubes, polyurethane foam-filled tubes, and polyurethane foam/aluminum honeycomb-filled cylindrical composite are experimentally investigated. The impact of honeycomb, polyurethane foam, combined polyurethane foam with honeycomb filling, and diameter and thickness of wall of cylindrical composites are also investigated. Then, the deformation mode, peak crushing force, mean crushing force (MCF), energy absorption (EA), and specific energy absorption of these composites possessing different structures are also explored. Furthermore, an analytical model for the crushing behavior of the cylindrical composite shell filled with foam and honeycomb materials under quasi-static load is provided. The analytical model which draws on the energy method is used to predict the MCF and crushing length during the collapse process. For this purpose, the diverse phenomena including shell bending, petal formation, circumferential delamination, friction, collapse of honeycomb cell walls, and deformation of foam are considered to determine the total internal energy relations during the crash process. These relations are used to make predictions on mean loads and total displacements during the collapse. The obtained results reveal a relatively good agreement between the analytical and experimental findings. The results showed that all novel cylindrical composite tubes filled with both polyurethane foam and aluminum honeycomb, in addition to increasing energy absorption compared to their counterparts, deform only in the stable mode of collapse (Mode I), which is a very important predictable deformation in terms of design.