Lateral crushing of empty and polyurethane-foam filled natural flax fabric reinforced epoxy composite tubes

In this research, empty and polyurethane-foam filled natural flax fabric reinforced epoxy composite tubes were fabricated using a hand lay-up process. These circular flax/epoxy tubes were laterally crushed under quasi-static compression. The effects of tube thickness (2, 4 and 6 plies), tube inner diameter (64 and 86 mm) and the foam filler on the crushing characteristics and energy absorption capacity of these tubes were investigated. The progressive crushing of these tubes were analysed from photography. In addition, the energy absorption capacities of these empty and foam filled tubes were compared with the existing circular empty and/or foam filled tubes made of metallic materials (i.e. aluminium, brass, and titanium) and synthetic fibre reinforced composites (i.e. glass and carbon). The test results indicate that under lateral compression, the foam filled flax/epoxy tubes deformed showing a capability of spreading the deformation. The use of polyurethane-foam suppressed the fibre fracturing and eventually enhanced the energy absorption of the tubes during flattening process. The foam filled tubes with more fabric plies exhibited better crashworthiness compared to the empty tubes. The comparison with the existing tubes shows that the specific energy of natural flax/epoxy tube can be designed comparable to that of conventional aluminium tube and the glass/carbon composite tube as energy absorbers. It also was found that the specific energy of the empty and foam filled flax/epoxy tubes in lateral crushing were significantly lower than those in axial crushing. (C) 2014 Elsevier Ltd. All rights reserved.