Axial response of flax fibre reinforced polymer-skinned tubes with lightweight foam cores and bioresin blend

The response of non-slender flax fibre reinforced polymer (FFRP)-skinned foam filled tubes under axial compression was investigated using 39 specimens. Different cross-ply fibre arrangements and foam densities (33-65 kg/m(3)) were tested; the responses were compared to hollow FFRP tubes and Glass-FRP (GFRP) skinned tubes. Although axial behaviour was not significantly affected by changing foam density, hollow tubes were weaker than foam filled sections. This suggests that low density foam is effective at preventing premature failure. FFRP-skinned tubes with a skin thickness of 6.4 mm behaved similarly to GFRP-skinned tubes with a skin thickness of 3.4 mm in terms of strength and stiffness but were considerably better at absorbing energy. Specific strength and stiffness were highest with the lightest foam. The best performing FFRP-skinned tubes had specific strengths about 75% that of GFRP-skinned tubes with similar dimensions and equivalent foam cores.