Dynamic axial crushing of combined composite aluminium tube: the role of both reinforcement and surface treatments

An experimental investigation was conducted to study both the crushing behavior and the practical adhesion of multi-material structures under dynamic compression conditions. Multi-material structures were made by wrapping a carbon/epoxy composite around the outside of an aluminium alloy circular tube. Prior to bonding, different surface treatments (i.e. chemicals etching, anodizing and degreasing) were used in order to improve the practical adhesion between the composite and the aluminium tube. Two geometries of aluminium alloy tubes, allowing a stable crushing mode, were tested. The specific energy absorption values obtained suggest that the influence of surface treatments of multi-material structures was not a significant contribution. For the thinner aluminium alloy tube, with or without the fiber reinforced plastic composites, a diamond mode is observed irrespective of the surface treatments. On the contrary, from a concertina mode obtained with the thicker aluminium tube without reinforcement, a diamond mode is observed with the reinforced one irrespective of the surface treatments. As the crushing mode has changed, the reinforcement applied onto the aluminium tube has decreased the capacities of the structures tested to absorb the energy. On the other hand, the reinforcement applied onto the thinner aluminium tube increased the specific energy absorption of a tube. To get a better understanding of the shock, a high-speed camera was used. It permits to differentiate the ability of a tube to dissipate the energy (i.e. characterized by the specific energy) and the ability of a tube to deform itself (i.e. characterized by the crush distance).