The energy-absorbing properties of internally reinforced composite-metal cylinders with various diameter-to-thickness ratios

In order to enhance the energy-absorbing behaviour of both new and existing metallic structures, metal cylinders are reinforced by inserting an internal composite cylinder. Initially, the energy-absorbing characteristics of the individual composite and metal rings with a large variety of the diameter-to-thickness ratios is assessed separately through a series of compression crushing tests, prior to testing the metal-composite hybrids. It was found that the values of specific energy absorption for the composite rings varied from 48.1 to 93.3 kJ/kg and those for the aluminium systems from approximately 20.9 to 70.1 kJ/kg. Here, the smaller aluminium rings failed in a localised buckling mode, whereas some of the larger rings failed in a low-energy fracture mode. In contrast, the small diameter composite samples failed in a combination of splaying and fragmentation modes, reducing the rings to small fragments and fine debris. The larger diameter rings failed in a delamination/splitting mode involving lower levels of energy absorption. However, the specific energy absorption values for the aluminium-composite structures were higher than the individual aluminium rings. The percentage increase in specific energy absorption ranged from 20 to 70% as the outer ring diameter was increased from approximately 19 to 66 mm. This evidence suggests that composite cylinders and tubing can be inserted into new or existing metallic components in order to greatly enhance their energy-absorbing behaviour.