Deformation and energy absorption of composite egg-box panels

Static compressive tests of composite egg-box panels, whose stacking sequences and number of plies were controlled, were carried out to investigate their deformation behaviour and energy absorption capacity. Silicon rubber moulds were first moulded from an aluminium egg-box panel template. These moulds were in turn used to fabricate composite specimens. Two fabric prepregs, carbon/epoxy plain weave fabric and glass/epoxy 4-harness satin weave were draped over the rubber mould with various stacking angles. The specimens were cured in an autoclave using vacuum bag degassing moulding and an appropriate cure cycle. The nominal stress–strain relations of the specimens were compared and multiply-interrupted compressive tests were used to identify fracture initiation and development. The energy absorption per unit mass of composite egg-box panels were compared with that of an aluminium egg-box panel. From the test results it was concluded that the compressive behaviour of the composite structure is affected by the local stacking sequence of the fabrics and by shear deformation during initial lay-up and draping. By considering the stress–stain behaviour, energy absorption and material cost, the optimal material and draping condition were proposed for a composite egg-box panel.