Flexural behaviour of composite sandwiches for structural applications

Abstract

In this paper, structural composite sandwich was investigated under 3 and 4-point static bending tests in the flatwise and edgewise positions to analyse the contribution of the skins in the load carrying capacity and failure mode under flexure. The skins of the composite sandwich are made up of tri-axis E-glass fibres infused with epoxy resin and the core material of fly ash with low density polystyrene beads. Structural composite sandwich with span lengths of 200, 400 and 800 mm was tested until final failure. Analytical calculation of the load capacity and deflection of the composite sandwich was conducted and compared with the experimental results. Preliminary investigation showed that the percentage contribution of the skins in the flexural capacity of composite sandwich tested in the flatwise position is higher than that of the edgewise position. However, the specimen tested in the edgewise position failed at a higher load and exhibited a higher flexural stiffness. The specimens tested in the flatwise position failed due to core shear failure followed by delamination between the skin and the core. On the other hand, the specimens tested in the edgewise position failed in a brittle manner due to the simultaneous shear failure of the skin and the core. The results also showed that the flexural behaviour of the structural sandwich can be predicted analytically using the simple beam theory. For structural composite sandwich, the combined contribution of the skin and the core in carrying the load should considered to efficiently design a composite sandwich structure.