Prediction of the first failure energy of circular carbon fibre reinforced plastic plates loaded at the centre

This work was devoted to the prediction of the elastic energy stored at first failure in a circular composite plate statically loaded at the centre. To describe the load–deflection curve, a previous model was further developed, to explicitly account for the tup diameter. The first failure load was calculated through a simple formula, available in the literature, which was suitably varied. An original expression was derived for the energy at first failure. The experimental tests were carried out on carbon fibre reinforced plastic laminates of various thicknesses, which were simply supported at the periphery and loaded using different support and indentor diameters. The results obtained show that the elastic model, which takes into account the non-linearity deriving from large displacements and local indentation, is very accurate in shaping the load–deflection curve up to the first failure point. In general, also the predicted load and energy at first failure are in good agreement with the corresponding measured values. Both theory and experiments demonstrate that the critical load is independent of the support diameter, whereas it increases with increasing the plate thickness and the indentor diameter. When the support diameter and thickness increase, the energy at first failure increases as well. A particular condition, resulting in the failure of the force model, is achieved when the curvature of the plate at first failure is considerable. In this case, critical forces notably higher than expected from theory are measured. A possible explanation for this behaviour is given. 2003 Elsevier Science Ltd. All rights reserved.