The shear response of lightweight corrugated core structures

A combination of experimental, analytical and numerical techniques is used to characterise the shear response of lightweight corrugations based on glass fibre and carbon fibre reinforced epoxy resins. The corrugations were manufactured via a compression moulding procedure in which composite prepregs are cured between two serrated mould halves. The properties of the composite corrugations are compared with those offered by a similar aluminium system. Subsequent mechanical testing was undertaken using an Arcan rig capable of generating a range of loading conditions between pure shear and pure compression. As a result of difficulties in accurately measuring the displacement of the cores under mixed-loading conditions, an analytical model was used to predict the stiffness characteristics of the cores as a function of loading angle. The accuracy of the model was assessed using a finite element analysis. The final part of this investigation focused on fitting the measured values of maximum strength to an appropriate failure criterion. An examination of the corrugated structures during combined compression-shear loading indicated that the composite samples failed as a result of buckling in the strands and in certain cases, delamination between the composite plies. Both the analytical model and the finite element analysis indicated that the stiffness of composite and aluminium cores did not vary significantly with loading angle. An analysis of the strength characteristics of the corrugated cores showed that the aluminium corrugations could be accurately represented using a two-dimensional quadratic failure criterion. In contrast, due to the initiation of delamination within the composite struts, an additional component in the failure criterion was required to accurately capture the response of the composite corrugations.