Failure mode maps for circular composites sandwich plates under bending

Competing failure modes are investigated for circular sandwich plates comprising quasi-isotropic E-glass/ epoxy composite faceplates (with [-60/0/60](ns), configuration) and polyvinyl chloride (PVC) foam core under bending. Clamped sandwich plates are loaded using flat-ended punch at the center of the plate. Three competing failure modes, viz., core indentation, core shear and face failure/microbuckling, are considered. Analytical estimates for elastic response (stiffness) and initial failure load are proposed, and these are verified by experimental measurements and finite element (FE) predictions. Good agreement (with in +/- 20%) is observed among analytical estimates, experimental measurements and FE predictions. Analytical estimates for the failure modes are used to plot the failure mode map in non-dimensional plate radius versus faceplate thickness plane for a given material system. The failure mode map thus constructed is assessed by considering a few sandwich plate geometries. Normalized sandwich mass and failure load contours are superimposed onto the failure mode map to identify the locus of minimum weight design by numerical search. Effect of geometrical parameters of the sandwich plate on failure load and mode is also investigated. (C) 2014 Elsevier Ltd. All rights reserved.