Experimental investigation of the collapse modes and the main crushing characteristics of composite sandwich panels subjected to flexural loading

The flexural properties, collapse modes and crushing characteristics of various types of composite sandwich panels - that were candidate materials for the manufacture of the front-end bumper of transportation vehicles - were investigated in a series of three-point bending tests that were performed in accordance with the American Society for Testing and Materials International Standard D790. The tested hybrid composites were constructed trying four types of polymer foam core (more specifically polymethacrylimide foam, cross-linked and linear polyvinyl chloride foam and polyurethane foam) and two types of fibreglass reinforced polyester faceplate laminates made of glass fibre reinforcements impregnated in modified acrylic resin, in eight different material combinations. Two modes of collapse were recorded in the series of flexural tests: the first was foam core shear failure and the second was local indentation collapse mode. The influence of the most important material properties of the faceplate laminates and foam core and the sandwich construction geometry on the flexural response and the crushing characteristics of the tested sandwich panels such as the peak load, crash energy absorption and collapse modes is extensively analysed. Particular attention is paid to the analysis of the mechanics of progressive deformation and crumpling of the sandwich panels in each of the collapse modes emphasising the mechanisms related to the crash energy absorption during the bending of the sandwich panels.