GFRP-Polyurethane Sandwich Panels under Reversed Bending Fatigue

Sandwich panels composed of lightweight polyurethane core and GFRP skins have a great potential for a variety of applications. Some of the promising applications include cladding of buildings, in which the lightweight panels are used to provide the building envelope in terms of insulation and protection from the elements, and in lightweight decking applications of pedestrian bridges or platforms. In cladding applications, although the panels are not of the load-bearing type, they are subjected to a strong wind pressure or suction. In this case the panels are repeatedly loaded in cyclic bending, which may cause fatigue problems. This study investigates sandwich panels in four point reversed cyclic bending. The panels were exposed to various stress levels and for each level; the number of cycles to failure was established. Stiffness degradation characteristics were also measured at various stages of loading. It was shown that at a cyclic load of +/- 30% of the ultimate monotonic flexural strength, the panels were able to sustain over 2 million cycles.