Mechanical Behavior of Sandwich Panels with Hybrid PU Foam Core

The traditional composite sandwich structures have disadvantages of low shear modulus and large deformation when used in civil engineering applications. To overcome these problems, this paper proposed a novel composite sandwich panel with upper and lower GFRP skins and a hybrid polyurethane (PU) foam core (GHP panels). The hybrid core is composed of different densities (150, 250, and 350 kg/m³) of the foam core which is divided functionally by horizontal GFRP ribs. The hard core is placed in the compression area to resist compressive strength and improve the stiffness of the composite sandwich structure, while the soft core is placed in the tension area. Six GHP panels were tested loaded in 4-point bending to study the effect of horizontal ribs and hybrid core configurations on the stiffness, strength, and failure modes of GHP panels. Experimental results show that compared to the control panel, a maximum of 54.6% and 50% increase in the strength and bending stiffness can be achieved, respectively. GHP panels with the hybrid PU foam core show obvious secondary stiffness. Finally, analytical methods were proposed to predict the initial stiffness and peak load of the GHP panels, and the results agree well with experimental results.

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