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Through-thickness polymer pin-reinforced foam core sandwich (FCS) panels are new type of composite sandwich structure as the foam core of this structure was reinforced with cylindrical polymer pins, which also rigidly connect the face sheets. These sandwich panels are made of glass fiber-reinforced polyester face sheets and closed-cell polyurethane foam core with cylindrical polymer pins produced during fabrication process. The indentation and compression behavior of these sandwich panels were compared with common traditional sandwich panel, and it has been found that by reinforcing the foam core with cylindrical polymer pins, the indentation strength, energy absorption, and compression strength of the sandwich panels were improved significantly. The effect of diameter of polymer pins on indentation and compression behavior of both sandwich panels was studied and results showed that the diameter of polymer pins had a large influence on the compression and indentation behavior of through-thickness polymer pin-reinforced FCS panel, and the effect of adding polymer pins to FCS panel on indentation behavior is similar to the effect of increasing the thickness of face sheet. The effect of strain rate on indentation behavior of FCS panel and through-thickness polymer pin-reinforced FCS panel were studied, and results showed that both types of composite sandwich panels are strain rate dependent structure as by increasing strain rate, the indentation properties and energy absorption properties of these structures are increased. POLYM. COMPOS., 37:612-619, 2016.

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Fibre reinforced polymer (FRP) plates subject to quasi-static indentation loading were studied. The plates were fabricated from three layers of chopped strand mat glass fibre and polyester resin using vacuum infusion process. Indentation tests were conducted on the plates with loading rates of 1 mm/min, 10 mm/min, 100 mm/min and 500 mm/min using a hemispherical tip indenter with diameter 12.5 mm. The plates were clamped in a square fixture with an unsupported space of 100 mm × 100 mm. The loads and deflections at the indented location were measured to give energy absorption-deflection curves. The results showed that the loading rate has a large effect on the indentation behaviour and energy absorbed.

The present study focuses on the flexural and the indentation behaviour of foam core sandwich panel subject to three point bending and indentation loading at different loading rates. The load-deflection, stress-deflection responses and energy absorption properties of foam core sandwich panel are determined experimentally. The foam core sandwich panel was fabricated using vacuum infusion process. The sandwich structure consists of chopped strand mat fibreglass skins and polyurethane foam core. The flexural and the indentation tests were conducted using Instron Universal Testing machine. It was found that loading rate influences the flexural and the indentation behaviours of foam core sandwich panel. By increasing the loading rate, the stiffness, strength and energy absorption of flexural and indentation of these structures were increased.