Flexural behaviour of GFRP sandwich panels with eco-friendly PET foam core for the rehabilitation of building floors

This paper presents an experimental investigation about the flexural behaviour of different types of GFRP composite sandwich panels, focusing on the evaluation of different variables, such as the use of different core materials (polyurethane (PUR) vs. polyethylene terephthalate (PET) foams) and various GFRP web configurations, including homogeneous-core and web-core panels. Experimental tests were conducted using a four-point bending setup, and the obtained results were analysed in terms of load-deflection behaviour, bending stiffness, and failure modes. Overall, the homogeneous PET sandwich panels exhibited higher ultimate loads compared to the PUR specimen; this stems from the higher shear strength of the PET foam compared to the PUR foam. Moreover, the longitudinal web reinforcement significantly increased the load-bearing capacity of the web-core sandwich panels compared to the homogeneous-core specimens (from 4.3 to 9.3 times). Concerning the failure modes, the homogenous-core sandwich panels failed in a brittle manner due to (i) shear failure of the foam cores and (ii) delamination failure at the core-GFRP interface whereas the collapse of the web-core sandwich panels was triggered by crushing of the top face sheet, followed by transverse compressive failure of the webs.