Effects of material non-linearity on the structural performance of sandwich beams made of recycled PET foam core and PET fiber composite facings: Experimental and analytical studies

Abstract

This paper presents the results of experimental and analytical studies on sandwich beams subjected to three-point bending beyond their limit of proportionality. The sandwich beams were composed of polyethylene terephthalate (PET) fiber-reinforced polymer (FRP) composite facings and recycled PET (R-PET) foam core made from post-consumer plastic bottles. The study tested three R-PET core densities (70, 80, and 100 kg/m3) and compared the results to a control group with 100 kg/m3 core density and glass FRP facings. The beam geometry and testing set-up were consistent throughout the study, with 12 beams tested in total. The results showed that all specimens exhibited non-linear load–deflection behavior, resulting in developing a non-linear analytical model using decreasing secant elastic and shear moduli under increasing loads. The proposed model was validated, and a parametric analysis was performed to evaluate its mechanical performance under different conditions, including variations in span length and the thickness of the core and facing components. Additionally, the study created a novel failure mode map to predict the failure mechanism of the sandwich panels based on core density and the PET FRP facing thickness to span length ratio, considering the non-linear behavior of both components. As a result, this study provides valuable insights into using recycled materials in construction, contributing to reducing plastic waste and mitigating environmental impact.