Manufacturing, thermoforming, and recycling of glass fiber/ PET/ PET foam sandwich composites: DOE analysis of recycled materials

Abstract This article presents efficient methods to manufacture, thermoform, and recycle sandwich composites consisting of glass fiber (GF)/polyethylene terephthalate (PET) composite skins and a PET foam core. Sandwich composite panels were manufactured using a hot press, which involved heating and pressing from the upper and lower platens inducing thermal fusion between the skin and the foam core. The formability of the sandwich composite panels using a hot press and a pocket‐shaped mold was simulated to determine the forming conditions. And the formability of the sandwich composite panels was tested using the simulation results. Recycling of the sandwich composite panels was achieved using recycling molds to perform heat compression. The excess PET was separated from the GF/PET composite and re‐impregnated with the remaining GF and PET. As a result of recycling, recycled PET and PET/GF composite were obtained. Design of experiments (DOE) analysis was conducted to analyze the recycled properties and to identify which factors affected these properties. These results were re‐plotted according to DOE priority ranking to identify the changes in the properties of the recycled materials per factor. Compared to the original properties, the mechanical and thermal properties including modulus, ultimate tensile strength, melting temperature and crystalline temperature were ~ 95 and ~ 99% preserved. These findings are expected to contribute towards the development of recyclable sandwich composite panels with reduced mass production cost, which are easily formed, used and recycled.