SUSTAINABLE SANDWICH PANELS MADE FROM REUSED BOTTLE CAPS, GALVANISED STEEL FACINGS AND RENEWABLE ADHESIVES
Sandwich panels, mechanical properties, plastic wastes
Growing environmental concerns associated with the disposal of polymers and petrochemical-based materials have driven industries to adopt more sustainable alternatives. This study compares the mechanical performance of two distinct bio-based castor oil-based adhesives and a commercial epoxy system. The adhesives are applied to lightweight sandwich panels manufactured with galvanised steel facings and a core consisting of upcycled bottle caps. A statistical design is employed to identify the effects of two key factors on adhesive performance and the structural integrity of the panels. First, the galvanised steel sheets are sanded to achieve different levels of surface roughness, and the effect of surface roughness on adhesive performance is quantified through single-lap shear tests. Second, the effect of small gaps formed by the hexagonal arrangement of the bottle caps within the core is investigated. Three-point bending tests are conducted to compare six key panel properties: flexural modulus, flexural strength, maximum load, modulus of resilience, face stress, and core shear modulus. The results indicate that the presence of gaps within the bottle-cap core consistently reduces the mechanical properties of all the panels tested. However, one of the castor oil-based bio-based adhesives exhibits promising mechanical performance compared with the commercial epoxy adhesive.