Mechanical Characterisation of Aluminium-Faced Sandwich Panels Incorporating Upcycled PVC Ring Cores

Abstract In the construction industry, PVC pipe off-cuts constitute a significant source of high-quality waste that is frequently disposed of in landfill. This study develops and evaluates the physical and flexural performance of environmentally sustainable aluminium-faced sandwich panels incorporating upcycled PVC pipe off-cuts as a circular honeycomb core. The core is manufactured by arranging PVC rings in cubic and orthotropic configurations, with or without mechanical interlocking joints, and bonding them to structural aluminium face sheets using an epoxy adhesive. A factorial Design of Experiments (DoE), combined with Analysis of Variance (ANOVA) and Student’s t-test, is employed to quantify the effects of ring diameter (20 mm and 32 mm), packing geometry (cubic and orthotropic), and mechanical interlocking on the equivalent density, flexural strength, and flexural modulus of the sandwich panels under three-point bending. The results indicate that the orthotropic packing geometry increases the flexural strength by 3.6% compared with the cubic configuration (p < 0.05). In addition, reducing the ring diameter to 20 mm increases the flexural modulus by 4.7%, while pristine core assemblies (without mechanical interlocking) exhibit a flexural modulus 2.7% higher than that of interlocked cores (p < 0.05). Overall, the proposed sandwich structures demonstrate that upcycled PVC pipe off-cuts provide a technically viable and sustainable alternative to conventional core materials for lightweight structural sandwich applications, contributing to both waste valorisation and circular economy strategies.