from the conferences organized by TANGER Ltd.
Polyurethane (PU) modelling boards and foams are widely used for manufacturing prototypes, models, and moulds; however, CNC machining generates substantial amounts of fine chips and dust that are typically downcycled or landfilled. This paper presents a mechanically straightforward upcycling route in which PU machining chips are milled, sieved, and re-used as a loose particulate core in carbon/epoxy sandwich composites. The sandwich panels were manufactured by hand lay-up with vacuum assistance or by vacuum infusion to keep the process low-tech and readily transferable to prototyping practice. Flexural behaviour was assessed by three-point bending in accordance with ISO 178, and the results were interpreted using load-deflection responses complemented by macroscopic inspection and fractographic evaluation of failed specimens. A characteristic sandwich response was observed, with damage initiation in the core (shear and local densification) followed by a transfer of load being carried predominantly by the facesheets. The discussion shows that mechanical stability is particularly sensitive to the homogeneity of the particulate layer, local porosity, and the degree of matrix infiltration, which together govern the core shear capacity and the adhesion at the facesheet-core interface. The proposed approach demonstrates the material potential of recycled PU chips for lightweight composite panels and identifies key optimisation directions to improve process repeatability and scalability in model and mould manufacturing. The concept leverages the fact that the flexural stiffness and strength of a sandwich are primarily determined by the facesheets, whereas the core обеспечивает shear transfer and stabilisation. Overall, the study contributes to circular-economy strategies for modelling materials and highlights practical pathways for value-added utilisation of waste PU fractions.
Keywords: polyurethane recycling; CNC machining waste; sandwich composite; carbon fibre; mechanical testing© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.