Effect of tyre-derived rubber particle size on the mechanical properties of rubberised syntactic foam

This paper presents research findings on the influence of tyre-derived rubber particle size on the mechanical properties of rubberised syntactic foam manufactured through stir casting. The study examined how the rubber particle size affected the shear, in-plane compression, and through-thickness compression properties, as well as the flexural properties of sandwich composites with rubberised syntactic foam core. Rubber particles of various sizes (<150 µm, 150–250 µm, 250–425 µm, and >425 µm) were integrated into the syntactic foam at both low (9 wt%) and high (23 wt%) concentrations. Rubber particles measuring less than 150 µm, promoted agglomeration and increased void volume due to elevated viscosity, leading to a reduction in the mechanical properties of the rubberised foam. Conversely, larger rubber particles exceeding 425 µm reduced the mechanical properties of the syntactic foam due to debonding at the matrix/rubber interface. This study identified the optimal rubber particle size for achieving the highest mechanical properties in rubberised foam, which falls within the range of 150–425 µm. This research demonstrates the sustainable development of multifunctional composites from recovered waste tyres.