Sustainable Macadamia Nutshell-Based Particulate Composites: Mechanical Performance and Application Potential in Structural Materials

Abstract

Growing environmental concerns and the global shift toward circular economy practices have accelerated research into bio-composites derived from agricultural by-products. This study presents an initial systematic investigation of ground macadamia nutshell (MNS)-based particulate composites reinforced with epoxy and vinyl ester resins. The effects of filler content (5-30 wt.%) on mechanical performance were evaluated through compressive, tensile, flexural and SEM analyses. Results reveal that composites containing 10-20 wt.% MNS exhibit optimal strength-to-weight ratios, with flexural strength improvements of up to 15% compared to neat resins. Comparative analysis highlights the unique advantages of macadamia nutshells, high density, hardness, and availability as agro-waste, over other natural fillers. These findings demonstrate that MNS composites are not only environmentally sustainable but also mechanically competitive with conventional timber and synthetic composites, offering scalable potential for eco-construction, green building, and structural applications.