Performance enhancement of recycled HDPE reinforced with granite micro particles for sustainable low-impact body armor systems

Composite materials with a polymer matrix are extensively utilized in body armor systems, with particular emphasis on the matrix phase. This study optimizes the performance of recycled high-density polyethylene (HDPE) by reinforcing it with waste granite micro-particles at varying weight percentages (5 wt%, 10 wt%, and 15 wt%) and mixing times (2, 4, and 6 min) using a mechanical stirrer to achieve the optimal balance of impact strength, rigidity, durability, and processing efficiency for protective applications. The granite powder, a waste byproduct of marble and granite industries, was incorporated as a filler to improve the mechanical properties of recycled HDPE while addressing environmental challenges posed by both plastic waste and industrial byproducts. The results showed significant improvements: low strain rate impact strength increased by 18.40% at 5 wt% granite content and a mixing time of 6 min, hardness improved by 52.05% at 15 wt% granite content and a mixing time of 6 min, and quasi-static compressive strength increased by 32.59% under the same conditions. Water absorption increased slightly with higher granite content, with the lowest absorption of 0.40% observed at 5 wt% granite content and a mixing time of 2 min. Multi-response optimization identified the optimal parameters as 9.47% granite weight fraction and a 6-min mixing time, achieving a balance between key performance metrics. By utilizing recycled HDPE and waste granite particles, this study provides an eco-friendly, cost-effective approach to creating high-performance materials for low-impact body armor systems and other protective applications, contributing to waste reduction and sustainable development.