Production, Repairing and Testing of Hemp Reinforced Recycled HDPE Composites

This study explores the development and reparability of hemp fabric-reinforced recycled high-density polyethylene (r-HDPE) composites. Through hot press forming technique, laminates were fabricated and subjected to iterative testing cycles, including low-velocity impact and three-point bending tests. Post-damage repair was achieved via remoulding, assessing the evolution of mechanical properties over four repair cycles. Novelty lies in demonstrating the reparability and prolonged usability of these composites, highlighting their potential as a sustainable alternative to virgin HDPE. Results indicate enhanced impact resistance of hemp/HDPE compared to pure HDPE with an Fmax of 1500 N (45% higher than r-HDPE at 1034 N), while retaining structural integrity after multiple repairs. Advanced imagining techniques, such as CT scanning and phased array ultrasonic testing, provided detailed insights into damage mechanisms like matrix cracking and fibre debonding. While flexural strength decreased with repeated cycles, the composites maintained good performance under impact conditions especially considering impact energies lower than 10 J, at which repairing is possible without significant deterioration of impact properties, as the fibres are not significantly damaged. These findings position hemp/r-HDPE composites as viable, eco-friendly materials, aligning with circular economy principles by utilizing recycled polymers and vegetable fibres.