Sustainable Boatbuilding: Evaluating the Feasibility of Recycled HDPE as a Structural Material

The boatbuilding industry is increasingly shifting toward environmentally sustainable materials. High-Density Polyethylene (HDPE) has become a highly viable alternative material because of its outstanding chemical and impact resistance, as well as its low-carbon manufacturing process. This makes it a practical substitute for traditional materials such as wood and fiberglass-reinforced plastic for constructing small vessels. However, the substantial generation of HDPE waste poses a significant challenge in maritime manufacturing. In response, this study presents a solution for the plastic waste produced during boatbuilding by recycling HDPE sourced from the Non-Metal Workshop at the Shipbuilding Institute of Polytechnic Surabaya (PPNS) and evaluating its suitability for use as a manhole cover. The compliance of recycled HDPE (r-HDPE) as a structural material was assessed based on the BKI (Biro Klasifikasi Indonesia) Standards for Thermoplastic Vessels, Volume 2, 2023 Edition. The mechanical testing of r-HDPE showed a tensile strength of 24.50 MPa and a flexural strength of 41.93 MPa. Finite Element Analysis using ANSYS showed that increasing the cover thickness from 6.5 mm to 12.5 mm significantly reduced deformation and stress, resulting in a safety factor of 8.29 under a maximum load of 1470 N. Therefore, 12.5 mm thick r-HDPE is structurally viable and supports sustainable shipbuilding by reducing waste.