Compression Molding of Rice Husk Reinforced Polyurethane Composite Using a Hydraulic Press Tool

Abstract

The increasing demand for sustainable engineering materials has driven growing interest in natural fiber-reinforced polymer composites as alternatives to synthetic fiber-based materials. Rice husk, an abundantly available agricultural by-product in Indonesia, possesses considerable potential as a natural fiber reinforcement due to its cellulose content of approximately 35-40% and its widespread availability at low cost. However, the fabrication of standardized composite specimens for mechanical characterization requires a reliable and purpose-built pressing tool that is currently lacking at the laboratory scale. This study presents the design, fabrication, structural analysis, and experimental validation of a hydraulic press mold system intended for producing rice husk fiber-reinforced polyurethane composite panels at a laboratory scale. The mold frame was constructed from St.42 carbon steel using a built-up assembly method, incorporating a 20-ton hydraulic jack as the pressing mechanism and a mold cavity of 250×250 mm. Structural integrity was verified through analytical calculation and Finite Element Analysis simulation, yielding a safety factor of 15 and a maximum displacement of 6.39 mm under the full design load, confirming the reliability of the tool under operating conditions. Rice husk fiber cut to three size variations of 20×10 mm, 30×10 mm, and 40×10 mm was combined with polyurethane resin as the matrix, and a total of 20 composite panels measuring 200×200 mm with a thickness of 3.67-4.44 mm were successfully produced. Tensile and flexural test specimens were prepared in accordance with ASTM D638-02 and ASTM D790-03 standards, respectively. The highest tensile strength of 53.6 MPa and flexural strength of 22.66 MPa were recorded for composites reinforced with 40×10 mm fiber at a fiber volume fraction of 5%. The fabricated mold system demonstrated consistent dimensional output and repeatable fabrication performance, confirming its suitability as a cost-effective tool for laboratory-scale natural fiber composite research.