This study aimed to investigate the mechanical properties of prosthetic sockets reinforced with fumigated King Pineapple Rob X (KPRF) fibers and microcrystalline cellulose (MCC). The KPRF fibers were extracted from King Pineapple Rob X leaves using a manual retting method and subsequently subjected to fumigation treatments in a chimney for 0, 5, 10, and 15 hours, utilizing coconut fibers and shells as the combustion source. The composite prosthetic sockets were fabricated using an unsaturated polyester (UPR) matrix reinforced with the treated fibers and MCC. To ensure a homogenous distribution, the matrix and MCC were blended using a magnetic stirrer at 250 rpm and 40°C for 30 minutes. Post-fabrication, the composites were oven-dried at 60°C for 6 hours prior to specimen preparation. The analytical results from X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA) revealed an increase in the crystallinity index and enhanced thermal stability of the fibers following treatment. Scanning Electron Microscopy (SEM) observations confirmed that fumigation effectively purified the fiber surfaces by removing non-cellulosic impurities. Mechanical testing indicated that the FM 10 (10-hour fumigation) variant achieved the highest tensile strength, while the untreated (UT) specimens exhibited the lowest performance. Furthermore, water absorption tests demonstrated that untreated fibers had the highest moisture uptake, whereas fumigated fibers showed improved hydrophobicity. Structural evaluation according to ISO 10328 standards yielded a peak compressive strength of 38,866.60 N for the 10-hour fumigation group. Finally, Finite Element Analysis (FEA) validated the structural integrity of the socket, confirming its suitability for physiological patient loading.
