Preliminary Assessment of Untreated Encephalartos ituriensis Fiber as Reinforcement in PLA-Based Biocomposites

Abstract

This study explores the mechanical performance of poly(lactic acid) (PLA) biocomposites reinforced with natural fibers from Encephalartos ituriensis (E.I.), an underutilized tropical plant. Composite formulations containing 0, 5, 10, 15, and 20 wt% untreated E.I. fibers were melt-compounded using a twin-screw micro-compounder (Xplore MC 15 HT) and injection molded into ASTM D638-14 Type IV specimens for tensile testing. All tests were performed on a SHIMADZU AG-IC universal testing machine at 50 mm/min. The results showed that incorporating E.I. fibers at up to 10 wt% (0010) maintained tensile strength values relatively close to the neat PLA group (0000) (63.3 ± 0.3 MPa), with a moderate peak at 5% (0005) (59.6 ± 1.5 MPa). At 10% fiber loading, strength dropped slightly to 56.2 ± 1.6 MPa. Beyond this threshold, a progressive decline in tensile strength was observed, reaching 54.5 ± 0.6 MPa at 15% (0015) and 48.4 ± 4.8 MPa at 20% (0020) content. Conversely, the elastic modulus showed a steady increase with fiber addition, rising from 1227 ± 101 MPa for neat PLA to 1327 ± 44 MPa (5%), 1470 ± 17 MPa (10%), 1566 ± 39 MPa (15%), and peaking at 1660 ± 43 MPa for the 20% formulation, indicating improved stiffness with increasing reinforcement. Elongation at break decreased progressively from 7.34 ± 0.85% at 0% fiber content to 5.71 ± 0.40% at 5%, 4.92 ± 0.07% at 10%, 4.35 ± 0.02% at 15%, and dropped further to 3.61 ± 0.57% at 20%, suggesting a reduction in ductility with higher fiber loadings. These findings highlight the dual role of E.I. fibers: maintaining tensile strength at low loadings and enhancing modulus at higher ones. This supports their use as sustainable, high-modulus reinforcements in bio-based composites, with future work focusing on fiber treatment or hybrid designs.