The effect of oil palm empty fruit bunch (Elaeis guineensis Jacq.) fiber addition at various volume fractions on the compressive strength of flowable composite resin

Oil palm empty fruit bunch (OPEFB) fibers have emerged as a promising natural alternative to synthetic fibers due to their mechanical strength and biocompatibility, although research on their use as a reinforcing in composite resin remains limited. This study aimed to evaluate the effect of OPEFB fiber incorporation on the compressive strength of flowable composite resin. A true experimental design with a post-test-only control group was employed. The OPEFB fibers underwent chemical and double silane treatments and were randomly oriented prior to incorporation. Fifteen cylindrical specimens (6 mm × 12 mm) were allocated into three groups based on fiber volume fraction (0%, 1%, and 1.5%). Compressive strength was tested using a universal testing machine following ASTM D-695 standards. Data were analyzed using one-way ANOVA (p < 0.05) followed by a post-hoc Least Significant Difference (LSD) test. The mean compressive strength of flowable composite resins at 0%, 1%, and 1.5% OPEFB fiber volume fractions were 261.99 ± 17.64, 301.20 ± 19.26, 368.52 ± 14.90 MPa. One-way ANOVA test showed that the mean compressive strength in the three groups was significantly different (p < 0.05). The post-hoc LSD test showed significant differences (p < 0.05) among all groups. This study concluded that the incorporation of OPEFB fiber can enhance the compressive strength of flowable composite resin, with the highest reinforcement observed at the 1.5% OPEFB fiber volume fraction.