Flexural Strength Response of Coconut Coir Fiber-Reinforced Epoxy Composites Across Titanium Dioxide Contents
DOI:
https://doi.org/10.59261/jequi.v8i5.485Keywords:
Coconut Coir, Epoxy, Flexural Strength, Three-Point Bending, Titanium DioxideAbstract
Background: Flexural performance is a critical design property of coconut coir fiber-reinforced epoxy composites; however, evidence regarding TiO₂-filled systems across multiple filler contents remains limited.
Objective: This study examined the flexural strength response of composites containing 0, 1, 3, 5, and 7 wt.% TiO₂ to determine whether any filled formulation exhibited flexural strength recovery toward that of the unfilled control.
Methods: Composites were fabricated using an epoxy-to-hardener ratio of 60:40, a matrix-to-fiber ratio of 75:25, and untreated, randomly oriented coir fibers approximately 50 mm long, using the hand lay-up method. Flexural testing was conducted in accordance with ASTM D790-25, with three specimens tested per formulation. Scanning electron microscopy (SEM) was used to examine the fracture surfaces. One-way analysis of variance (ANOVA), Tukey’s honestly significant difference (HSD) test, Levene’s test, Welch’s ANOVA, and the Kruskal–Wallis test were employed to evaluate the results and assess the sensitivity of the findings to the limited replication.
Results: The mean flexural strengths of the 0, 1, 3, 5, and 7 wt.% TiO₂ formulations were 31.61 ± 3.75, 22.59 ± 0.62, 28.78 ± 1.42, 28.05 ± 0.87, and 30.66 ± 4.34 MPa, respectively. One-way ANOVA indicated statistically significant differences among the formulations (image). Tukey’s HSD test identified statistically significant differences between the 0 and 1 wt.% formulations and between the 1 and 7 wt.% formulations. No TiO₂-filled formulation exhibited a statistically significant increase in flexural strength relative to the unfilled control. Sensitivity analyses highlighted the uncertainty associated with the small sample size, while SEM observations revealed interfacial debonding, fiber pull-out, interfacial gaps, fibrillation, and voids.
Conclusion: The 7 wt.% TiO₂ formulation exhibited the closest numerical recovery in flexural strength toward the unfilled control and therefore represents a candidate for further investigation. These findings should be interpreted cautiously because of the limited replication, incomplete metadata, and qualitative nature of the SEM observations.
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