Effect of alkali treatment on tensile strength of epoxy composite reinforced with coir fiber

This work is mainly focused on the comparative study of the effect of alkali treatment on the tensile strength of four variants of coir fiber-reinforced epoxy composites. The four variants, namely treated unidirectional fiber composite (TUC, 2% NaOH, 40 wt.% coir), untreated unidirectional fiber composite (UUC, 2% NaOH, 40 wt.% coir), treated woven fiber composite (TWC, 2% NaOH, 40 wt.% coir), and untreated woven fiber composite (UWC, 0% NaOH, 40 wt.% coir), were prepared using hand layup compression molding technique. Ten samples for each variant were selected for conducting ten replicated experiments for the tensile test. The combination with unidirectional geometry, 40 wt.% coir, and 2%NaOH (TUC) observed better tensile strength of 21.08 MPa when the average values were compared statistically with the other three variants. Also, between TWC and UWC, the difference between the average tensile strength is not significant. The untreated woven composite showed the least tensile property with 15.26 MPa. Comparison between all four variants of composites is shown using box-and-whiskers plot, and normal distribution curve. The tested specimen is then observed under scanning electron microscope (SEM) to understand the influence of the alkali treatment on the fiber, and the impact of the orientation of the fibers in the matrix. The SEM images reveal that roughened fiber with alkali treatment shows better bonding with the matrix hence improving the tensile strength of the composite.