The effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites

The present paper investigates the effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites. Treatments including alkalization, acetylation, cyanoethylation, the use of silane coupling agent, and heating were carried out to modify the fiber surface and its internal structure. As indicated by infrared spectroscopy, X-ray diffraction and tensile tests, variations in composition, structure, dimensions, morphology and mechanical properties of the sisal fibers can be induced by means of different modification methods. When the treated fibers were incorporated into an epoxy matrix, mechanical characterization of the laminates revealed the importance of two types of interface: one between fiber bundles and the matrix and the other between the ultimate cells. In general, fiber treatments can significantly improve adhesion at the former interface and also lead to ingress of the matrix resin into the fibers, obstructing pull-out of the cells. As a result, the dependence of laminate mechanical properties on treatment methods becomes complicated. On the basis of a detailed analysis, the relationship between optimized fiber treatment and performance improvement of sisal composites was proposed.