Effect of surface treatments on interfacial properties of flax fiber-reinforced composites

Flax fiber has become increasingly attractive as reinforcement in polymer matrix composites. Due to its lighter weight, flax fiber-reinforced composites can perform similar to glass fiber-reinforced composites on a specific property comparison. In order to maximize the mechanical performance of the flax-reinforced composites, different fiber surface treatments have been investigated by many studies. In this study, four different chemical modifications were selected to compare difference on the mechanical performance between flax/vinyl ester composites and E-glass/vinyl ester composites. Different unidirectional flax fiber/vinyl ester and E-glass/vinyl ester composites were produced via a modified vacuum-assisted resin transfer molding process. Higher specific properties of chemically treated flax fiber-reinforced composites over those of E-glass composites were obtained. Acrylic acid treatment increased both the interfacial shear strength and the interlaminar shear strength about 30% compared with untreated flax composites. It confirms that the specific mechanical properties of flax composites with a suitable surface modification were comparable with E-glass composites. In addition, a suitable composite processing procedure to manufacture the flax/vinyl ester composites was designed and fiber bundle pullout test for flax fiber composites were developed.