Effect of surface treatments on the mechanical properties of natural fiber textile composites made by VaRTM method

Abstract

In this study, we aimed to improve the strength of textile composites by applying surface treatments on natural fibers. Natural fibers used were flax and hemp, and the matrix was an epoxy acrylate resin. The flax fiber textile was treated with acetone, laundry detergent, and aqueous solution of sodium hydroxide, because water repellent substances were adhered to the fibers. Hemp fiber textile was chemically-treated with polysilazane, silane coupling agent, and coated by polyvinyl alcohol (PVA). These treatments were carried out to improve the adhesion by treating the fiber surface. Natural fiber textile composites were made by a vacuum assisted resin transfer molding (VaRTM) method. After molding, the effect of washing process and surface treatments was verified by tensile tests. The most effective washing process was alkali-treatment with an aqueous solution of sodium hydroxide. The alkali-treated flax fiber composite had its tensile strength improved by 19.7% compared to the untreated fiber composite. However, the tensile strength and Young’s modulus of surface treated hemp fiber composite were reduced. The effect of PVA coating was examined by using a micro-droplet method. The interfacial shear strength of PVA-coated hemp fiber was reduced compared to that of untreated hemp fiber. In addition, the interfacial shear strength was reduced with increasing PVA content.