Mechanical performance of epoxy matrix composites reinforced by physically and chemically treated hemp fiber

Hemp fiber is one of the most common reinforcements for polymer matrix composites and it is widely used in various applications due to its environmentally friendliness, favorable physical and mechanical properties. In spite of the numerous merits of the hemp fiber reinforced polymer composites, improvement of poor interfacial properties between the hemp fiber and polymer matrix is limited. The main objective of this work is to investigate the effect of increased fiber surface area and alkaline surface treatment on the mechanical performance of hemp fiber reinforced epoxy composites. An elevated temperature aqueous debundling treatment was employed to generate a large number of individual fibers from fiber bundles and was associated with a threefold increase in specific fiber surface area. The fiber dimension and surface properties were investigated through optical microscopy, confocal microscopy, and scanning electron microscopy. The effects of different debundling treatment times and additional alkaline treatment on the mechanical properties were studied. It was found that composites reinforced by the debundled hemp fiber with further alkaline treatment exhibited the best tensile and flexural properties in comparison to other composites reinforced with debundled hemp fiber without further alkaline treatment or with untreated hemp fiber.Highlights Provided a new physical method for separating hemp fiber bundle into individual hemp fibers using boiling water and blending. Debundled fibers resulted in a 3.5 times increase in fiber surface area for better bonding with epoxy matrix. Debundling process combined with chemical (alkaline) treatment to further improve the compatibility between individual fiber and epoxy. The effects of the debundling only, alkaline treatment only, and combined debundling + alkaline treatment on composite properties were studied. The effect of fiber treatments on mechanical properties of hemp fiber epoxy composites. image