The Effect of Fiber Surface Treatment on the Performance of Hemp Fiber/Acrylic Composites for Automotive Structural Parts

The use of natural fibers for polymer composite materials has increased tremendously in the last few years. This type of reinforcements offers many advantages such as low density, low cost, high specific strength and low environmental impacts. The performance of the natural fiber composites are affected by the fiber loading, the individual mechanical properties of each component (fiber and matrix), and the fiber and matrix adhesion. Concerning the interfacial interaction, natural fibers present a major drawback because of poor compatibility of fibers with most hydrophobic thermoplastic and thermoset matrix. Hemp fiber/acrylic composites were manufactured with sheet molding technique recently. Although mechanical tests give promising results, they exhibit low tensile strength resulting from a poor fiber/matrix adhesion. The moisture resistance property of the sheet molded composites also needs further improvement. In the present work, we propose surface modification of the hemp fibers to improve the surface adhesion and moisture absorption properties of these structural composites. The influence of various chemical treatment such as alkali, silane, SMA Imide resin (copolymers of styrene and dimethylamionopropylamine (DMAPA) maleimide), and fungal treatment were investigated. All type of treatments improved substantially the hydrophobic behavior of the fibers. The SMA treated samples show maximum improvement in their tensile strength and modulus.