The effect of simultaneous fiber surface treatment and matrix modification on mechanical properties of unidirectional ultra-high molecular weight polyethylene fiber/epoxy/nanoclay nanocomposites

Abstract

Nonpolar structure of ultra-high molecular weight polyethylene fiber leads to a weak interfacial adhesion in ultra-high molecular weight polyethylene fiber reinforced epoxy composite. Herein, synchronized fiber and matrix modifications were utilized so as to improve the interfacial adhesion, resulting in promoting mechanical properties of these composites. For this purpose, the surface of ultra-high molecular weight polyethylene fiber was chemically treated with glycidyl methacrylate and the epoxy resin was modified through incorporation of different contents of nanoclay. The mechanical properties results showed that individual modification, either fiber or matrix, can just lead to improvements around 36.74% and 10.54% in tensile strength as well as 14.28% and 4.27% in tensile modulus, respectively. However, the ultimate outcome of the study revealed that much higher improvement can be achieved in synergistic attitude. The highest enhancement around 48.31% and 26.76% in tensile strength and modulus were seen for the sample containing glycidyl methacrylate-treated ultra-high molecular weight polyethylene fibers as reinforcement and nano epoxy modified with 1 wt.% of nanoclay. Such observation could be attributed to the mechanical interlocking and chemical reaction which were arising from incorporation of nanoclay in matrix and chemical treatment of fiber surface, correspondingly. In this regard, fiber roughness and chemical bonds formed between treated fiber and modified matrix play a key role in improving interfacial adhesion. Moreover, the fractured surface of such composites studied by scanning electron microscope confirmed the mechanical results and showed that much more matrix was adhered to the fiber surface after treatment, indicating cohesive failure.