Correlative Investigation on Dielectric-Mechanical-Morphological Characteristic for Kenaf-Glass-Hybrid Fibres Reinforced Epoxy Composite

Abstract

In recent years, there are many applications where synthetic fibres and natural fibres are used as reinforcing materials in composites, such as the automotive and aerospace industries, the medical industry, and the construction industry. While these hybrid fibres effectively enhance mechanical and electrical properties, research into electrical characteristics remains inadequate and is an ongoing endeavor. In this work, synthetic woven glass fibres and natural woven kenaf fibres were used to fabricate composite materials by vacuum infusion technique. The dielectric properties of three different substrates, glass fibres, kenaf fibres and glass/kenaf fibres reinforced epoxy composites were investigated at 0° orientation. The ENA Network Analyzer was used to measure dielectric properties in a wide microwave frequency range. The substrates were single-joint overlapped with an adhesive and then mechanically tested. The shear strength of the joint as a function of strain, was tested using a Shimadzu universal testing machine. Visual inspections were performed to determine the failure modes of the composites. The dielectric constant and loss factor of the glass fibre composite were the highest, while the kenaf fibre composite had the lowest value. When a small amount of glass fibres is incorporated into kenaf fibres, which is called a hybrid composite, the polarization increases and the mechanical strength also increases compared to the kenaf fibre composite. Scanning electron microscopy (SEM) of the fractured tensile tests was performed to understand the nature of the interfaces between glass, kenaf and matrix. The kenaf/matrix interface was heterogeneous but exhibited voids, resulting in low dielectric properties and mechanical strength. By inserting a small amount of glass fibres, the hybrid with kenaf fibres improve the dielectric constant by 20.7% and the dielectric loss factor by 27% compared with the kenaf fibre composite. The results also show that the composites exhibit a correlation between the dielectric properties, tensile strength, and the morphological nature of the interfaces.