Polycarbonate Composites Reinforced with Spartium junceum L. Fibers: A Promising Material for the Automotive Industry

The growing demand for sustainable materials has intensified research into natural fiber-reinforced polymer composites as alternatives to conventional fossil-based plastics. In this study, polycarbonate (PC) composites reinforced with Spartium junceum L. (SJL) fibers were developed and systematically characterized to evaluate their potential for automotive applications. Composites containing 5-20 wt % of randomly oriented short SJL fibers were prepared and analyzed in terms of thermal, mechanical, and morphological properties. Dynamic mechanical analysis revealed increased stiffness with rising fiber content, accompanied by a slight reduction in glass transition temperature. Tensile testing showed significant improvements in strength and Young's modulus, with optimal performance observed at 10-15 wt % fiber loading, attributed to improved fiber dispersion and interfacial adhesion. At higher fiber content (20 wt %), mechanical performance declined due to fiber agglomeration and reduced stress transfer efficiency. Thermal analysis indicated good compatibility between SJL fibers and the PC matrix, although a gradual decrease in thermal stability was observed with increasing fiber content. Scanning electron microscopy confirmed generally adequate fiber-matrix interaction, particularly at intermediate fiber loadings. Swelling tests demonstrated minimal water uptake, indicating preserved hydrophobicity of the composites. Overall, the results highlight the potential of SJL fibers as an effective, sustainable reinforcement for polycarbonate composites, offering improved mechanical performance while contributing to environmentally friendly material solutions for the automotive industry.