Comprehensive analysis of thermal properties and stability in palm fiber-reinforced PLA composites with bran filler for sustainable lightweight materials

This study investigates the dynamic and thermal stability of palm fiber-reinforced polylactic acid (PLA) composites enhanced with bran filler to develop lightweight and sustainable materials. Composites were prepared with varying bran filler content (5–25 g), while keeping fiber content constant (250 g) and adjusting the PLA matrix accordingly. Mechanical, thermal, and microstructural properties were analyzed. Among the samples, the composite with 15 g bran filler (S3) exhibited the best overall performance. It demonstrated superior fatigue strength (25 MPa at 5000 cycles), enhanced fiber-matrix adhesion, and reduced porosity. Dynamic mechanical analysis confirmed S3’s highest storage modulus (2400 MPa at 110°C) and damping factor (tan δ = 0.340 at 130°C), indicating excellent viscoelastic properties. Thermal analysis showed improved heat resistance, with the highest heat deflection temperature (134°C) and lowest thermal conductivity (0.65 W/mK). Thermogravimetric analysis further validated its superior thermal stability, with an onset degradation temperature of 350°C and the highest residual char (18%) at 500°C. These results highlight that moderate bran filler reinforcement optimizes composite performance, while excessive filler can reduce effectiveness. This study presents a novel approach to enhancing PLA composites, making them optimistic for sustainable applications such as automotive components, structural biocomposites, and biodegradable packaging.