Thermal–mechanical reliability and crystallinity evolution in annealed jute/PLA FDM bio-composites
摘要
Understanding the relationship between thermal behavior, crystallinity, and mechanical reliability is critical for optimizing bio-based composites. This study presents a novel integration of annealing-induced crystallinity evolution with probabilistic fatigue reliability modeling for jute fiber-reinforced polylactic acid (PLA) composites fabricated using fused deposition modeling (FDM). The composites, containing 10, 20, and 30% fiber volume, were thermally annealed between 80 and 120 °C for durations of 30–90 min to enhance molecular ordering and interfacial stability. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed a notable increase in crystallinity, from 14 to 32%, and an improved thermal stability with decomposition onset shifting from 350 °C to 370 °C after annealing. The optimized condition of 20% fiber content annealed at 100 °C for 60 min exhibited the best balance between crystallinity and mechanical durability. Under cyclic loading, this composite achieved a 42% increase in median fatigue life and maintained more than 85% stiffness retention beyond 105 cycles. Monte Carlo simulations and Bayesian calibration identified fiber fraction as the dominant uncertainty driver with a sensitivity index of 0.89, while the reliability index β increased from 1.9 to 3.1. These findings establish a direct link between thermal transitions, crystallinity evolution, and fatigue reliability. The proposed framework offers a thermally guided and reliability-based design strategy for developing high-performance, sustainable FDM bio-composites for load-bearing and structural applications.