Simulation-supported optimization of interlayer diffusion and crystallization in nanosilica-reinforced polylactic acid (PLA) manufactured by material extrusion

Material extrusion (MEX) additive manufacturing has emerged as a promising approach for fabricating customized polymer components. However, optimizing interlayer bonding and crystallization remains a significant challenge, particularly for polylactic acid (PLA), due to competing effects of thermal history, crystallization kinetics, and limited interlayer diffusion. In this study, a simulation-supported interlayer diffusion model is proposed to elucidate the effects of processing parameters and material modifications on the interfacial diffusion and mechanical performance of PLA and nanosilica-reinforced PLA (PLA-S) nanocomposites. A time-dependent thermal field was established through finite element simulation, capturing the dynamic temperature evolution of printed layers. Based on this, a temperature-dependent diffusion-based theoretical framework was developed to quantify interlayer diffusion and its relation to crystallization behavior. The results revealed that although nanosilica accelerates crystallization, it simultaneously reduces interfacial diffusion during printing, the improved intrinsic stiffness of the nanocomposite compensates for the reduced diffusion, resulting in enhanced mechanical performance under optimized conditions. This work establishes a quantitative framework linking thermal simulation, crystallization kinetics, and mechanical evaluation, offering a strategy for optimizing processing-structure-property relationships in polymer-based additive manufacturing. • Nanosilica accelerates PLA crystallization but hinders interfacial diffusion. • Optimal strength is achieved when diffusion surpasses the critical threshold. • The results offer a general framework for process–structure-property optimization.