Numerical Simulation of the Influence of Shell Powder Doping on the Selective Laser Sintering Process of Polylactic Acid‐Based Composites

Polylactic acid (PLA) exhibits favorable melt processability and biodegradability, serving as a dominant polymer feedstock for selective laser sintering (SLS). Nevertheless, neat PLA suffers from inferior thermal conductivity, poor melt rheological stability, and chaotic dissipation of sintering stress. The sintered specimens are prone to defects including warpage, pores, and weak interfacial bonding, which degrade the dimensional accuracy and mechanical service stability of SLS parts. As a calcium carbonate‐based inert inorganic filler, shell powder integrates outstanding thermal properties, high elastic modulus, low cost, and eco‐friendly degradability, making it suitable for polymer modification in sintering processes. However, the multi‐field coupling mechanism whereby shell powder mediates the microstructural evolution of PLA composites during SLS remains unclear. Based on three fundamental theories, namely non‐equilibrium thermodynamics, viscoelastic rheological kinetics, and elastic stress wave propagation, this study incorporates multi‐field distribution of temperature, flow velocity, and pressure as well as dynamic monitoring data at characteristic measuring points. Centered on heterogeneous interface effects, the regulation mechanism of shell powder fillers throughout the entire SLS forming procedure of PLA‐based composites is investigated from three microscale dimensions: heat transport, melt mass transfer, and stress dissipation. Classical theoretical models are adopted to characterize the evolutionary laws of heat conduction, rheology, and stress within composite systems. The intrinsic mechanism by which fillers mitigate sintering defects and reinforce interfacial bonding strength is elaborated, providing theoretical support and mechanistic references for modifying laser‐sintered polymers with eco‐friendly inorganic fillers.