A powder-scale multiphysics framework for powder bed fusion of fiber-reinforced polymer composites

Additive manufacturing of fiber-reinforced polymer composites has garnered great interest due to its potential in fabricating functional products with lightweight characteristics and unique material properties. However, the major concern in polymer composites remains the presence of pore defects, as a thorough understanding of pore formation is insufficient. In this study, a powder-scale multiphysics framework has been developed to simulate the printing process of fiber-reinforced polymer composites in powder bed fusion additive manufacturing. This numerical framework involves various multiphysics phenomena such as particle flow dynamics of fiber-reinforced polymer composite powder, infrared laser–particle interaction, heat transfer, and multiphase fluid flow dynamics. The melt depths of one-layer glass fiber–reinforced polyamide 12 composite parts fabricated by selective laser sintering are measured to validate modelling predictions. The numerical framework is employed to conduct an in-depth investigation of pore formation mechanisms within printed composites. Our simulation results suggest that an increasing fiber weight fraction would lead to a lower densification rate, larger porosity, and lower pore sphericity in the composites. A powder-scale multiphysics framework has been developed to simulate the printing process of fiber/polymer composites in powder bed fusion, encompassing powder recoating, melting, and coalescence. The simulation serves to understand pore formation mechanisms in printed composites and unravel that gas entrapment–induced pores exhibit nearly spherical shapes in polymer-rich regions and irregular shapes in fiber-rich regions. [Display omitted]