Thermal-based efficient modeling for mechanical properties of thermoplastic polymers in material extrusion

Abstract

The process-induced void defects play an important role in the mechanical properties of thermoplastic polymers fabricated by material extrusion (ME). Thus, it is meaningful to accurately and efficiently determine the impact of void defects on the ultimate mechanical properties of ME-printed parts. However, the straightforward relation between process parameters, void density, and mechanical properties remains unclear. In this paper, semi-analytical modeling is presented to efficiently predict the effective properties of ME-printed thermoplastic polymers. The void density related to process variables in the ME process is numerically determined based on a thermal sintering model. Subsequently, the effective properties of as-printed thermoplastic polymers are analytically predicted using the unit-cell-based homogenization method. The predicted results by the proposed semi-analytical model are validated by the comparison with experiments and finite element analysis. Furthermore, the effect of primary printing parameters on the degree of fusion, void density, and effective properties is examined. The results show that the elevated extrusion and substrate temperatures, as well as the decreased printing speed, layer height, and nozzle radius, contribute to the higher degree of fusion, leading to lower void density and superior elastic properties. In addition, moderate feeding speed and environmental temperature can enhance the elastic properties of ME-printed thermoplastic parts. These results offer useful guidelines for the design and manufacturing of thermoplastic parts with high performance.