Thermo-mechanical modeling of lattice-core sandwich panels in powder bed fusion

Abstract

Residual stresses play detrimental roles in the mechanical performance of lattice-core sandwich panels (LCSPs) via powder bed fusion (PBF), owing to the laser-induced high-temperature gradients. Thus, it is essential to understand the thermo-mechanical behavior of LCSPs during PBF. However, the relation between process settings and the mechanical response of as-printed LCSPs has not been systematically investigated. In this study, an integrated thermo-mechanical modeling is developed to effectively capture the strut stress and deformation of PBF-built LCSPs. The key advance is that the effective thermo-mechanical field within printed LCSPs is first determined based on the homogenization-based differential quadrature method, where the structure-dependent thermophysical and mechanical properties of lattice cores are considered. The effective displacement is used to directly calculate strut stresses through a de-homogenization process. The accuracy of the predicted results is verified by the comparison with the literature. Furthermore, the effect of process parameters, geometrical dimensions, and strut structures on the thermo-mechanical behavior of pyramidal and vertically reinforced pyramid LCSPs is demonstrated. The results show that the strut stress and vertical warpage increase with the higher energy density, length-to-thickness ratio, and vertical strut addition, while decreasing as the inclined angle and environmental temperature enlarge. These findings can offer a guideline for the high-quality printing of LCSPs with desired mechanical performance and dimensional accuracy.