Structural modeling of sandwich panels with additively manufactured strut-based lattice cores

Abstract

Sandwich panels are lightweight structures used in the aerospace and the automobile industry. Global competition in these industries and the pressure to reduce material consumption and costs require new lightweight concepts and technologies to apply in sandwich panels. One of these new technologies is additive manufacturing (AM). The freedom of design provided by AM means that new structures such as strut-based lattices can be used as cores for sandwiches. These filigree structures cannot be fabricated using conventional manufacturing processes. Furthermore, fewer manufacturing steps are required through the use of additive manufacturing. Since all parts of the sandwich are manufactured in one step, the bonding process can be eliminated. However, the behavior of strut-based lattices as cores in sandwich panels is still unknown. Therefore, a new computational model is needed to predict all occurring stresses and displacements in sandwich panels to avoid failure of the sandwich structure. In the framework of linear elasticity, an analytical model for the calculation of stresses and displacements in cores of sandwich panels is developed in this study. By de-homogenization of the continuum core, the stress in lattice struts can be determined. In contrast to the most common laminate theories, the presented model enables the calculation of both transverse shear and normal stresses in the sandwich core since the transverse normal stress is of high importance for the design of the core when the sandwich is subjected to concentrated transverse forces. The obtained results can be used to optimize the design of lattice cores in sandwich panels employing additive manufacturing.