Evaluation of two finite element formulations for a rapid 3D stress analysis of sandwich structures

For efficiently simulating the impact behavior of sandwich structures made from composite face sheets and a lightweight core a rapid and accurate 3D stress analysis is essential. For that reason, a three-layered finite element formulation based on plane stress assumptions was recently developed by Kärger et al. [Kärger, WA, Rolfes R, Rohwer K. A three-layered sandwich element with improved transverse shear stiffness and stress based on FSDT. Comput Struct, submitted for publication]. It has turned out, however, that under concentrated out-of-plane loads this element formulation lacks appropriate accuracy of stress results. Therefore, an improved finite element formulation is developed, which accounts for the full 3D stress state. In a post-processing routine, the transverse stresses are improved by using the Extended 2D Method, which was developed by Rolfes and Rohwer [Rolfes R, Rohwer K. Improved transverse shear stresses in composite finite elements based on first order shear deformation theory. Int J Numer Meth Eng 1997;40:51–60] and extended to a three-layered sandwich structure by Kärger et al.