Modal analysis of honeycomb panels and the influence of boundary conditions on the calculation

Purpose: In this work we investigate the elastic properties of sandwich beams manufactured by using the LF Technology. Design/methodology/approach: The investigation of the behaviour of rectangular shaped sandwich specimens is focused on the modal analysis and the experimental determination of the samples damping properties. Panels are made by unique technique of dry lamination patented by Czech company 5M s.r.o. The Hexagonal cell honeycomb core is made of aluminium as well as the facesheets. The influence of the main directions of anisotropy and the different panel’s thicknesses on the natural frequencies are investigated. Findings: The results of experiments are compared with the theoretical calculations and finite element method(FEM)simulation results. Theories used for the calculations are the First-order shear deformation theory (FSDT) and the Reddy’s third-order shear deformation theory (TSDT). FEM model had mapped mesh with 20-nodes brick elements. Research limitations/implications: The results obtained from FEA were closest to the experimentally measured data, but still with a deviation. The main reason of different results are geometrical irregularities. While FEM model was too much idealistic, the specimens prepared for measurement were not precisely planar. The specimens with small thickness were more twisted and therefore we got bigger error in the measured data and consequently the bigger deviation in results. In the future, we would like to do further measurements to transfer the real specimen geometry with all irregularities to a FEM model and to do new computations. Originality/value: Originality of this work is modal analysis of honeycomb panels and the influence of boundary conditions on the calculation.