The aim of the present paper is to study the vibration behavior of a sandwich structure with honeycomb core experimentally and numerically with different design parameters. The natural frequency and damping ratio were obtained. Core height, cell angle and face thickness were considered as design parameters. Finite element models for the honeycomb sandwich were developed and analyzed via ANSYS finite element analysis (FEA) software. Response Surface Method (RSM) is used to establish numerical methodology to simulate the effect of the design parameters on natural frequency and damping ration. The employment of (RSM) provides a study of the effect of design parameters on natural frequency and damping ratio, numerical modeling of them in term of design parameters and specifying optimization condition. The experimental tests were conducted on sandwich specimens for the validity goal of the previous models created via the finite element analysis. The obtained results show that the natural frequency is directly proportional to the core height and face thickness, while it is inversely proportional to cell angle, Vice versa for damping ratio. Moreover, the optimum value of natural frequency (209.031 Hz) as minimum and damping ratio (0.0320) as maximum were found at 4.8855 mm of core height, 26.770 cell angle and 0.0614 mm face thickness.

Sandwich structures have been widely used as lightweight composite parts in the aerospace and shipbuilding engineering for their high capacity of stiffness, strength and energy absorption. There are three different criteria in bending crashworthiness for sandwich structure, namely peak bending load, maximum deflection and energy absorption. In this paper, the crashworthiness criteria of sandwich structure were evaluated theoretically and numerically based on failure mode maps. A failure mode map for the loading under three-point bending was constructed, depicting the reliance of the failure mode and the load upon the ratio of the skin thickness to the span length and the relative density of honeycomb. The finite element models for the sandwich panel with a honeycomb core were developed and analyzed via Ansys soft-ware package. The obtained result elucidated a good agreement between these models and the theoretical solution, where the error ratio was not exceeded 5%.To explore the effect of honeycomb parameters on the crashworthiness criteria of sandwich structure, several parameters have been selected, including the core height, the size of cell and the thickness of cell wall. In order to obtain the optimum solution of crashworthiness, Design of Experiment (DOE) software with the technique of Response Surface Methodology (RSM) was used. Results showed that the optimum value of peak bending load (25310 N) as maximum, deflection as minimum (0.8976 mm) and energy absorption as maximum (9.9949 J) were found at 29.2424 mm core height, 5 mm cell size and 1 mm cell wall thickness. Finally, the present study provides a new basis for more studies upon the optimization of the crashworthiness of sandwich structures.