Free vibration behaviours of composite sandwich plates with reentrant honeycomb cores

The free vibration behaviours of carbon fiber composite sandwich plates with reentrant honeycomb cores were explored by experiment, theory and finite element method (FEM) in present study. The composite sandwich plates with reentrant honeycomb cores were designed and fabricated through hot-press and secondary forming technology. The modal characteristics of composite auxetic honeycomb sandwich plates were tested under simply supported boundary conditions. Furthermore, the influences of relative densities and dimensions on the natural frequencies of composite auxetic honeycomb sandwich plates were studied. The equivalent moduli of the unit cell of reentrant hexagonal core were deduced. The free vibration control equation was derived to gain the natural frequencies of the sandwich plates by Zig-Zag theory. The theoretical results of the natural frequencies were obtained and compared with the experimental results and finite element calculation results. The results showed that the theory and FEM could estimate the natural frequencies of this kind of sandwich plates accurately. The natural frequencies of the sandwich plates raised as the increasing of relative densities and influenced by dimensions of the core.