Analysis and design of high frequency periodically layered isolators in compression

Detailed finite element modal analysis of layered isolators is conducted to gain an improved understanding of three-dimensional effects in compression. Layered isolators exhibit transmissibility "stop bands", or frequency ranges with very low transmissibility. Comparison between onedimensional theory based on Floquet analysis and the three-dimensional finite element analysis indicates that stop band frequencies predicted using one-dimensional results can be highly inaccurate. Errors for isolators studied in this investigation were between 17-70%. Experimentally transmissibility measurements are obtained for two different layered isolators. Both isolators exhibit pronounced attenuation within stop band frequencies. Good correlation between three-dimensional finite element analysis and experimental data is obtained. Contrary to earlier one-dimensional analyses, material damping can play a significant role in peak attenuation levels. An efficient onedimensional analysis of layered isolators is developed. This analysis incorporates table look-up frequency corrections to account for three-dimensional elastic effects. A design optimization methodology is then developed for layered isolators subject to quasi-static stiffness constraints. A simulated annealing algorithm is employed to determine optimal material properties and layer thicknesses.