Nanocomposites and nanomaterials

Optimization of multilayered electromagnetic shields using mesh adaptive direct search
Vovchenko L.L., Lozitsky O.V., Matzui L.Yu., Zagorodnii V.V.
Department of Physics, Taras Shevchenko National University of Kyiv.
64/13, Volodymyrska Street, Kyiv-01601, Ukraine. 
E-mail: vovch@univ.kiev.ua

Multilayered composite structures have been proven to have superior shielding properties, compared to bulk composites if the layers’ thickness and effective permittivity are set in a way to utilize electromagnetic interference between the layers at frequency ranges, where a specific transmission or absorption spectrum is required. This spectrum is essentially an objective function used in many mathematical optimization algorithms. In this work a modified mesh adaptive direct search algorithm [1] has been used to design 3-layered composite structures to obtain the highest absorption and to achieve frequency filtering of the EMR. This method does not require differentiability of the objective function, and thus is better suited for multilayered composites, where the required shielding spectra may have multiple local minimums in parameter space.
   
Figure 1. Optimized spectra of reflection loss (a) and shielding effectiveness (b) of multilayered samples. 
A number of multilayered samples were optimized for achieving i) the lowest reflection loss in range 30-40 GHz (Fig. 1a) and ii) the filtering of microwave radiation (Fig. 1b). The results show the possibility of designing the composites with specific shielding spectra, however the inaccuracies in manufacture of the composite layers may lead to significant mismatch between measured and modeled spectra.
1.	Audet, C., & Dennis, J. E. Mesh Adaptive Direct Search Algorithms for Constrained Optimization // SIAM J Optim.-2006.-17, N 1.-P. 188–217.