An investigation into instantaneously tuning the EMI shielding characteristics of CNT-based nanocomposite biofoams in the X-band range by strain loading

The electromagnetic interference (EMI) shielding of CNT-based nanocomposite biofoams is capable of being tailored instantaneously by mechanical loading. In contrast to tuning the EMI shielding via nanofillers or by decoration process, the strain-activated EMI tailoring characteristics possess enormous potential that still await to be explored. To reveal this tailoring mechanism, a multi-scale electro-magneto-mechanically coupled homogenization model is developed to tailor the EMI characteristics of CNT-based nanocomposite biofoams in the X-band range (8.2-12.4 GHz). In this development, the elastic moduli, complex conductivity, and complex permeability are all selected as the homogenization variables. Four categories of interface effects are considered, including imperfect interface bonding, electron tunneling, Maxwell-Wagner-Sillars polarization, and electron hopping. The predicted EMI tailoring characteristics are validated by the experiment of CNT/wheat flour nanocomposite biofoam over a wide range of stain loading. The effective EMI shielding behavior decreases with the compressive loading, but it increases with the tensile loading. It is found that a CNT content higher than the percolation threshold is necessary to tailor the EMI shielding behavior of this nanocomposite foam via strain loading. This study can provide innovative insights to tune the EMI shielding characteristics of CNT-based nanocomposite biofoams in X-band instantaneously.