Modeling and Measuring the Shielding Effectiveness of Carbon Fiber Composites

Abstract

We provide a model able to predict the shielding effectiveness (SE) of carbon fiber composite (CFC) panels made of stacked layers of conducting fibers. This model permits us to obtain simple formulas in which the only parameters needed are the sheet square resistance and the effective panel thickness. These tools let us to predict a minimum SE, which always increases with the frequency and therefore constituting the worst case, from an electromagnetic shielding perspective. Consequently, the measurement of minimum SE requirements can be simply measured with a micro-ohmmeter using an specific experimental setup which is also described here. Additionally, this method allows to measure very high SE falling far beyond the dynamic range of the values measurable with the most commonly used standard, the ASTM D4935. After describing the modeling technique and the different test setups used, a cross-validation between theoretical and experimental results is made for four different samples of CFC; two designed to test the modeling assumptions and two which are representative of the ones nowadays used in a real aircraft.

Recent advances in electromagnetic interference shielding properties of carbon-fibre-reinforced polymer composites—a topical review

“…In contrast to metals, shielding theory for carbon-fibre-reinforced materials remains largely undeveloped and most of the interpretations are still made with reference to the White model, bringing a degree of uncertainty due to significant disparity in the assumptions. Most of the existing theoretical work attempting to describe the shielding abilities of carbon-fibre composites is restricted to the plane wave shielding of periodic structures composed of multiple unidirectional (UD) plies at varying orientations [113][114][115][116][117][118][119][120][121]. The filamentary and stock-piled geometry of such structures gives rise to complicated resonant phenomena emerging from continuous reflections at different fibre locations [113].…”

“…The filamentary and stock-piled geometry of such structures gives rise to complicated resonant phenomena emerging from continuous reflections at different fibre locations [113]. The problem is intrinsically multiscalar and not yet resolved, even with the help of advanced computational methods and simulations [116]. At high frequencies, where the wavelength is comparable to the fibre spacing, microstructure-wave interactions are of particular importance, as they give rise to intra-ply resonance phenomena in multi-layered composites [113].…”

“…In addition, if the fibres are closely packed, there exists a proximity effect between currents induced in the fibres, which dominates at high frequencies. These phenomena require detailed knowledge of the specific parameters of the microstructure, such as fibre diameter and are not represented by any existing analytical model [116]. These factors, combined with the small fibre dimensions, mean that any numerical analysis at the fibre scale is extremely computationally intensive.…”

Characterization of Joints between Carbon Fiber Composite Parts Using a Microstrip Transmission Line Method

“…Just as the studies on the electromagnetic characterization of materials [ 8 , 9 , 10 , 11 ] and, in particular, on the electrical conductivity of CFC composites [ 12 , 13 , 14 , 15 , 16 ] have been multiplied, knowledge on the electromagnetic performance of the union of parts made of CFC structures is not as far developed compared to parts made of metal [ 17 ]. The study of these joints is fundamental because electrical discontinuities or preferential paths can produce changes in the aircraft electromagnetic behavior.…”

Homogenization of woven composites for shielding applications: the case of oblique incidence

“…Techniques combining analytical, numerical and/or experimental work can also provide estimations of composites EM response. For instance, in [12] measured parameters are implemented into an analytical formula to calculate the transmission coefficient of stratified carbon fiber composites. Experimental investigations can also be conducted separately to obtain estimates of transmission coefficients.…”