## 1 Introduction
[20; 21] used a theoretical model of impedance analysis with Monte-Carlo simulations to account for microstructure variability and predicted transverse conductivity to be approximately \(\sim\)8 S/m. Accounting for the variability in microstructure and quantum tunneling phenomena is crucial for the accurate prediction of transverse conductivity [23]. When estimating the EMI shielding effectiveness (SE) at high frequencies (>1 GHz), relying on DC conductivity leads to inaccuracies due to the significant rise of the skin effect in an AC field as a result of induced eddy currents [24]. This phenomenon limits the flow of current to the outer surface of the conductor rather than a uniform distribution across the cross-section. Hence, an accurate prediction of the EMI shielding effectiveness of composites across a broad frequency spectrum is achievable solely through AC conductivity, and very limited work is reported in this area. [PERSON] et al. [8] employed a micromechanics model to predict the electrical conductivity in CNT-doped epoxy composites, showing a direct correlation between transverse electrical conductivity and frequency. The lack of a comprehensive model for predicting AC conductivity necessitates the need for a more accurate modeling approach that accounts for both microstructure variability and frequency dependence. Various techniques have been investigated to enhance the EMI shielding performance of composite structures. Some researchers have used metallic layers or conductive coatings to enhance the reflective component of EMI shielding [24; 25; 26]. As observed in a previous study by the co-authors [24], the incorporation of copper mesh improves the reflection component of EMI shielding effectiveness. [PERSON] et al. [25] have characterized the EMI shielding effectiveness of glass fiber reinforced polymer composites coated with aluminum, aluminum bronze and zinc. Their investigations show an enhanced SE of up to 60 dB from the baseline value of 7 dB. The major drawback associated with including metallic layers is that the structural strength is compromised due to its poor bonding with the composite ply. The use of a modified epoxy with magnetic or conductive filler materials such as CNTs has been investigated [27; 28]. [PERSON] et al. [27] studied the EMI SE of nanocomposites by varying the weight fractions of different filler materials, including multi-walled carbon nanotubes (MWCNTs), Fe\({}_{3}\)O\({}_{4}\), and Fe within the epoxy resin. Their work reported an upward trend of shielding effectiveness with increasing frequency by using CNTs, while the Fe and Fe\({}_{3}\)O\({}_{4}\)-doped composites showed a less frequency dependence. [PERSON] et al. [29] explored strategies for assembling two-dimensional metal carbide sheets (MXenes) to improve electromagnetic interference (EMI) shielding. They found that rGO/CoNi nanosheets exhibited a high absorption shielding effectiveness, achieving a value of 54.1 dB. Although these methods can be beneficial in enhancing both the electrical and mechanical properties of composites, they do not harness the full potential of carbon nanotubes at the laminate level [10; 11; 12; 13; 14]. This paper presents a novel approach for modeling the AC conductivity of BP-reinforced CFRP laminates accounting for quantum tunneling and skin effects. The paper is structured into two main sections: the first section introduces an equivalent circuit method for characterizing the frequency-dependent electrical conductivity of carbon fiber lamina. The CFRP microstructure is transformed into an equivalent circuit, and the effective impedance is analyzed to estimate the longitudinal conductivity. The transverse conductivity is determined using Monte Carlo simulations informed by quantum tunneling principles. The second section focuses on coupling the estimated conductivity values with electromagnetic wave propagation simulations to investigate the EMI SE of hybrid BP/CFRP samples. Finally, the EMI SE results are compared with an alternative shielding technique using copper mesh layers.