A novel engineered sandwich composite with ceramic-coated graphite fibre-reinforced face sheets and an auxetic core for enhanced broadband electromagnetic absorption: design using multiscale computational analysis

A novel sandwich composite is designed for enhanced broadband absorption using a multiscale computational analysis. The sandwich panel is configured with BaTiO₃ coated graphite fibre reinforced polymer (C-GFRP) composite, while BaTiO₃ material is used as the auxetic core material. A computationally efficient in-house tool based on the variational asymptotic method is used to homogenise the electromagnetic properties and evaluate the reflection loss characteristics of the proposed sandwich structure using the scattering matrices. A detailed parametric study of 300 analyses is conducted to identify the optimal sandwich panel configurations for achieving broadband reflection loss under the normal incidence of transverse electric (TE) and transverse magnetic (TM) polarised waves. Two different configurations have been obtained, satisfying the requirements of broadband reflection loss in the X-band frequency range. Configuration (a) V_f = 15% without any ceramic coating, and configuration (b) V_f = 20% with a ceramic coating volume fraction (C_f) of 70%. Configuration (a) and (b) maintained the desired reflection loss of greater than −10 dB up to an incidence angle of 40° and 60°, respectively. With the demonstrated capability of covering the entire broadband frequency range, the proposed configurations can serve as baselines to explore novel ceramic-based engineered composite architectures for broadband absorption applications.