Fabrication and structural optimization of integrated gradient honeycombs with the conductive/absorbing coatings for ultra-wideband microwave absorption

With the advancement of complex radar reconnaissance and stealth technologies, research on microwave-absorbing materials (MAM) in a broad frequency range is in great demand, especially for lightweight honeycomb structures designed for aerospace applications. The challenge lies in achieving a balance between small thickness and wideband absorption in high-performance aramid honeycombs. This study proposes a novel approach known as the integrated gradient honeycomb structure (IGHS). The IGHS is designed based on the theory of impedance matching through electromagnetic parameter simulations of the graphene conductive/carbon black absorbing coatings and further optimized by tailoring the factors such as the height of the conductive/absorbing coatings, the square resistance of the conductive coatings, and the thickness of the absorbing coatings, all while maintaining an overall height of 15 mm. The optimized integrated gradient honeycomb is fabricated by employing an experimental anisotropic impregnation technique, achieving a reflection loss below –10 dB across the whole frequency range of 2.2–18 GHz, consistent with the simulated results, with the compressive strength of the structure reaching 4.76 MPa, along with shear strengths of 1.25 MPa and 1.72 MPa in the W-direction and L-direction, respectively. In the present work, a cyclical system integrating simulation and experimentation has been established, reducing the trial-and-error costs for researchers and offering valuable insights for the design of a gradient honeycomb structure (GHS) for wide-frequency microwave absorption.