Loss mechanisms in low-fiber H-shaped absorbers and multi-angle microwave absorption control via array density

To overcome the bottlenecks in achieving broadband absorption and thin-profile design for high-temperature absorber-load-bearing integrated fiber composites, this paper presents an in-depth study on H-shaped fiber array structures composed of carbon fibers and silicon carbide fibers. By integrating the minimal aperture method with equivalent medium theory, an accurate extraction model for the equivalent electromagnetic parameters of non-uniform structures was established, resolving the challenge of electromagnetic parameter inversion for traditional all-metal backplane structures. Using nonlinear fitting methods, the contributions of conduction loss and relaxation polarization loss to dielectric loss were quantitatively analyzed. Results indicate that in the X and Ku bands, relaxation polarization loss is dominant, accounting for 63.73% of the total loss. The carbon fiber skeleton primarily dissipates energy through eddy current effects and ohmic losses induced by high conductivity, while silicon carbide fibers contribute to relaxation polarization loss via interfacial dipole reorientation polarization. Furthermore, constructing a 2.5 mm uniform-thickness multilayer gradient stack structure effectively mitigates impedance mismatch and significantly broadens the absorption bandwidth. Notably, under 20° oblique incidence, absorption performance improved by 1.8 times, reaching −32.5 dB from −17.8 dB. The effective absorption bandwidth increased by 1.7 times, broadening from 4.66 to 7.83 GHz. With a fiber content of only 4.536%, this structure achieves high-efficiency broadband absorption within a 2.5 mm thickness.