Bio-inspired microwave maze composite via additive manufacturing for robust and oblique-incidence broadband microwave absorption

Abstract To meet the growing demand for structurally integrated microwave absorbers that combine robust load-bearing capacity with broadband and oblique-incidence absorption, this work designs and fabricates a bio-inspired composite featuring a hierarchical porous architecture. Drawing inspiration from the fiber-reinforced, periodically arrayed microstructure of the weevil beetle shell, the triply periodic minimal surface (TPMS)-based topological structures are additively manufactured using short-cut carbon fiber-reinforced polyamide (SCF/PA). Among the TPMS architectures evaluated, the primitive shell-type structure was selected for its optimal balance of broadband absorption and mechanical robustness, achieving a reflection loss (RL) of − 59.65 dB at 13.23 GHz and an effective absorption bandwidth (EAB, RL ≤ − 10 dB) of 30.04 GHz at a thickness of 24.7 mm, in addition to a flexural strength of 13.81 ± 1.20 MPa. A sandwich composite was then fabricated by laminating glass fiber and carbon fiber fabrics onto the TPMS core. This composite exhibits a flexural strength of 34.16 ± 0.64 MPa with a density of 0.36 g/cm 3 , while maintaining an EAB of 30.92 GHz and an RL of − 36.61 dB at 12.78 GHz (25.72 mm). Under oblique incidence, it retains 75.6% of its normal-incidence bandwidth (23.38 GHz) for transverse electric (TE) polarization and 121.8% (37.67 GHz) for transverse magnetic (TM) polarization at an incident angle of 65°. This superior performance comes from the synergy of several factors: electric loss from the SCF reinforcement, the microwave maze effect (multiple reflections and extended propagation paths occur within the TPMS porous network), and optimized impedance matching enabled by the fabric layers. Overall, this bio-inspired, multi-scale design strategy offers a promising route toward integrating broadband, oblique-incidence microwave absorption with enhanced structural functionality in complex service environments.