Key Takeaways & Executive Findings
- •• • The biomimetic concave basalt fiber-reinforced composite (BC-BFRC) achieves an effective absorption bandwidth (EAB) of 14.7 GHz (3.3–18 GHz) at reflection loss < −10 dB, a 26.7% improvement over planar BFRC, covering 91.9% of the S–Ku band, enabling multi-band radar stealth. • • The composite maintains stable broadband absorption (reflection loss < −8 dB) across incidence angles from 0° to 45° in the 4–18 GHz range, ensuring performance under oblique radar illumination. • • The flexural strength reaches 239.2 MPa, attributed to basalt fiber reinforcement, addressing the mechanical fragility and coating detachment issues of conventional MAMs. • • The broadband absorption mechanism is attributed to impedance gradient between layers and energy capture by the biomimetic concave structure, providing a design blueprint for structure-function integrated MAMs.
Abstract
The radar stealth performance of weaponry is crucial to their battlefield survivability, jointly determined by the effective absorption bandwidth (EAB) and mechanical properties of microwave-absorbing materials (MAMs). However, conventional MAMs often suffer from narrow EAB and absorption coatings prone to detachment. Herein, inspired by the wing scales of butterfly, we develop a biomimetic concave basalt fiber-reinforced composite (BC-BFRC) that delivers both broadband absorption and superior mechanical performance. Remarkably, the BC-BFRC achieves an EAB (reflection loss < −10 dB) of 14.7 GHz (3.3–18 GHz), which is 26.7% higher than the conventional planar structure (planar BFRC) and covers 91.9% of the S–Ku band. It maintains stable broadband absorption across incidence angles of 0°–45° (reflection loss < −8 dB at 4–18 GHz) and is insensitive to the incident direction. In fact, the broadband absorption originates primarily from impedance gradient between the layers and energy capture induced by the biomimetic concave at bottom. Critically, the composite exhibits a flexural strength of 239.2 MPa, enabled by basalt fiber reinforcement. This work provides a novel biomimetic strategy and feasible pathway for realizing structure-function integration of MAMs, enabling advanced radar stealth and electromagnetic shielding applications.
1. Introduction
Conventional microwave-absorbing materials (MAMs) rely on dispersing absorbent fillers within a matrix, yielding coatings that exhibit high absorption only at narrow resonant frequencies. This limitation, coupled with poor environmental adaptability and susceptibility to delamination, restricts their effectiveness against modern multi-band radar threats. Enhancing absorption by modifying intrinsic material properties alone has reached a plateau, necessitating structural innovations that simultaneously address mechanical integrity and absorption bandwidth.
Structural MAMs, which integrate load-bearing fibers and tailored geometries, offer a promising route to overcome these bottlenecks. By introducing fibers such as basalt, mechanical strength is improved, while specific structural designs optimize impedance matching and promote multiple scattering and polarization losses. This study draws inspiration from butterfly wing scales, which employ periodic microstructures to manipulate electromagnetic waves, to fabricate a biomimetic concave basalt fiber-reinforced composite. The concave architecture, combined with a gradient impedance design, achieves ultra-broadband absorption and high flexural strength, providing a feasible pathway for advanced radar stealth applications.
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Shuibin Chen, Qigang Han (2026). Biomimetic concave basalt fiber-reinforced composite integrating ultra-broadband absorption and excellent mechanical properties inspired by wing scales of butterfly. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3737-9
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Frequently Asked Questions
What is the specific improvement in effective absorption bandwidth (EAB) of the biomimetic concave structure compared to a planar counterpart, and how does this translate to operational frequency coverage?
The biomimetic concave basalt fiber-reinforced composite (BC-BFRC) achieves an EAB of 14.7 GHz (3.3–18 GHz) at reflection loss < −10 dB, which is 26.7% higher than the planar BFRC. This covers 91.9% of the S–Ku band, enabling operation against multiple radar frequency bands.
How does the composite maintain absorption performance under oblique incidence, and what is the angular tolerance?
The BC-BFRC maintains stable broadband absorption with reflection loss < −8 dB across incidence angles from 0° to 45° in the 4–18 GHz range, demonstrating insensitivity to incident direction, which is critical for real-world radar scenarios.
What is the flexural strength of the composite, and how does basalt fiber reinforcement contribute to mechanical robustness?
The composite exhibits a flexural strength of 239.2 MPa, enabled by basalt fiber reinforcement. This addresses the mechanical fragility and coating detachment issues common in conventional MAMs, ensuring durability in harsh battlefield environments.
What are the primary mechanisms responsible for the ultra-broadband absorption observed in this biomimetic structure?
The broadband absorption originates primarily from an impedance gradient between layers and energy capture induced by the biomimetic concave structure at the bottom. These mechanisms enhance impedance matching and promote multiple scattering and polarization relaxation losses.
How does this biomimetic design compare to existing structural MAMs in terms of scalability and practical implementation?
The use of basalt fibers, which are cost-effective and commercially available, combined with a relatively simple concave architecture, suggests potential for scalable fabrication. The demonstrated dual functionality of load-bearing and stealth positions this composite as a practical candidate for integration into weaponry and electromagnetic shielding applications.
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