Genetic-algorithm-optimized honeycomb-reinforced metamaterial aerogel for broadband microwave absorption

Aerogel absorbers are attractive for lightweight electromagnetic wave attenuation, but their structural brittleness and limited geometric stability remain major constraints for engineering use. Simultaneously improving mechanical robustness and broadband absorption remains challenging. Here, we present a metamaterial aerogel composite that integrates mechanical reinforcement with broadband electromagnetic wave absorption. A parametric unit-cell model, governed by four coupled geometric variables, was constructed to span a continuous family of shapes from uniform slab through frustum to pyramid. A genetic algorithm searched this multi-dimensional design space to maximize effective absorption bandwidth (EAB) over 2–18 GHz under a 10 mm thickness constraint, converging on an optimized frustum configuration. The optimized geometry was fabricated as a polyimide/multi-walled carbon nanotube metamaterial aerogel (PCMA) and further integrated with aramid honeycomb to form the corresponding polyimide/multi-wall carbon nanotube (PI/CNT) metamaterial aerogel composite (PCMAC) by in-situ infiltration, freeze-drying, and thermal imidization. Mechanical tests further show that PCMAC-9.6 reaches compressive and nominal flexural strengths of 4.3 MPa and 0.80 MPa, respectively, exceeding both the empty honeycomb and the pure PCMA control. Compared with pure PCMA, PCMAC-9.6 exhibits an approximately 70–80% higher compressive strength and more than fourfold higher nominal flexural strength. These results demonstrate a practical route to multifunctional composites that combine broadband absorption with load-bearing capability for aerospace applications.