Additive Manufacturing of Multifunctional Meta-Sandwich Composites—Lightweight, Load-Bearing and Broadband Electromagnetic Wave-Absorbing Structures

The use of lossy material-based mechanical metamaterials, featuring engineered porous geometries like an octet-truss, has emerged as a promising multifunctional structure for broadband absorption. The porous nature of these metamaterials not only improves mechanical characteristics but also enables structural electromagnetic wave attenuation through impedance matching, internal scattering, and reflection. However, the exposed cellular lattice structure poses challenges for real-world applications. Packaging the cellular structure as a sandwich panel is a viable solution to mitigate this challenge, as the additional faceplates increase mechanical strength and stiffness while protecting the cellular structure from the external environment. Despite this, the fabrication and assembly of multifunctional meta-sandwich composites remain challenging using conventional manufacturing processes such as cutting, engraving, dipping, molding, and heat treatment. In this study, we utilize multi-material additive manufacturing to present a multifunctional meta-sandwich structure as a seamlessly integrated component comprising functional faceplates and dielectric lossy material-based octet-truss geometries. This multifunctional structure is lightweight, load-bearing, and a high-performance broadband EM wave absorber. The EM responses are explored within the 4–18 GHz range, with varying material combinations and multilayers of the upper-lower faceplates and the octet-truss core. Numerical analysis elucidates the absorbing mechanisms of the meta-sandwich structures. The fabricated composite, in a thin, single-layer structure comprising a transmitting upper faceplate, a dielectric lossy core, and a reflecting lower faceplate, achieves an average absorption rate of 95.0% and a broadband reflection loss (≤-10 dB) over the entire measured bandwidth (5.8 – 18 GHz). Furthermore, flexural testing confirms superior bending resistance compared to conventional honeycomb structures. The multi-material meta-sandwich design will inspire versatile multifunctionality enabled by rationally combining mechanical metamaterials and functional housing.