Multifunctionality of Additively Manufactured Kelvin Foam for Electromagnetic Wave Absorption and Load Bearing

Rationally engineered porous structures enable lightweight broadband electromagnetic (EM) wave absorbers for countering radar signals or mitigating EM interference between multiple components. However, the scalability of such structures has been hindered by their limited mechanical properties resulting from low density. Herein, an additively manufactured Kelvin foam-based EM wave absorber (KF-EMA) is reported that exhibits multifunctionality, namely EM wave absorption and light-weighted load-bearing structures with constant relative stiffness made possible using bending-dominated lattice structures. Based on tuning design parameters, such as the backbone structures and constituent materials, the proposed KF-EMA features a multilayered 3D-printed design with geometrically optimized KF structures made of carbon black-based backbone composites. The developed KF-EMA demonstrated an absorbance greater than 90% at frequencies ranging from 5.8 to 18 GHz (average EM wave absorption rates of 95.89% and maximum of 99.1% at 15.8 GHz), while the low-density structures of the absorber (≈200 kg m^-3 ) still maintained a compression index between the stiffness and relative density (n = 2) under compression. The design strategy paves the way for using metamaterials as mechanically reinforced EM wave absorbers that enable multifunctionality by optimizing unit-cell parameters through a single and low-density structure.