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Engineering Science in
Additive Manufacturing AM-CFRP structures for EMWA properties

A striking feature of these additive manufacturing- functional elements (e.g., frequency selective surfaces or
produced metastructures is their ability to incorporate resistive patterns) within multimaterial structures could
functional gradients and multiresonant behaviors, as seen enable novel absorption mechanisms. As multimaterial
in gradient metastructures and helical patterns. Such 3D printing technologies continue to mature, they will
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designs allow spatially varying mechanical properties, enable the creation of next-generation “smart” absorbers
enabling targeted energy dissipation across different with adaptive performance, opening new possibilities for
frequency ranges or load conditions. For example, the applications in reconfigurable stealth systems, tunable
modular metastructure and crisscross design highlight EMI shielding, and intelligent anechoic coatings. The
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the potential for scalable, reconfigurable systems that combination of computational design tools, advanced
can be adapted for specific industrial requirements. The material systems, and high-resolution multi-material
pyramidal array sandwich structure (PASS) integrates printing capabilities represents a powerful approach to
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lightweight, high-stiffness cores with energy-absorbing overcoming traditional limitations in microwave absorber
skins, a critical advancement for applications demanding design.
strength and weight efficiency. Figure 6 illustrates the results on electromagnetic
Recent advances in multimaterial additive microwave performance and electric and magnetic field
manufacturing have opened new possibilities for distributions of additively manufactured microwave
precisely controlling the electromagnetic wave absorption absorbers. Recent advancements in additive manufacturing
characteristics of 3D-printed structures. By strategically have enabled the development of highly specialized
combining materials with different dielectric and microwave absorbers with tailored electromagnetic
magnetic properties within a single structure, researchers properties. These metastructures, including the bamboo-
can create spatially graded impedance profiles that inspired design, multiresonant configurations, and gradient
significantly enhance broadband absorption performance. architectures, leverage geometric complexity to achieve
Several promising techniques have emerged, including: superior absorption performance across specific frequency
(i) Alternating deposition of conductive (carbon-filled) ranges. For instance, the bamboo-inspired metastructure
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and insulating polymer layers to create impedance- mimics natural fibrous systems to optimize impedance
matching transitions and multiple internal reflection matching, whereas the multiresonant design incorporates
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interfaces; (ii) localized incorporation of magnetic multiple resonant frequencies to broaden the absorption
nanoparticles (e.g., ferrites) in specific regions to introduce bandwidth. The gradient metastructure further refines
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magnetic loss mechanisms; and (iii) functionally graded this approach by spatially varying its properties to create
material distributions that provide smooth transitions a smooth transition in impedance, minimizing reflections
in complex permittivity. These approaches leverage the and enhancing energy dissipation. These innovations
unique capabilities of multimaterial extrusion systems or highlight how bio-inspired and computationally optimized
polyjet printing technologies that can precisely deposit designs can push the boundaries of microwave absorption,
different materials at voxel-level resolution. Experimental offering solutions for applications ranging from stealth
studies have demonstrated that such multimaterial designs technology to EMI shielding in sensitive electronic devices.
can achieve reflection losses exceeding −40 dB while It has been shown that the field distribution analyses reveal
maintaining structural integrity, representing a significant the structural features that control energy dissipation.
improvement over single-material absorbers. Cellular structures promote multiple scattering, gradient
The field of multimaterial printed absorbers designs enable progressive wave decay, and resonant
presents several promising research directions that elements create localized field enhancement. The most
remain underexplored. A key opportunity lies in effective absorbers (Figure 6C, 6D and 6G) balance these
developing dynamic absorption systems where the mechanisms, achieving both broadband performance
material composition or microstructure can be actively (>80% bandwidth coverage) and deep absorption
reconfigured in response to external stimuli (e.g., (>20 dB), with the gradient and honeycomb designs being
temperature, electric field, or mechanical stress). Another particularly noteworthy for maintaining performance.
frontier involves combining conductive polymers with These results collectively demonstrate that the additive
ceramic or elastomeric materials to create absorbers manufacturing process enables precise control over
with tunable properties under operational conditions. electromagnetic field manipulation through hierarchical
ML-assisted design could play a crucial role in optimizing and multimaterial architectures.
these complex multimaterial architectures by predicting The electric-loss honeycomb metastructure (ELHM)
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the optimal spatial distribution of materials for target and the double high-impedance surface-loaded honeycomb
frequency bands. In addition, the integration of embedded (DHHC) structure demonstrate the effectiveness of
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Volume 1 Issue 2 (2025) 11 doi: 10.36922/ESAM025160008