Page 10 - ESAM-1-2

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

Table 1. Summary of electromagnetic microwave absorption mechanism in additively manufactured carbon fiber‑reinforced
polymer structures
Mechanism Description Typical Main parameters Advantages Limitations Optimization
type frequency strategies
range (GHz)
Impedance Minimizes reflection by Broadband Relative permittivity, Maximizes Sensitive to Graded porosity or
matching aligning material’s wave (2 – 18 GHz) permeability, microwave entry into frequency and multilayer designs
impedance with free thickness the material thickness variations
space
Attenuation Measures the Varies Dielectric/magnetic Stronger attenuation Balance with Optimizes carbon
constant microwaves lose energy loss, conductivity means better impedance matching fiber alignment and
in the material absorption infill density
Reflection loss Quantifies the Tunable for Surface impedance, A direct indicator Requires precise Designs metamaterial
microwave energy specific bands thickness of absorption thickness control surfaces (honeycomb,
absorbed rather than performance pyramids)
reflected
Dielectric loss Energy absorption Effective Dielectric loss Naturally high in Can cause an Adds nano-fillers like
through charge at higher tangent, conductivity CFRPs due to carbon impedance mismatch graphene; control
polarization and frequencies fibers fiber orientation
conduction
Magnetic loss Energy dissipation Best at 1 – 10 Magnetic loss Enhances Requires magnetic Incorporates ferrite
through magnetic GHz tangent, resonance low-frequency additives particles
interactions effects absorption
Interference Cancels waves through Narrowband Layer thickness, Enables thin Narrow effective Alternating layers
loss strategic phase (tunable) reflection phases absorbers bandwidth with precise thickness
differences
Abbreviation: CFRP: Carbon fiber-reinforced polymer.

2.4. Dielectric loss relationship between ε′ and ε′′ to properly depict the
Electromagnetic waves interact with a dielectric medium polarization relaxation impact in the electromagnetic
to create carriers that can conduct electricity through wave attenuation process. According to the classical Debye
the material. Figure 2 shows internal dielectric current theory using Cole–Cole images, each semicircle represents
and loss in various scenarios. When applied, an electric one polarization relaxation phenomenon. Typically, the
field causes a conduction current, which causes electrical polarization relaxation process is more robust when the
energy to dissipate and dielectric losses. Displacement Cole–Cole semicircle is larger and the electromagnetic
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or capacitance current is the phrase used to describe wave is incident on the absorber surface. The dielectric
the current that does not release energy when charged loss tangent is given by the ratio of the imaginary part
geometrically. Polarization relaxation is associated with (ε ′′) to the real part (ε ′) of the complex permittivity, as
the conduction current produced in an alternating electric expressed in Equation III.
field by EMA materials with a particular conductivity. It ε ''
appears as a polarized effect inside the electric field and is tan δ = ' (III)
e
caused by the loss of polarization. Dielectric relaxation loss ε
(tgδrel) will occur if the polarization rate is slower than the
electric field fluctuation rate. The current is connected to 2.5. Magnetic loss
the free charge and results in losses as conductivity losses In addition to dielectric losses, which indicate a material’s
(tgδ ) are produced by the medium’s conductivity. ability to sustain a magnetic field within a medium, magnetic
c
The net efficiency parameter of the energy transfer loss is a crucial part of the electromagnetic loss process.
process is the dielectric loss tangent angle (tanδ ). The The primary cause of magnetic loss in the microwave range
e
greater tanδ indicates enhanced coupling between is believed to be eddy current loss, which happens when
e
electromagnetic waves and the material within the an external electric field transforms the work done on a
absorbing body, resulting in increased loss and improved magnetic material into heat energy during magnetization
absorption performance. The relaxation process with or demagnetization. Eddy current loss (Co), which is the
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dipole and interfacial polarization is examined in the energy dissipation brought on by induced currents in a

Volume 1 Issue 2 (2025) 4 doi: 10.36922/ESAM025160008