LCR Meter Research Articles

Patterns of stability in complex contagions

Contagions refer to the spread or transmission of diseases, behaviors, beliefs, or emotions. While some contagions easily propagate throughout entire populations, others seem to be more constrained and propagate only within specific parts of the population. This arises not just because of different transmission rates but because of qualitative differences in the mechanisms with which contagions propagate throughout a network. Diseases typically propagate through single connections, while behaviors and beliefs often necessitate multiple connections for further propagation, termed complex contagions. In this paper, we propose a graph reduction method to reduce a network to include only connections immediately relevant to the propagation of a complex contagion. Through repeated application, we obtain structures that remain stable under the reduction, allowing us to define and measure for any given network, (i) strongly contagious components, (ii) weakly contagious components, and (iii) bridge components. Information about the size and location of these components can be used as a meaningful basis to assess and prevent the potential spread of harmful contagions as well as incentivize the spread of beneficial contagions.

Nanocomposite marvels: Miniaturized high bandwidth microstrip patch antenna for X-band applications

Zinc aluminate (ZnAl2O4) is widely recognized as a ceramic in high demand across various microwave applications. Furthermore, blending dielectric materials with ZnAl2O4 has demonstrated improvements in its dielectric properties, offering promising potential for advancing microstrip patch antenna technology. This paper presents the fabrication and characterization of a sol-gel composite nanoparticle consisting of titanium dioxide (TiO2) and zinc aluminate (ZnAl2O4) for use in a microstrip patch antenna designed for X-band applications. The composite nanoparticle, with a molecular composition of xTiO2(1-x)ZnAl2O4 where x = 8 %, was investigated using X-ray diffraction (XRD), revealing dominant peaks corresponding to ZnAl2O4 and TiO2 with a calculated crystallite size of 16.9 nm. Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS) were employed to assess functional groups, morphology, and elemental composition of the nanoparticles. The dielectric properties of the nanoparticles, characterized by a dielectric permittivity of 20.2 and a dielectric loss of 0.19, were measured using an LCR meter. These nanoparticles were utilized to fabricate a prototype patch antenna, exhibiting promising performance in both simulated and measured results. The fabricated patch antenna operated at 8.51/8.49 GHz with a return loss (RL) of − 25.94/−19.97 dB, featuring an enhanced bandwidth of 2.62/2.87 GHz and a voltage standing wave ratio (VSWR) below 2. Additionally, the antenna demonstrated a gain of 2.14, directivity of 3.58, and radiation efficiency of 59.7 %, making it suitable for X-band applications.

System reliability analysis of Cable-stayed bridge using pair Copula and ICLHS with unequal weights under seismic loading

Considering the correlation between different components, quantifying the failure probability of a high-level hyper-static structure under non-stationary seismic loading is of great significance in guiding earthquake-resistant design and fortification of bridges. In this study, a high-pier and large-span railway cable-stayed bridge in the mountainous region were employed to evaluate the seismic performance. First, the basic theoretical methods of the non-stationary random seismic motion simulation, equivalent extreme value theory based on extreme value distribution (EVD), improved Latin hypercube sampling (ICLHS) with unequal weighted fractional moment estimation and Pair Copula technique are presented. Second, the finite element analysis model of the cable-stayed bridge was established based on the OpenSees platform, the seismic response samples of the bridge were calculated under three levels of seismic ground motion to determine the first passage failure probability of the main components of the bridge under the design failure modes. Finally, the Pair Copula function was introduced to estimate the seismic system reliability of the cable-stayed bridge. The optimal Copula type that can describe the correlation between the bridge components was selected through goodness-of-fit tests such as AIC, BIC, and the minimum distance method. The failure probability of the entire system was obtained by calculating the selected Copula function type under seismic loading.

Fatigue life prediction method for reinforced concrete deck slabs subjected to repeated moving wheel loads and failing in shear

AbstractAs bridge deck slabs experience the direct impact of repeated concentrated wheel loads, they are more susceptible to fatigue‐related damage than other bridge components. In this context, a fatigue life prediction method for reinforced concrete (RC) bridge decks has been developed based on failure mechanisms of RC slabs tested under moving wheel loads. Initially, the formulas encompassed shear strength and S–N equations, accommodating variations in environmental and support conditions, are proposed to facilitate the fatigue life prediction of slabs exposed to constant moving wheel load. Subsequently, a model for shear strength degradation formulated using experimental findings on beam‐like elements is utilized in predicting the fatigue life of slabs subjected to stepwise moving wheel loads. The validity of the proposed method was established by comparing its results with previous experimental data. Notably, compared with the existing prediction equation, the proposed method exhibited more accurate fatigue life prediction results.

LOW FREQUENCY DIELECTRIC PROPERTIES OF AGRICULTURE SOIL CONTAMINATED BY POTASH CHEMICAL FERTILIZERS

Present paper investigates the impact of potash (KCl) contamination on the low-frequency (100 Hz - 1 MHz) dielectric properties of agricultural soil from the western Dhule district, India. Soil samples were spiked with varied KCl concentrations (0, 5, 10, and 20 mg) and analyzed using an LCR meter to measure dielectric constant, impedance, dielectric loss, and admittance. Results demonstrate a proportional increase in dielectric constant with increasing KCl concentration, indicating enhanced polarization within the soil matrix. Conversely, impedance and admittance displayed opposite trends, with impedance decreasing and admittance increasing as KCl concentration rose. Dielectric loss also exhibited a positive correlation with KCl content. This comprehensive investigation sheds light on the dynamic interplay between soil composition and dielectric properties under varying potash concentrations, contributing valuable insights to agricultural and environmental sciences.

Assessment of reliable wave climate at jetty on open coasts: role of 2D spatio-temporal spectrum

ABSTRACT The development of coastal roads and bridges is important to overcome traffic congestion in densely populated coastal cities like Mumbai. In the present study, the importance of assessment of wave conditions required for the extension of jetties to facilitate the transportation of bridge components to build the sea link bridge during non-monsoon season is envisaged so that zero downtime for operability at jetties is ascertained. Coupled hydrodynamic spectral wave model (Telemac-2D and TOMAWAC) used to hindcast waves reveals that the application of spatio-temporal varying 2D directional spectrum (from ERA-5) over the offshore boundary as a forcing function helps in propagation of realistic wave climate of Mahim Bay, Mumbai. Coupling of the TOMAWAC-ARTEMIS model is essential to obtain reliable wave conditions near the jetties (nearshore) for predominant directions. The study reveals that under existing conditions, downtime at proposed jetties will be for 30 days wherein Hs ≥ 0.3 m. As such to achieve zero downtime, the existing bund on the seaward side of jetties was extended optimally (70 m) so that smooth operability for the entire non-monsoon is achieved. Thus, application of spatio-temporal varying 2D spectrum in optimising the length of the guide bund has been found promising for speedy transportation of proposed bridge components. The study also reveals that there is an insignificant climatological impact on wave conditions.

Enabling efficient regional seismic fragility assessment of multi‐component bridge portfolios through Gaussian process regression and active learning

AbstractRegional seismic fragility assessment of bridge portfolios must address the embedded uncertainties and variations stemming from both the earthquake hazard and bridge attributes (e.g., geometry, material, design detail). To achieve bridge‐specific fragility assessment, multivariate probabilistic seismic demand models (PSDM) have recently been developed that use both the ground motion intensity measure and bridge parameters as inputs. However, explicitly utilizing bridge parameters as inputs requires numerous nonlinear response history analyses (NRHAs). In this situation, the associated computational cost increases exponentially for high‐fidelity bridge models with complex component connectivity and sophisticated material constitutive laws. Moreover, it remains unclear how many analyses are sufficient for the response data and the resulting demand model to cover the entire solution space without overfitting. To deal with these issues, this study integrates Gaussian process regression (GPR) and active learning (AL) into a multistep workflow to achieve efficient regional seismic fragility assessment of bridge portfolios. The GPR relaxes the probability distribution assumptions made in typical cloud analysis‐based PSDMs to enable heteroskedastic nonparametric seismic demand modeling. The AL leverages the varying standard deviation to select the least but most representative bridge‐model‐ground‐motion sample pairs to conduct NRHA with much‐improved efficiency. Both independent and correlated multi‐output GPRs are proposed to deal with bridge portfolios with seismic demand correlations among multiple components (column, bearing, shear key, abutment, unseating, and joint seal). Considering a single benchmark highway bridge class in California as the case study, the AL‐GPR framework and the associated component‐level fragility results are investigated in terms of their efficiency, accuracy, and robustness. The fragility results show that 70 AL‐selected samples would enable the GPR to derive bridge‐specific fragility models comparable to the ones using the multiple stripes analysis approach with 1950 ground motions considered for each individual bridge. The AL‐GPR model also successfully captures the physics of how bridge span length, deck area, column slenderness, and steel reinforcement ratio would change the damage state exceedance probabilities of different bridge components. The efficiency of AL stems from the fact that, with the multi‐output independent GPR, a stable and reliable fragility model can be achieved using 50 AL‐selected samples compared to at least 270 randomly chosen samples. The proposed methodology advances the state of the art in enabling more efficient and reliable regional seismic fragility assessment of multi‐component bridge portfolios.

Assessment of maximum and minimum hanger forces in a triple-cable suspension bridge under live load: Analytical algorithm with manta ray foraging optimization

Triple-cable suspension bridges (TCSBs) are widely used in sea-crossing, island-linking projects with extra-long spans and ultra-wide decks. Their safe operation requires sufficient resistance of all bridge components (towers, cables, girders, and hangers) to static/dead and cyclic/live loads. Therefore, reliable assessment of maximum and minimum axial forces acting on each hanger is topical. This study proposes an analytical algorithm for assessing the internal forces and deformations of a TCSB. Specific steps and formulae for solving the coefficients are described by taking the estimation of girder response under random eccentric line loading as an example. Parameters of the suspension bridge under dead load are treated as known quantities. Actual engineering scenarios, including girder displacements along the bridge, are analyzed and discussed in detail. Basic unknown quantities are determined via governing equations under conditions of elevation differences’ closure and conservation of main cables’ unstressed lengths, yielding direct solutions for deformations of the main cables, girder, towers, and hangers. The proposed analytical model’s feasibility is verified via the finite element method. Optimal solutions to the above equations are derived by the manta ray foraging optimization (MRFO) algorithm to find the most unfavorable load distributions for all vehicle lanes of the bridge and the maximum and minimum axial forces of random hangers. Finally, the proposed method is successfully applied to a TCSB with a 1600 m main span under two operating conditions. The most unfavorable load distributions and the maximum and minimum axial forces of hangers at the mid-span and at the quarter-span point are estimated. The calculation results are compared against those obtained by the influence surface method, showing their good correlation and superiority of the proposed method in computation workload.

Bond-slip behavior of steel reinforcing bars in ultra-high performance concrete for field-cast connection of precast bridge decks

In Accelerated Bridge Construction (ABC), Ultra-High Performance Concrete (UHPC) is often used for connecting precast concrete bridge components, including deck portions of the Deck Bulb-T girders. An alternative low-cost non-proprietary UHPC has been proposed for use in place of the proprietary UHPC for connecting the precast components. The pullout behavior of steel reinforcing bars in closure pour with typical range for embedment lengths is studied for both proprietary and non-proprietary UHPC materials.

Innovative sensor design for reliable detection of formaldehyde adulteration in milk

This research presents a straightforward and cost-effective sensor design for the detection of harmful chemical adulterants in raw milk, with a focus on formaldehyde, a common preservative. The proposed sensor design involves a minimal sample volume of 4 ml and utilizes a low-cost assembly with two nickel electrodes within a plastic cuvette. Electrochemical Impedance Spectroscopy (EIS) was conducted with an LCR meter to record three key electrical parameters: impedance (Z), phase angle (θ), and parallel plate capacitance (Cp). Testing was conducted in a controlled laboratory environment at temperatures between 25 to 27 °C for both unadulterated and adulterated milk samples. The results reveal that Z is the most sensitive parameter, capable of detecting formaldehyde adulteration as low as 0.5%. Conversely, θ and Cp effectively detected adulteration levels exceeding 3%. A noteworthy finding is a consistent and proportional increase in Z ranging from 2.2% to 26.4% as the formaldehyde concentration increases from 0.5% to 10% across a wide frequency range from 10 kHz to 200 kHz. This method offers a dependable and efficient approach to quality control, ensuring the safety and integrity of milk products.

Indirect frequency estimation by time-shifted accelerations subtraction: Generalization of the methodology and numerical application on a Warren truss bridge

In the context of Structural Health Monitoring (SHM) of transportation infrastructures, bridge eigen frequencies are commonly adopted as diagnostic indices. Under this regard, as a cost-effective identification methodology, indirect SHM, which consists in the use of sensors installed on running vehicles, is attracting attention. In particular, methods relying on the use of two or more on-board sensors may suppress the influence of track irregularity, which is a remarkable drawback for indirect SHM, and improve the identification accuracy. However, the combination characteristics of the two on-board sensors is still an open issue to be addressed. Also, in many studies, test bridges consist of simple girders, and there are few verifications on complex structures, such as truss bridges. The first contribution of this study is the analytical and generalized expression of the operational range defining the use of time-shifted signals subtraction operation for indirect frequency estimation. After the outcomes provided by this formulation were confirmed by the results obtained from a 2D explanatory example, the proposed procedure was further validated through three-dimensional train-track-bridge dynamic simulations. For this purpose, 3D FE model of a real existing Warren truss bridge, dynamically validated through experimental tests, and a 3D multi-body rail vehicle were adopted. From an engineering standpoint, a relevant result of this study found is that the coexistence of proper sensors onboard positioning and sufficient target bridge component excitation revealed to be crucial for the success of an indirect frequency identification procedure which is based on time-shifted accelerations subtraction.

Preparation and study of the effect of pH value on structural, morphological, electrical and magnetic properties of CoFe2O4 nanoparticles prepared by sol-gel precipitation method

The present study reports the synthesis of cobalt ferrite nanoparticles (CoFe2O4 NPs) using the sol-gel precipitation process via mixing a stoichiometric ratio of cobalt chloride (1 M) and ferric chloride (2 M). The molar of ferric to cobalt was mentioned (2:1) and then 2 M of sodium hydroxide was added. The structural and morphological features of the material were assessed using X-ray diffraction (XRD), Scanning electron microscopy (SEM), and atomic force microscopy (AFM). The electrical properties were analyzed using an LCR meter, while the magnetic properties were measured using a vibrating sample magnetometer (VSM). Fourier-transform infrared spectroscopy (FTIR) investigated the material's molecular vibrations. The X-ray diffraction (XRD) analysis revealed that all the samples exhibited a cubic spinal structure, and no additional peak was detected. Interestingly, the average size of the crystallites (D) decreased from 17.74 nm to 16.58 nm as the pH level increased from 7 to 13. This finding provides important insights into the behaviour of the tested samples under different pH conditions. The formation of the ferrite spine was confirmed by FTIR spectroscopy, with the primary detected bands (408.92–470.65 cm−1) attributed to the octahedral complexes and (516.94–588.31 cm−1) assigned to the tetrahedral ones. The dielectric and imaginary part of the dielectric constant decreased with increasing pH values excluding samples prepared at pH = 11. All samples with different pH values exhibit resonance peaks at frequencies up to (1 KHz). The magnetic measurements carried out by the VSM instrument, the result show that the saturation magnetization increases with increasing pH and the higher saturation magnetization is 68 emu. g1.

An Estimation Method of High-Order LC Circuits in Power Electronic Converters

This paper proposes a parameter estimation method for high-order LC circuits conducted during the power-OFF of power electronic converters. It is based on a battery-powered compact signal injection unit and a circuit modeling method to estimate the LC circuit parameters. The proposed method aims for LC component condition monitoring in applications with routine-based maintenance or frequent ON/OFF operation (e.g., wind power, photovoltaic, traction systems). Compared to LCR meters and impedance analyzers, the proposed method has a significantly lower implementation cost and does not require disassembly of components. Moreover, it is a converter-level method in which the signal injection unit only needs to connect the converter inputs or outputs. Compared to power-ON LC parameter estimation methods, the proposed one is non-invasive without adding any hardware or software algorithm that may introduce new risks to converter operation. This method can handle the converters with high-order LC structures (e.g., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{nd}$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4^{th}$</tex-math></inline-formula> -order) in converter power-OFF state, which has not been achieved by existing power-OFF solutions. Therefore, the proposed method is promising for the specific applications of interest mentioned above. The parameter estimation algorithm and signal injection unit design are presented. The experimental results indicate that the estimation errors of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{nd}$</tex-math></inline-formula> -order equivalent circuit, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3^{rd}$</tex-math></inline-formula> -order equivalent circuit, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4^{th}$</tex-math></inline-formula> -order equivalent circuit are lower than 1.6%, 2.5%, and 3%, respectively. The estimated LC parameters can be further used as inputs for operation optimization or condition monitoring of the converters.

Effect of Addition of Seaweed (Sargassum sp) Charcoal with Pure Graphite on the Electrical Properties of Graphene Oxide Synthesized by the Modified Hummer’s Method

Graphite is the primary raw material used to create graphene oxide. However, other biomass sources can also be used to create or combine the carbon source. Seaweed (Sargassum sp.), which has a decent carbon content, was used in this study as the biomass used as a carbon source for mixing. The objective of this research is to ensure how adding seaweed charcoal will affect the electrical characteristics of graphene oxide. The modified Hummer process was used to create the materials. There are four different compositions available: pure graphite (100%), 70:30 (graphite and seaweed), 60:40 (graphite and seaweed), and 50:50 (graphite and seaweed). The product of graphene oxide variations made from other compositions will be compared to those of 100% graphite composition. The result demonstrated that the addition of seaweed charcoal to the graphene oxide synthesis was successful. It can be seen from some of the characteristics of graphene oxide at an angle of 2Ɵ by XRD testing. In the FTIR test, it was discovered that the graphene oxide sample contained C-O, C=O, C=C, and O-H functional groups, and in the SEM test, peeling was discovered on the sample surface as a result of the oxidation process. The addition of seaweed charcoal with pure graphite synthesized by the modified Hummers method affects the electrical properties of the resulting graphene oxide. The material's conductivity value and the area capacitance value of the graphene oxide material both drop in the LCR Meter characterization instrument.

Studies on silver-doped magnesium ferrite utilizing the sol–gel process in terms of structure, magnetism, electricity, and electrochemistry

Silver added magnesium ferrite (Mg1-xAgxFe2O4) nanofine grains were prepared by the sol–gel technique from magnesium, silver, and ferrous precursor materials, maintaining the pH value that was subsequently investigated for sensing applications. X-ray diffraction (XRD) analysis of the ferrite samples showed (Mg1-xAgxFe2O4) cubic spinel structure, larger crystallite size, and other characteristics. Using Fourier transform infrared spectroscopy, the active and functional groups with potential stretching analysis were extracted (FTIR). Using an energy dispersive X-ray (EDAX) spectrum and a scanning electron microscope (SEM), the surface characteristics, features, and the samples purity were examined. The magnetic behavior was examined using the vibrating sample magnetometer (VSM) in relation to pertinent parameters like saturation magnetization (Ms), coercivity (Hc), and retentivity (Mr). It was found that the greater Ms in 1.0 is ferromagnetic. The LCR meter was used to estimate the dielectric constants (ε'&ε''), loss (tanδ) with AC conductivity (σAC), and cyclic-voltammetry was used to assess the electrochemical behavior of the samples. A study is conducted on potential polarizations at both ranges of frequencies. The acquired facts are thoroughly analyzed and comprehended.

Random bridge generator as a platform for developing computer vision-based structural inspection algorithms

Recent advances in computer vision algorithms have transformed the bridge visual inspection process. Those algorithms typically require large amounts of annotated data, which is lacking for generic bridge inspection scenarios. To address this challenge efficiently, this research designs, develops, and demonstrates a platform that can provide synthetic datasets and testing environments, termed Random Bridge Generator (RBG). The RBG produces photo-realistic 3D synthetic environments of six types of bridges randomly, automatically, and procedurally. Following relevant standards and design practice, the RBG creates random cross-sectional shapes, converts those shapes into bridge components, and assembles the components into bridges. The effectiveness of the RBG is demonstrated by producing a dataset (RBG Dataset) containing 10,753 images with pixel-wise annotations, rendered in 250 different synthetic environments. Significant diversity of the photo-realistic bridge inspection environments has been achieved, while all structural components strictly conform to the definitions derived from structural engineering documents. The use of the RBG dataset has been demonstrated by training a deep semantic segmentation algorithm with 101 convolutional layers, showing successful segmentation results for both major and minor structural components. The developed RBG is expected to enhance the level of automation in bridge visual inspection process. The Python code for RBG is made public at: https://github.com/chenghaojia2323/Random-Bridge-Generator.git.

PWHT influence on welding residual stress in 45 mm bridge steel butt-welded joint

To investigate the spatial distribution of welding residual stress (WRS) and effect of post welding heat treatment (PWHT) on WRS relaxation in the welded components of steel bridges, a 45 mm-thick Q345qD butt-welded specimen was manufactured. Experimental measurement and numerical simulation methods were employed to examine specimen surface and internal WRSs. The simulated results exhibited good agreement with the measured ones, confirming the rationality of the numerical simulation process. Subsequently, through the PWHT simulation in ABAQUS, the evolution of WRS during PWHT was comprehensively analyzed and the effect of PWHT parameters on the stress relaxation was studied. The measured and simulated results show that the longitudinal welding residual stresses (LWRSs) are tensile in the weld region and compressive away from the weld. High-value stresses are mainly concentrated on specimen surfaces and the mid-thickness. Transverse welding residual stresses (TWRSs) present multi-layered distribution, alternating between tension and compression within the weld region. WRS reduction mainly occurs during the heating stage of PWHT, with slight decrease during the holding stage and an increase during the cooling stage. Optimizing PWHT parameters, including temperature, and holding time, heating/cooling rates, proved effective in achieving substantial WRS relaxation.

Efficient in-site laser scanning scheme with adaptive angular resolution for long-span bridge geometry measurement

For geometrical measurements on long-span bridges, Terrestrial Laser Scanning (TLS) using conventional scanning approach yields the model with over-dense points in close regions and point redundancy in background. This not only hampers the efficiency of on-site scanning but also complicates data post-processing. This study introduces an optimised scanning scheme incorporating automatic identification of bridge key components and fine scan planning with adaptable angular resolutions. A novel method for TLS pose calibration, leveraging geometric feature partitioning and image template matching is proposed, which aids in projecting bridge component labels from the design model to the scan model in the TLS’s view. Considering the substantial disparities in scanning distances across different regions, a multi-segment scan planning is proposed through the clustering of spherical angles and desired angular resolutions. The effectiveness of the proposed method is demonstrated through a field test on a long-span bridge under construction, specifically for deck height measurements.

Structure of the γ-tubulin ring complex-capped microtubule.

Microtubules are composed of α-tubulin and β-tubulin dimers positioned head-to-tail to form protofilaments that associate laterally in varying numbers. It is not known how cellular microtubules assemble with the canonical 13-protofilament architecture, resulting in micrometer-scale α/β-tubulin tracks for intracellular transport that align with, rather than spiral along, the long axis of the filament. We report that the human ~2.3 MDa γ-tubulin ring complex (γ-TuRC), an essential regulator of microtubule formation that contains 14 γ-tubulins, selectively nucleates 13-protofilament microtubules. Cryogenic electron microscopy reconstructions of γ-TuRC-capped microtubule minus ends reveal the extensive intra-domain and inter-domain motions of γ-TuRC subunits that accommodate luminal bridge components and establish lateral and longitudinal interactions between γ-tubulins and α-tubulins. Our structures suggest that γ-TuRC, an inefficient nucleation template owing to its splayed conformation, can transform into a compacted cap at the microtubule minus end and set the lattice architecture of cellular microtubules.

First study of quantitative relationship between electric polarization and electromagnetic interference (EMI) shielding effectiveness of CFRP

This study investigates the electric polarization, including direct current (DC) and alternating current (AC), and electromagnetic interference (EMI) shielding capabilities within the microwave range (2.5–3.9 GHz) of cross-ply continuous carbon fiber-reinforced polymer (CFRP) composites, constructed by stacking prepreg composites. The DC conductivity of CFRP was evaluated using a multimeter, while the AC relative permittivity was measured with electronic test equipment (LCR meter). To describe the relationship between shielding effectiveness and polarization behavior, the EMI shielding of CFRP was assessed using the waveguide method, presenting a quantitative description of this relationship for the first time. Results indicate a decrease in DC conductivity with increasing specimen thickness due to increasing defects. Conversely, AC permittivity increases with specimen thickness, attributed to a rise in charged carriers and associated carrier-atom interactions. Skin depth δ, at a given thickness, follows a trend of initial decrease and subsequent increase with rising frequency; at a given frequency, it increases with decreasing specimen thickness. The interaction between CFRP and radiation is primarily reflective, with the reflection coefficient being much higher than the absorption coefficient across the frequency range, escalating with specimen thickness. Shielding effectiveness (SET) and absorption loss (SEA) display an initial increase followed by a decrease with rising frequency, whereas reflection loss (SER) sees a slight increase. For the smallest thickness, SEA per unit thickness exceeds 3120 dB/m and 7960 dB/m using specimen and carbon thickness, respectively. The absorption loss predominantly arises from the interaction of the electric field with electric dipoles formed by carrier-atom interaction at defects.