Anisotropic Samples Research Articles

Mechanical Properties and Constitutive Model for Artificially Structured Soils under Undrained Conditions

Triaxial tests are performed for remolded, artificially isotropic, and anisotropic structured samples under undrained conditions at confining pressures of 25, 100, and 200 kPa. Based on these test results, a binary-medium constitutive model is formulated based on homogenization theory and a breakage mechanism to describe the behaviors of structured soils. In this model, the binary-medium material is idealized as a representative volume element (RVE) composed of bonded elements, whose mechanical behaviors are expressed by the linearly elastic model, and frictional elements, whose mechanical behaviors are described by the double-yield surfaces constitutive model. The parameters of the bonded and frictional elements are determined from the test results of structured and remolded samples, respectively. The expressions for the breakage ratio and local stress coefficient matrix are introduced, and their parameters are provided. The computed results are compared with the test results, demonstrating that the model can reflect the main deformation features of structured soil relatively well, including the influence of anisotropy, gradual damage to particle bonding, and pore development.

Moisture penetration and distribution characterization of hard coal: a µ-CT study

Moisture content of rock/coal can change its mechanical properties and absorption capacities, which can directly affect gas diffusivity, change the stress distribution and hence cause significant impacts on the overall gas or coal extraction process. Observation of the water penetration process and water distribution in the coal matrix will be beneficial for the understanding of the fluid-solid coupling mechanism in hydraulic fracturing, aquifer cracking and coal seam infusion. However, the observation of water penetration process and the determination of water distribution mode were hard to be non-destructively achieved as coal is a non-uniform, inhomogeneous and un-transparent material. µ-CT imaging, which is based on variation of X-ray attenuation related to the density and atomic composition of the scanned objects, enables a four-dimensional (spatial-temporal) visualise of the heterogeneous and anisotropic coal samples. The primary aim of this paper is extending the application of µ-CT imaging to explore the moisture penetration and distribution within coal samples during water infusion process, which has been reported by very little literature. The working principle and procedures of CT imaging was firstly introduced. Then, the determination equation of moisture distribution based on density profile was established. The CT determined moisture content has been compared with weighting method for verification. The paper has demonstrated that µ-CT can be used for non-destructively imaging the moisture distribution within coal samples.

Experimental study and mechanism analysis on the effect of pre-curing time on the microstructure and mechanical properties of magnetorheological elastomers under compression

The effects of the pre-curing time before exposing the carbonyl iron particles (CIPs) filled liquid polydimethylsiloxane (PDMS) mixture to a preparatory magnetic field on the magnetorheological (MR) effects of the magnetorheological elastomers (MREs) were experimentally and theoretically investigated. The anisotropic MRE samples with different pre-curing time were firstly fabricated and their compressive MR effects were tested. The results showed that the longer pre-curing time induces the shorter and more irregular particle chains formed in the MREs, and the sample pre-cured for 20 min showed the maximum MR effect. Then based on the rheological characterization, a rheological model was proposed to predict the rheological property evolution of CIPs/PDMS mixture with respect to the pre-curing time, and a modified three-dimensional (3D) particle dynamics (PD) model was developed to simulate the particle structure evolution in the MRE mixtures under a preparatory magnetic field. The simulation results showed that short chains were first formed owing to the magnetic attraction between the adjacent particles. Then these short chains approached each other to form long chains and even thick chain-like clusters. The later process can be restrained by increasing the pre-curing time, thus more short and incompact particle chains are formed in the MREs. Lastly, simplified microstructure models representing the wavy chains were used to explore the effect of particle arrangement on the MR effect of the MREs under compression. It is found that the wavy chains with incompactly packed particles are beneficial for improving the MR effect owing to the strong transverse magnetic attraction between the neighboring particles. This work demonstrates that PD simulation is an efficiency method to predict the particle arrangement evolution in the MRE mixture, and the possibility to tailoring the microstructures of the MREs by adjusting the viscosity of MRE mixtures to improve their MR effects, while keeping a high zero-field modulus simultaneously.

Influence of normal force on magnetic-field-induced shear modulus of isotropic and anisotropic magnetorheological elastomers having spherical and non-spherical shape iron particles

ABSTRACT Isotropic and anisotropic magnetorheological elastomers (MRE) were prepared using spherical carbonyl iron (CI) particles and electrolyte non-spherical iron (EI) particles having a 60% weight fraction in silicon rubber. The pre-structured MREs were prepared under a constant magnetic field of 0.3 Tesla. A parallel-plate MR rheometer with a magneto-rheological cell was used to conduct dynamic measurements under different normal forces. All the data were recorded under 1 Hz frequency and strain amplitude of 0.1% (in the linear viscoelastic region), and normal force was varied from 1N to 10 N. Results show that the magnetic-induced shear modulus increases in both MREs with normal force for isotropic as well as anisotropic samples. However, in CIP-based MRE, the MR effect increases with a pre-structured sample, whereas for EIP-based pre-structured MRE, the MR effect decreases compared to isotropic samples. Nevertheless, the relative MR (RMR) effect decreases with normal force in both cases. The rate of decrease is different in CIP- and EIP-based MREs. A possible mechanism for the same is discussed in the paper.

Effects of Polarizer-Analyzer Configurations for FTIR Spectroscopy: Implications for Multiple Polarization Algorithms.

Polarized Fourier transform infrared (p-FTIR) spectroscopy is a widely used technique for determining orientational information in thin organic materials. Conventionally, a single polarizer is placed in the path of the incident light (termed the polarizer). Occasionally, a second polarizer is also placed after the sample (referred to as the analyzer). However, this polarizer-analyzer configuration has the potential to induce polarization-dependent variances in the final spectra beyond those that are expected, i.e., the squared-cosine relationship of absorptance with respect to polarization angle is no longer accurate. These variances are due to changes in the polarization state of the transmitted light induced by the sample and have yet to be explored in the context of p-FTIR. Consequently, this study employs both theoretical and experimental approaches to identify the effects of including a second polarizer in p-FTIR analyses of anisotropic organic samples. For thin samples, the most significant spectral variance arising from only birefringence is observed on the shoulders of the dichroic peaks. By adopting a crossed polarizer configuration, it is shown that there is potential to identify anisotropy of samples that are generally considered too thick for p-FTIR analysis by exploiting this feature. Furthermore, the squared-cosine relationship of absorptance with respect to the polarization angle is also shown to be inapplicable when a second parallel-oriented polarizer is included. Accordingly, a function that accounts for the second polarizer is proposed for multiple polarization techniques.

Producing Conventional and Transient Amino(mercapto)methyl Radicals by Addition of Muonium to a Crystalline Thioformamide (Mes*NHCH=S).

Muonium (Mu=μ+e-) is composed of a muon of light isotope of proton (μ+) and electron (e-) and can be used as a light surrogate for a hydrogen atom. In this paper, we investigated addition of muonium to a newly synthesized Mes*-substituted thioformamide (Mes*NHCH=S, Mes*=2,4,6-tBu3C6H2). Transverse-field muon spin rotation (TF-μSR) of a solution sample of the thioformamide confirmed addition of muonium to the sulfur atom leading to the corresponding C-centered radical [Mes*NHC(H)⋅-SMu]. Density functional theory (DFT) calculations assigned a conventional amino(mercapto)methyl radical, in which both nitrogen and carbon were slightly pyramidalized, and the calculated muon hyperfine coupling constant (hfcc) including the muon isotope effect was compatible with the experimentally determined parameter. However, the muon level-crossing resonance (μLCR) spectrum of an anisotropic crystalline sample indicated two paramagnetic species, and the major product showed the considerably larger muon hfcc compared with the conventional structure of the amino(mercapto)methyl radical. The unusual transient muoniated thioformamide with the larger muon hfcc that showed rapid relaxation could be only explained by a transient structure including planarization of the nitrogen and carbon atoms in Mes*NHC(H)⋅-SMu.

X-ray Diffraction Line Profile Analysis of Natural Calcite Minerals found in Southern Philippines by Williamson-Hall Method

This study employs the Williamson–Hall (W–H) models to examine the microstrains and crystallite sizes of CaCO3 occurring as calcite in limestone samples found in General Santos City and Sarangani Province, Southern Philippines. Using both the Uniform Deformation Model (UDM) and Uniform Stress Deformation (USDM) models, computations for average sizes were established to be identical, implying minimal strain influence. The consistency of resulting measurements extends to the microstrain, revealing uniform results for all samples. Correlation between crystallite sizes and microstrains in the calcite crystals was observed, where high-purity calcites exhibited larger crystallite sizes and microstrains. The crystallite sizes decrease with microstrains for calcites with higher Mg concentration, a finding that can be attributed to lattice distortion and the formation of defects. The release of stress forms these defects, thereby resulting in a reduction of microstrains. Moreover, the distinctly variable responses to strain exhibited by the samples could be influenced by either their anisotropic properties or other additional components. The W–H models, used jointly with UDM and USDM consistently predicted crystallite sizes, and thus offer valuable insights into the uniform stress responses of calcites. These promising results notwithstanding, USDM is shown to be especially relevant for anisotropic samples owing to the display deviations of crystallite sizes, a key feature of anisotropic natural calcites. The microscopic analysis is expected to provide additional understanding regarding the state of the limestone samples.

Tensile Properties of Isotropic and Anisotropic Magnetorheological Elastomer With and Without Magnetic Field Application

In this study, two variations of magnetorheological elastomer (MRE) tensile specimens were fabricated, differing in their isotropic and anisotropic configurations. The isotropic MRE exhibited randomly dispersed carbonyl iron particle (CIP), whereas the anisotropic featured longitudinally aligned CIP particles along the gauge length of the tensile sample. The formation of the anisotropic MRE involved utilizing an electromagnetic curing chamber, which facilitated the alignment of CIP particles during the elastomer curing process. A mold was specifically designed to produce samples conforming to the dimensions outlined in ASTMD412-F. Subsequently, a Finite Element Method Magnetics (FEMM) analysis was conducted to examine the magnetic flux within the curing device for the anisotropic MRE. Uniaxial tensile tests were conducted on both MRE types, both in the absence and presence of a 30 mT magnetic field applied transversely to the direction of CIP alignment. Results indicated that without a magnetic field, the anisotropic sample exhibited a slightly higher tensile strength, lower elongation, and higher modulus at 100% strain. However, when a magnetic field was introduced, the isotropic sample demonstrated a more pronounced increase in tensile strength, showing an 18.4% improvement compared to the 5.6% increase observed in the anisotropic sample. Similar trends were observed in the reduction of elongation, with a 14% decrease for isotropic and a 7% decrease for anisotropic samples. Additionally, the data on modulus at a 100% strain revealed a 22.3% increase in stiffness for the isotropic sample, while the anisotropic sample showed a 10.6% increase.

Real-time and calibration-free generalized terahertz time-domain spectroscopic ellipsometry

Spectroscopic ellipsometry is a high-precision and powerful optical characterization technique, which can be categorized into two fundamental types of standard and generalized ellipsometry. The latter can obtain the complete Jones matrix to investigate various anisotropic samples. However, terahertz generalized ellipsometry has traditionally relied on frequency-domain instrumentation, which is limited in bandwidth, complicated in polarization manipulation, and slow in operation. In this study, we propose a highly accurate and efficient terahertz time-domain generalized ellipsometer based on a polarization beam coupler-splitter configuration. It measures four independent complex spectra in real-time without mechanical movement, providing ultrahigh data throughput. Each polarizer-antenna unit constructively superimposes their filtering effect, resulting in a 45–65 dB extinction ratio that approaches the system dynamic range. The superb illumination and detection linearity provides an outstanding polarization accuracy and eliminates the need for complicated calibration. Reflection characterization of the magneto-optical properties of an InAs wafer demonstrates the generalized ability to simultaneously obtain multiple dielectric functions. Transmission ellipsometric imaging of liquid crystals subjected to an inhomogeneous electric field further highlights the excellent efficiency. The proposed technique significantly expands the capabilities of terahertz spectroscopy, paving ways to anisotropic materials, in situ monitoring, and polarization-sensitive devices.

Characterization of effective elastic constants and anisotropy directions for Wire Arc Additive Manufactured steel samples using RUS

In recent years, Resonant Ultrasound Spectroscopy (RUS) has been extensively applied to objects produced by additive manufacturing to characterize elastic material properties, detect defects or geometrical deviations. In this talk, we analyze samples that were produced using the wire-arc additive manufacturing (WAAM) process using different grades of steel wires. Resonance spectra were obtained and allowed to classify samples as either elastically isotropic or anisotropic. Detailed investigation on anisotropic samples (produced with 316L wire) under an orthotropy hypothesis showed that the samples were markedly softer along the layer deposition direction. Subsequent investigation using EBSD confirmed the results obtained with RUS. They also allowed to quantitatively model the elastic constants using the Voigt-Reuss-Hill averaging theory, which were in good agreement with the ones obtained using the RUS inverse problem.

Study on anisotropy orientation due to well-ordered fibrous biological microstructures.

Most biological fibrous tissues have anisotropic optical characteristics, which originate from scattering by their fibrous microstructures and birefringence of biological macromolecules. The orientation-related anisotropic interpretation is of great value in biological tissue characterization and pathological diagnosis. We focus on intrinsic birefringence and form birefringence in biological tissue samples. By observing and comparing the forward Mueller matrix of typical samples, we can understand the interpretation ability of orientation-related polarization parameters and further distinguish the sources and trends of anisotropy in tissues. For glass fiber, silk fiber, skeletal muscle, and tendon, we construct a forward measuring device to obtain the Mueller matrix image and calculate the anisotropic parameters related to orientation. The statistical analysis method based on polar coordinates can effectively analyze the difference in anisotropic parameters. For those birefringent fibers, the statistical distribution of fast-axis values derived from Mueller matrix polar decomposition was found to exhibit bimodal characteristics, which is a key point in distinguishing the single-layer birefringent fiber sample from a layered, multioriented fibrous sample. The application conditions and interference factors of anisotropic orientation parameters are analyzed. Based on the parameters extracted from the orientation bimodal distribution, we can evaluate the relative change trend of intrinsic birefringence and form birefringence in anisotropic samples. The cross-vertical bimodal distribution of the fast axis of anisotropic fibers is beneficial to accurately analyze the anisotropic changes in biological tissues. The results imply the potential of anisotropic orientation analysis for applications in pathological diagnosis.

On the physical meaning of the geometric factor and the effective thickness in the Montgomery method

The Montgomery method is extensively employed to determine the electrical resistance tensor of anisotropic samples. This technique relies on two essential parameters describing an isotropic system: the geometric factor (H1) and the effective thickness (E). The numerical values of these parameters are intricately linked to the dimensions of an isotropic block equivalent to the studied anisotropic specimen. While these parameters hold importance, the physical interpretation of these terms still lacks clarity. In this study, we utilized the finite element method to simulate electrical transport experiments across samples of various shapes. Utilizing the Electric Currents physics interface in the COMSOL program, we were able to provide a comprehensive analysis of the physical meaning of these parameters to accurately determine the electrical properties of thin films and wafers. The presented findings related to the physical interpretation of H1 and E terms make substantial contributions to the field of electrical transport experimental techniques, which are fundamental to design advanced materials for technological applications and understand their physical properties.

Stretchable Magneto-Mechanical Configurations with High Magnetic Sensitivity Based on "Gel-Type" Soft Rubber for Intelligent Applications.

"Gel-type" soft and stretchable magneto-mechanical composites made of silicone rubber and iron particles are in focus because of their high magnetic sensitivity, and intelligence perspective. The "intelligence" mentioned here is related to the "smartness" of these magneto-rheological elastomers (MREs) to tune the "mechanical stiffness" and "output voltage" in energy-harvesting applications by switching magnetic fields. Hence, this work develops "gel-type" soft composites based on rubber reinforced with iron particles in a hybrid with piezoelectric fillers such as barium titanate. A further aspect of the work relies on studying the mechanical stability of intelligence and the stretchability of the composites. For example, the stretchability was 105% (control), and higher for 158% (60 per 100 parts of rubber (phr) of barium titanate, BaTiO3), 149% (60 phr of electrolyte iron particles, EIP), and 148% (60 phr of BaTiO3 + EIP hybrid). Then, the magneto-mechanical aspect will be investigated to explore the magnetic sensitivity of these "gel-type" soft composites with a change in mechanical stiffness under a magnetic field. For example, the anisotropic effect was 14.3% (60 phr of EIP), and 4.4% (60 phr of hybrid). Finally, energy harvesting was performed. For example, the isotropic samples exhibit ~20 mV (60 phr of BaTiO3), ~5.4 mV (60 phr of EIP), and ~3.7 mV (60 phr of hybrid). However, the anisotropic samples exhibit ~5.6 mV (60 phr of EIP), and ~8.8 mV (60 phr of hybrid). In the end, the composites prepared have three configurations, namely one with electro-mechanical aspects, another with magnetic sensitivity, and a third with both features. Overall, the experimental outcomes will make fabricated composites useful for different intelligent and stretchable applications.

Compression cycling and magnetic response of single crystalline Ni-Mn-Ga particles/polymer composite: In-situ and ex-situ study

Ni-Mn-Ga particles/polymer composites are new magnetostrain active materials suitable for actuation and sensing. In the present work, we prepared mechanically anisotropic samples of the “30 vol% single crystalline Ni-Mn-Ga particles/silicone” composite material and systematically studied their cyclic stress-strain (S-S) evolutions along and perpendicular to the particle chains, while monitoring changes of magnetization curves. Four different compression cycling routes with the strain amplitude of 30% were explored. Magnetic measurements were served as the probes to indirectly detect microstructure changes of composite samples, whereas X-ray micro-CT images, alongside dimensions control of samples, were used for direct microstructural observations. The influences of the compression cycling routes on the parameters of S-S behaviors, such as an output stress, effective stiffness, and stress hysteresis, were revealed. It was found that the composite material after achieving equilibrium showed a rather good compression cycling stability of the mechanical and magnetic properties. It was revealed that composites being strongly deformed either along easy-magnetization axis (along the particle chains) or along hard-magnetization axis (perpendicularly to the particle chains) exhibited a magnetically harder behavior along the particle chains and magnetically easier behavior in the orthogonal direction, respectively. These unusual effects of a strong deformation of composite on its magnetization processes were discussed in terms of the particle rearrangements in the chains.

Elastic Behavior of Transversely Isotropic Cylindrical Rock Samples under Uniaxial Compression Considering Ideal and Frictional Boundary Conditions

Conceptualizing sophisticated measurement set-ups as well as testing and evaluation procedures for laboratory experiments on anisotropic rocks requires a basic understanding of the potential specimen behavior. The focus of the present work was therefore to investigate the influence of different transversely isotropic parameters and their ratios on the elastic behavior of cylindrical rock samples in uniaxial compression tests. Parameter sets corresponding to soft anisotropic rocks were chosen based on naturally observed ranges for the five elastic transversely isotropic constants. Analytical results for the radial and vertical strain distributions around the sample circumference and a comparison with finite element simulations are presented. Further, the effect of interface friction between samples and loading platens was analyzed within the numerical models. The results suggest that radial strains around cylindrical anisotropic samples are rarely uniform except for specific combinations of parameters and isotropy plane inclinations. The effect of interface friction was found to have a clear influence on the developing elastic stress and strain distributions for samples with inclined isotropy planes. Nevertheless, no significant influence of frictional boundary conditions on the back-calibrated values of the elastic parameters could be identified, suggesting that friction-reducing measures in uniaxial compression tests on transversely isotropic samples with predominantly linear behavior are not required.

Magnetorheological effect and sensing performance of graphite sheet filled PDMS based magnetorheological elastomer under compression

In order to study the effect of large-sized graphite (Gr) sheet on the magnetorheological (MR) effect and sensing characteristics of MR elastomer (MRE), isotropic and anisotropic Gr-filled MRE samples with different carbonyl iron powder (CIP) contents were fabricated. The effect of Gr sheet on the microstructure, MR effect and sensing characteristics of the MRE samples were experimentally tested, and the mechanisms behind discussed. The results show that in the anisotropic MRE samples, the addition of Gr sheets results in the short particle chains formed between Gr sheets, thus leading to the high MR effect and low resistivity than those of isotropic counterparts. The non-monotonic resistivity responses of the Gr-filled MRE samples during compression were observed owing to the interlayer separation of Gr sheets and the reconstruction of conductive network. A higher piezoresistive response was observed from the isotropic Gr-filled MRE sample filled with the CIP content below the percolation threshold. The resistivities of the Gr-filled MRE samples decline with increasing the applied magnetic field. The isotropic sample filled with lower CIP content shows the higher magnetoresistive effect from the view point of absolute change in resistivity. While for the relative change in resistivity, the anisotropic sample filled with the higher CIP content has the higher magnetoresistive effect.

Azimuth Angle Dependence of Polarized Infrared Spectra of Injection-Molded Polyoxymethylene.

Injection-molded polyoxymethylene (POM) has molecular chains mainly oriented in the injection direction. We investigated the directional dependence of the polarized infrared reflection and attenuated total reflection spectra by rotating the anisotropic POM sample. Because of the strong absorption and large frequency dispersion of the C-O vibration in the main-chain direction, we found phenomena such as shoulder wing generation that resulted from the mixing of optical responses attributed to the vibration in the main chain and that in the direction perpendicular to the main chain. The spectra of the directional dependence can be explained qualitatively because of the anisotropy of the mode with large frequency dispersion.

Deep learning and correlative microscopy for quantification of grain orientation in sintered FeNdB-type permanent magnets by domain pattern analysis

Based on a data-driven approach, a computer-assisted workflow for the quantitative analysis of optical Kerr microscopy images of sintered FeNdB-type permanent magnets was developed. By analyzing the domain patterns visible in the Kerr image with data-driven approaches such as traditional machine learning and advanced deep learning, we can quantify grain orientation and size with a better trade-off between accuracy and higher throughput than electron backscatter diffraction (EBSD). The key distinction between traditional machine learning and advanced deep learning lies in feature extraction. Traditional methods require manual, user-dependent feature extraction from input data, while advanced deep learning achieves this automatically. The predictions from the trained models were compared to the measurements from EBSD for performance evaluation. The proposed data-driven model is trained on the dataset created from the correlative microscopy technique, which requires the images of grains extracted from the Kerr microscopy and corresponding EBSD grain orientation data (Euler angles). The fine-tuned deep learning model shows better generalization ability than the traditional machine learning models trained on the manually extracted features and resulted in a mean absolute error of less than 5° for grain orientation of the anisotropic magnet samples when evaluated against the measured EBSD values. The developed approach has reduced the measurement effort for grain orientation by 5 times and have sufficient accuracy when compared to the EBSD.Further, the application of the proposed approach to determine the quality of the alignment or texture in anisotropic sintered magnets and its relationship with the magnetic remanence based on reliable statistical grain orientation data has been discussed. This approach could emerge as a tool for rapidly analyzing large-scale samples to discover and quantify heterogeneities in grain size and grain orientation.

Inductive and magnetorheological properties of soft and hard magnetic fillers in elastomers

Magnetorheological elastomers are smart materials, that have great potential for many technical applications like intelligent semi-active dampers or energy harvesting applications. We investigate soft- and hard-magnetic filler types in typical technical elastomers under cyclic deformation regarding their influence on the electromagnetic induction and magnetic switching-ability of the compounds. The effect of vulcanization in an external magnetic field is considered leading to anisotropic samples with aligned filler particles. It is found that the soft magnetic fillers show a higher switching-ability compared to hard magnetic fillers in anisotropic samples, which is related to hysteretic and slow magnetization behaviour of hard magnetic fillers. This also leads to a negative switching effect or softening of the samples if the direction of the magnetic field is opposite to that during vulcanization, suggesting rotational motion of the particles in dependence of the outer field. The stress values and mechanical hysteresis are generally higher for the anisotropic samples, both for soft and hard magnetic fillers. This is found for quasistatic and dynamic excitations at different frequencies and can clearly be related to the alignment of particles. Nevertheless, the energy harvesting ability seems to be widely independent of this since no significant different inductive properties are found for isotropic and anisotropic samples. The possibility of a combined magnetorheological and energy harvesting application is discussed.

Isotropic and Anisotropic Complex Refractive Index of PEDOT:PSS.

In this work, the complex refractive indexes of seven PEDOT:PSS samples, three with isotropic behavior and four with optical anisotropy, were determined. For the anisotropic samples, the ordinary and extraordinary components of the refractive index were described. The effect of the film thickness, measurement technique and preparation method on the extinction coefficient (k) and refractive index (n) of each sample was also discussed. Important differences (up to 20% in the average n) were found among the samples investigated. In most anisotropic films, the mean value of the extraordinary component was between 7 and 10% higher than that of the ordinary. In the three isotropic films, the average k rose when the film thickness increased. Moreover, the different sets of refractive index data were fitted to three different models: the original Forouhi-Bloomer model, the Liu (2007) model and the revised version of the Forouhi-Bloomer model (2019). In general, Liu's model gave better results, with small errors in n and k (<7.81 and 4.68%, respectively, in all the cases). However, this model had seven fitting parameters, which led to significantly longer computation time than the other two models. The influence of the differences in the measurement of the complex refractive index on the simulation of the optical properties of PEDOT:PSS multilayers was discussed. The results showed that n must be known precisely to accurately calculate the light absorption in a multilayer, without ignoring the isotropic or anisotropic behavior of the material or the influence of the layer thickness on its optical properties. This study aids in the development of simulation and optimization tools that allow understanding the optical properties of PEDOT:PSS films for their potential applications in organic optoelectronic devices, such as organic solar cells.