Journal of Composites Science

Research

21 pages, 6455 KiB

Open AccessArticle

Determination of Crack Depth in Brickworks by Ultrasonic Methods: Numerical Simulation and Regression Analysis

by Alexey N. Beskopylny, Sergey A. Stel’makh, Evgenii M. Shcherban’, Vasilii Dolgov, Irina Razveeva, Nikita Beskopylny, Diana Elshaeva and Andrei Chernil’nik

J. Compos. Sci. 2024, 8(12), 536; https://doi.org/10.3390/jcs8120536 - 16 Dec 2024

Viewed by 455

Abstract

Ultrasonic crack detection is one of the effective non-destructive methods of structural health monitoring (SHM) of buildings and structures. Despite its widespread use, crack detection in porous and heterogeneous composite building materials is an insufficiently studied issue and in practice leads to significant [...] Read more.

Ultrasonic crack detection is one of the effective non-destructive methods of structural health monitoring (SHM) of buildings and structures. Despite its widespread use, crack detection in porous and heterogeneous composite building materials is an insufficiently studied issue and in practice leads to significant errors of more than 40%. The purpose of this article is to study the processes occurring in ceramic bricks weakened by cracks under ultrasonic exposure and to develop a method for determining the crack depth based on the characteristics of the obtained ultrasonic response. At the first stage, the interaction of the ultrasonic signal with the crack and the features of the pulse propagation process in ceramic bricks were considered using numerical modeling with the ANSYS environment. The FEM model allowed us to identify the characteristic aspects of wave propagation in bricks and compare the solution with the experimental one for the reference sample. Further experimental studies were carried out on ceramic bricks, as the most common elements of buildings and structures. A total of 110 bricks with different properties were selected. The cracks were natural or artificially created and were of varying depth and width. The experimental data showed that the greatest influence on the formation of the signal was exerted by the time parameters of the response: the time when the signal reaches a value of 12 units, the time of reaching the first maximum, the time of reaching the first minimum, and the properties of the material. Based on the regression analysis, a model was obtained that relates the crack depth to the signal parameters and the properties of the material. The error in the predicted values according to this model was approximately 8%, which was significantly more accurate than the existing approach. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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28 pages, 13426 KiB

Open AccessArticle

Phase Field Modelling of Failure in Thermoset Composites Under Cure-Induced Residual Stress

by Aravind Balaji, David Dumas and Olivier Pierard

J. Compos. Sci. 2024, 8(12), 533; https://doi.org/10.3390/jcs8120533 - 15 Dec 2024

Viewed by 500

Abstract

This study examines the residual stress induced by manufacturing and its effect on failure in thermosetting unidirectional composites under quasi-static loading, using Finite Element-based computational models. During the curing process, the composite material develops residual stress fields due to various phenomena. These stress [...] Read more.

This study examines the residual stress induced by manufacturing and its effect on failure in thermosetting unidirectional composites under quasi-static loading, using Finite Element-based computational models. During the curing process, the composite material develops residual stress fields due to various phenomena. These stress fields are predicted using a constitutive viscoelastic model and subsequently initialized within a damage-driven Phase Field model. Structural tensors are used to modify the stress-based failure criteria to account for inherent transverse isotropy. This influence is incorporated into the crack phase field evolution equation, enabling a modular framework that retains all residual stress information through a heat-transfer analogy. The proposed coupled computational model is validated through a representative numerical case study involving L-shaped composite parts. The findings reveal that cure-induced residual stresses, in conjunction with discontinuities, play a critical role in matrix cracking and significantly affect the structural load-carrying capacity. The proposed coupled numerical approach provides an initial estimation of the influence of manufacturing defects and streamlines the optimization of cure profiles to enhance manufacturing quality. Among the investigated curing strategies, the three-dwell cure cycle emerged as the most effective solution. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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24 pages, 4046 KiB

Open AccessArticle

A Unified Shear Deformation Theory for Piezoelectric Beams with Geometric Nonlinearities—Analytical Modelling and Bending Analysis

by Konstantinos I. Ntaflos, Konstantinos G. Beltsios and Evangelos P. Hadjigeorgiou

J. Compos. Sci. 2024, 8(12), 494; https://doi.org/10.3390/jcs8120494 - 26 Nov 2024

Viewed by 493

Abstract

The objective of the present paper is to demonstrate the effects of shear deformation and large deflections on the piezoelectric materials and structures which often serve as substrate layers of multilayer composite sensors and actuators. Based on a displacement-unified high-order shear deformation theory [...] Read more.

The objective of the present paper is to demonstrate the effects of shear deformation and large deflections on the piezoelectric materials and structures which often serve as substrate layers of multilayer composite sensors and actuators. Based on a displacement-unified high-order shear deformation theory and the von Kármán geometric nonlinearity, a general theory (governing equations and associated boundary conditions) for the analysis of piezoelectric beams is developed using Hamilton’s principle. Nonlinear effects due to the coupling between extensional and bending responses in beams with moderately large rotations but small strains are included. A bending problem for a piezoelectric beam is solved analytically, and the obtained results are compared to the results available in the literature. The numerical results show that both shear deformation effects and von Kármán geometric nonlinearity have a stiffening effect and therefore reduce the displacements. The influence of geometric nonlinearity is more prominent in the case of thin beams, while the effects of shear deformation dominate in the case of thick beams. The proposed unified methodology for the analysis of bending problems is independent of the thickness of the piezoelectric beam. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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13 pages, 7087 KiB

Open AccessArticle

Numerical Analysis on Static Performances of Graphene Platelet-Reinforced Ethylene-Tetrafluoroethylene (ETFE) Composite Membrane Under Wind Loading

by Yu Wang, Jiajun Gu, Xin Zhang, Jian Fan, Wenbin Ji and Chuang Feng

J. Compos. Sci. 2024, 8(11), 478; https://doi.org/10.3390/jcs8110478 - 18 Nov 2024

Viewed by 388

Abstract

This study examines the static performances of a graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) composite membrane under wind loadings. The wind pressure distribution on a periodic tensile membrane unit was analyzed by using CFD simulations, which considered various wind velocities and directions. A [...] Read more.

This study examines the static performances of a graphene platelet (GPL)-reinforced ethylene tetrafluoroethylene (ETFE) composite membrane under wind loadings. The wind pressure distribution on a periodic tensile membrane unit was analyzed by using CFD simulations, which considered various wind velocities and directions. A one-way fluid–structure interaction (FSI) analysis incorporating geometric nonlinearity was performed in ANSYS to evaluate the static performances of the composite membrane. The novelty of this research lies in the integration of graphene platelets (GPLs) into ETFE membranes to enhance their static performance under wind loading and the combination of micromechanical modelling for obtaining material properties of the composites and finite element simulation for examining structural behaviors, which is not commonly explored in the existing literature. The elastic properties required for the structural analysis were determined using effective medium theory (EMT), while Poisson’s ratio and mass density were evaluated using rule of mixtures. Parametric studies were carried out to explore the effects of a number of influencing factors, including pre-strain, attributes of wind, and GPL reinforcement. It is demonstrated that higher initial strain effectively reduced deformation under wind loads at the cost of increased stress level. The deformation and stress significantly increased with the increase in wind velocity. The deflection and stress level vary with the wind direction, and the maximum values were observed when the wind comes at 15° and 45°, respectively. Introducing GPLs with a larger surface area into membrane material has proven to be an effective way to control membrane deformation, though it also results in a higher stress level, indicating a trade-off between deformation management and stress management. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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15 pages, 1393 KiB

Open AccessArticle

The Impact of Activated Carbon–Me_xO_y (Me = Bi, Mo, Zn) Additives on the Thermal Decomposition Kinetics of the Ammonium Nitrate–Magnesium–Nitrocellulose Composite

by Zhanerke Yelemessova, Ayan Yerken, Dana Zhaxlykova and Bagdatgul Milikhat

J. Compos. Sci. 2024, 8(10), 420; https://doi.org/10.3390/jcs8100420 - 12 Oct 2024

Viewed by 886

Abstract

This research investigates the impact of additives such as activated carbon (AC) combined with metal oxides (Bi₂O₃, MoO₃, and ZnO) on the thermal decomposition kinetics of ammonium nitrate (AN), magnesium (Mg), and nitrocellulose (NC) as a basic [...] Read more.

This research investigates the impact of additives such as activated carbon (AC) combined with metal oxides (Bi₂O₃, MoO₃, and ZnO) on the thermal decomposition kinetics of ammonium nitrate (AN), magnesium (Mg), and nitrocellulose (NC) as a basic AN–Mg–NC composite. To study the thermal properties of the AN–Mg–NC composite with and without the AC–Me_xO_y (Me = Bi, Mo, Zn) additive, a differential scanning calorimetry (DSC) analysis was conducted. The DSC results show that the AC–Me_xO_y (Me = Bi, Mo, Zn) additive catalytically affects the basic AN–Mg–NC composite, lowering the peak decomposition temperature (T_max) from 534.58 K (AN–Mg–NC) to 490.15 K (with the addition of AC), 490.76 K (with AC–Bi₂O₃), 492.17 K (with AC–MoO₃), and 492.38 K (with AC–ZnO) at a heating rate of β equal to 5 K/min. Based on the DSC data, the activation energies (E_a) for the AN–Mg–NC, AN–Mg–NC–AC, and AN–Mg–NC–AC–Me_xO_y (Me = Bi, Mo, Zn) composites were determined using the Kissinger method. The results suggest that incorporating AC and AC–Me_xO_y (Me = Bi, Mo, Zn) additives reduce the decomposition temperatures and activation energies of the basic AN–Mg–NC composite. Specifically, E_a decreased from 99.02 kJ/mol (for AN–Mg–NC) to 93.63 kJ/mol (with addition of AC), 91.45 kJ/mol (with AC–Bi₂O₃), 91.65 kJ/mol (with AC–MoO₃), and 91.76 kJ/mol (with AC–ZnO). These findings underscore the potential of using AC–Me_xO_y (Me = Bi, Mo, Zn) as a catalytic additive to enhance the performance of AN–Mg–NC-based energetic materials, increasing their efficiency and reliability for use in solid propellants. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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22 pages, 5451 KiB

Open AccessArticle

Synthesis of a New Composite Material Derived from Cherry Stones and Sodium Alginate—Application to the Adsorption of Methylene Blue from Aqueous Solution: Process Parameter Optimization, Kinetic Study, Equilibrium Isotherms, and Reusability

by Cristina-Gabriela Grigoraș and Andrei-Ionuț Simion

J. Compos. Sci. 2024, 8(10), 402; https://doi.org/10.3390/jcs8100402 - 3 Oct 2024

Viewed by 835

Abstract

Purifying polluted water is becoming a crucial concern to meet quantity and quality demands as well as to ensure the resource’s sustainability. In this study, a new material was prepared from cherry stone powder and sodium alginate, and its capacity to remove methylene [...] Read more.

Purifying polluted water is becoming a crucial concern to meet quantity and quality demands as well as to ensure the resource’s sustainability. In this study, a new material was prepared from cherry stone powder and sodium alginate, and its capacity to remove methylene blue (MB) from water was determined. The characterization of the resulting product, performed via scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), revealed that the raw material considered for the synthesis was successfully embedded in the polymeric matrix. The impact of three of the main working parameters (pH 3–9, adsorbent dose 50–150 g/L, contact time 60–180 min) on the retention of MB was evaluated through response surface methodology with a Box–Behnken design. In the optimal settings, a removal efficiency of 80.46% and a maximum sorption capacity of 0.3552 mg/g were recorded. MB retention followed the pseudo-second-order kinetic and was suitably described by Freundlich, Khan, Redlich–Peterson, and Sips isotherm models. The experimental results show that the synthesized composite can be used for at least three successive cycles of MB adsorption. From these findings, it can be concluded that the use of the cherry-stone-based adsorbent is environmentally friendly, and efficacious in the removal of contaminants from the water environment. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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13 pages, 2347 KiB

Open AccessArticle

Nitrogen-Doped Borophene Quantum Dots: A Novel Sensing Material for the Detection of Hazardous Environmental Gases

by Kriengkri Timsorn and Chatchawal Wongchoosuk

J. Compos. Sci. 2024, 8(10), 397; https://doi.org/10.3390/jcs8100397 - 1 Oct 2024

Viewed by 1244

Abstract

Toxic gases emitted by industries and vehicles cause environmental pollution and pose significant health risks which are becoming increasingly dangerous. Therefore, the detection of the toxic gases is crucial. The development of gas sensors with high sensitivity and fast response based on nanomaterials [...] Read more.

Toxic gases emitted by industries and vehicles cause environmental pollution and pose significant health risks which are becoming increasingly dangerous. Therefore, the detection of the toxic gases is crucial. The development of gas sensors with high sensitivity and fast response based on nanomaterials has garnered significant interest. In this work, we studied the adsorption behavior of

{B_{9}}^{-}

wheel structures of pristine and nitrogen functionalized borophene quantum dots for major hazardous environmental gases, such as NO₂, CO₂, CO, and NH₃. The self-consistent-charge density-functional tight-binding method (SCC-DFTB) method was performed to investigate structural geometries, the most favorable adsorption sites, charge transfer, total densities of states, and electronic properties of the structures before and after adsorption of the gas molecules. Based on calculated results, it was found that the interaction between the borophene quantum dots and the gas molecules was chemisorption. The functionalized nitrogen atom contributed to impurity states, leading to higher adsorption energies of the functionalized borophene quantum dots compared to the pristine ones. Total densities of states revealed insights into electronic properties of gas molecules adsorbed on borophene quantum dots. The nitrogen-doped borophene quantum dots demonstrated excellent performance as a sensing material for hazardous environmental gases, especially CO₂. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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18 pages, 1565 KiB

Open AccessArticle

Design of an Overhead Crane in Steel, Aluminium and Composite Material Using the Prestress Method

by Luigi Solazzi and Ivan Tomasi

J. Compos. Sci. 2024, 8(9), 380; https://doi.org/10.3390/jcs8090380 - 23 Sep 2024

Viewed by 835

Abstract

The present research describes a design of an overhead crane using different materials with a prestress method, which corresponds to an external compression force with the aim of reducing the displacement of the beam due to the external load. This study concerns a [...] Read more.

The present research describes a design of an overhead crane using different materials with a prestress method, which corresponds to an external compression force with the aim of reducing the displacement of the beam due to the external load. This study concerns a bridge crane with a span length of 10 m, with a payload equal to 20,000 N and an estimated fatigue life of 50,000 cycles. Three different materials are studied: steel S355JR, aluminium alloy 6061-T6 and carbon fibre-reinforced polymer (CFRP). These materials are analysed with and without the contribution of the prestress method. In reference to the prestressed steel solution (which has a weight equal to 79% of the non-prestressed configuration), this study designed an aluminium solution that is 50.7% of the weight of the steel one and a composite solution that is always 20.3% of the steel configuration. In combining the methods, i.e., the materials and prestress, compared to the non-prestressed steel solution with a weight evaluated to be 758 kg, the weight of the aluminium configuration is equal to 40% of the traditional one, and the composite value is reduced to 16%, with a weight of 121 kg. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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17 pages, 4548 KiB

Open AccessArticle

Fracture Behavior of Crack-Damaged Concrete Beams Reinforced with Ultra-High-Performance Concrete Layers

by Zenghui Guo, Xuejun Tao, Zhengwei Xiao, Hui Chen, Xixi Li and Jianlin Luo

J. Compos. Sci. 2024, 8(9), 355; https://doi.org/10.3390/jcs8090355 - 10 Sep 2024

Viewed by 1218

Abstract

Reinforcing crack-damaged concrete structures with ultra-high-performance concrete (UHPC) proves to be more time-, labor-, and cost-efficient than demolishing and rebuilding under the dual-carbon strategy. In this study, the extended finite element method (XFEM) in ABAQUS was first employed to develop a numerical model [...] Read more.

Reinforcing crack-damaged concrete structures with ultra-high-performance concrete (UHPC) proves to be more time-, labor-, and cost-efficient than demolishing and rebuilding under the dual-carbon strategy. In this study, the extended finite element method (XFEM) in ABAQUS was first employed to develop a numerical model of UHPC-reinforced single-notched concrete (U+SNC) beams, analyze their crack extension behavior, and obtain the parameters necessary for calculating fracture toughness. Subsequently, the fracture toughness and instability toughness of U+SNC were calculated using the improved double K fracture criterion. The effects of varying crack height ratios (a/h) of SNC, layer thicknesses (d) of UHPC reinforcement, and fiber contents in UHPC (V_SF) on the fracture properties of U+SNC beams were comprehensively investigated. The results indicate that (1) the UHPC reinforcement layer significantly enhances the load-carrying capacity and crack resistance of the U+SNC beams. Crack extension in the reinforced beams occurs more slowly than in the unreinforced beams; |(2) the fracture performance of the U+BNC beams increases exponentially with d. Considering both the reinforcement effect benefit and beam deadweight, the optimal cost-effective performance is achieved when d is 20 mm; (3) with constant d, increasing a/h favors the reinforcement effect of UHPC on the beams; (4) as V_SF increases, the crack extension stage in the U+BNC beam becomes more gradual, with higher toughness and flexural properties; therefore, the best mechanical properties are achieved at a V_SF of 3%. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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13 pages, 3582 KiB

Open AccessArticle

Shear Behavior and Modeling of Short Glass Fiber- and Talc-Filled Recycled Polypropylene Composites at Different Operating Temperatures

by Andrea Iadarola, Pietro Di Matteo, Raffaele Ciardiello, Francesco Gazza, Vito Guido Lambertini, Valentina Brunella and Davide Salvatore Paolino

J. Compos. Sci. 2024, 8(9), 345; https://doi.org/10.3390/jcs8090345 - 3 Sep 2024

Viewed by 936

Abstract

The present paper aims to broaden the field of application of the phenomenological model proposed by the authors in a previous study (ICP model) and to assess the shear properties of a recycled 30 wt.% talc-filled polypropylene (TFPP) and a recycled 30 wt.% [...] Read more.

The present paper aims to broaden the field of application of the phenomenological model proposed by the authors in a previous study (ICP model) and to assess the shear properties of a recycled 30 wt.% talc-filled polypropylene (TFPP) and a recycled 30 wt.% short glass fiber-reinforced polypropylene (SGFPP), used in the automotive industry. The materials were produced by injection molding employing post-industrial mechanical shredding of recycled materials. In particular, Iosipescu shear tests adopting the American Standard for Testing Materials (ASTM D5379) at three different operating temperatures (−40, 23 and 85 °C) were performed. The strain was acquired using a Digital Image Correlation (DIC) system to determine the map of the strain in the area of interest before failure. Lower operating temperatures led to higher shear chord moduli and higher strengths. Recycled SGFPP material showed higher mechanical properties and smaller strains at failure with respect to recycled TFPP. Finally, the ICP model also proved to be suitable and accurate for the prediction of the shear behavior of 30 wt.% SGFPP and 30 wt.% TFPP across different operating temperatures. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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12 pages, 3722 KiB

Open AccessArticle

Mechanical and Physical Characteristics of Oil Palm Empty Fruit Bunch as Fine Aggregate Replacement in Ordinary Portland Cement Mortar Composites

by Sotya Astutiningsih, Rahmat Zakiy Ashma’, Hammam Harits Syihabuddin, Evawani Ellisa and Muhammad Saukani

J. Compos. Sci. 2024, 8(9), 341; https://doi.org/10.3390/jcs8090341 - 30 Aug 2024

Viewed by 724

Abstract

Palm oil empty fruit bunch (OEB) is the largest source of waste in the production of crude palm oil. Utilizing this waste in various applications can help reduce its volume and mitigate adverse environmental effects. In this study, fibers from OEB without any [...] Read more.

Palm oil empty fruit bunch (OEB) is the largest source of waste in the production of crude palm oil. Utilizing this waste in various applications can help reduce its volume and mitigate adverse environmental effects. In this study, fibers from OEB without any chemical treatment are introduced into Ordinary Portland Cement (OPC)-based mortar to partially replace fine aggregates, aiming to reduce the mortar’s density. The goal of this experimental study is to observe the mechanical and physical performance of the samples according to the effect of the addition of OEB. The composite samples were made by replacing 1%, 2%, and 3% of the weight of quartz sand as the fine aggregate with OEB (fine and coarse). The hardened composites were further tested to determine their compressive strength, and it was found that the replacement of sand with OEB led to a decrease in compressive strength and flowability while alleviating the mortar’s density and affecting the setting time. The decrease in compressive strength was attributed to cavities present in the samples. Flexural tests and 28-day drying shrinkage measurements were carried out on the samples with 1% replacement of sand with OEB. The experiments showed that OEB fibers increased the flexural strength, functioned as a crack barrier, and reduced drying shrinkage. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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23 pages, 7759 KiB

Open AccessArticle

Machine Learning Algorithms for Prediction and Characterization of Cohesive Zone Parameters for Mixed-Mode Fracture

by Arash Ramian and Rani Elhajjar

J. Compos. Sci. 2024, 8(8), 326; https://doi.org/10.3390/jcs8080326 - 17 Aug 2024

Viewed by 924

Abstract

Fatigue and fracture prediction in composite materials using cohesive zone models depends on accurately characterizing the core and facesheet interface in advanced composite sandwich structures. This study investigates the use of machine learning algorithms to identify cohesive zone parameters used in the fracture [...] Read more.

Fatigue and fracture prediction in composite materials using cohesive zone models depends on accurately characterizing the core and facesheet interface in advanced composite sandwich structures. This study investigates the use of machine learning algorithms to identify cohesive zone parameters used in the fracture analysis of advanced composite sandwich structures. Experimental results often yield non-unique solutions, complicating the determination of cohesive parameters. Numerical determination can be time-consuming due to fine mesh requirements near the crack tip. This research evaluates the performance of Support Vector Regression (SVR), Random Forest (RF), and Artificial Neural Network (ANN) machine learning methods. The study uses features extracted from load–displacement responses during the fracture of the Asymmetric Double-Cantilever Beam (ADCB) specimen. The inputs include the displacement at the maximum load (δ*), the maximum load (

P_{m a x}

), the total area under the load–displacement curve (

A_{t}

), and the initial slope of the linear region of the load–displacement curve (m). There are two objectives in this research: the first is to investigate which method performs best in identifying the interfacial cohesive parameters between the honeycomb core and carbon-epoxy facesheets, while the second objective is to reduce the dimensionality of the dataset by reducing the number of input features. Reducing the number of inputs can simplify the models and potentially improve the performance and interpretability. The results show that the ANN method produced the best results, with a mean absolute percentage error (MAPE) of 0.9578% and an R-squared (R²) value of 0.7932. These values indicate a high level of accuracy in predicting the four cohesive zone parameters: maximum normal contact stress (

σ_{I}

), critical fracture energy for normal separation (

G_{I}

), maximum equivalent tangential contact stress (

σ_{I I}

), and critical fracture energy for tangential slip (

G_{I I}

). Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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17 pages, 3847 KiB

Open AccessArticle

Molecular Dynamics Simulations of Effects of Geometric Parameters and Temperature on Mechanical Properties of Single-Walled Carbon Nanotubes

by Lida Najmi and Zhong Hu

J. Compos. Sci. 2024, 8(8), 293; https://doi.org/10.3390/jcs8080293 - 30 Jul 2024

Viewed by 1029

Abstract

Carbon nanotubes (CNTs) are considered an advanced form of carbon. They have superior characteristics in terms of mechanical and thermal properties compared to other available fibers and can be used in various applications, such as supercapacitors, sensors, and artificial muscles. The properties of [...] Read more.

Carbon nanotubes (CNTs) are considered an advanced form of carbon. They have superior characteristics in terms of mechanical and thermal properties compared to other available fibers and can be used in various applications, such as supercapacitors, sensors, and artificial muscles. The properties of single-walled carbon nanotubes (SWNTs) are significantly affected by geometric parameters such as chirality and aspect ratio, and testing conditions such as temperature and strain rate. In this study, the effects of geometric parameters and temperature on the mechanical properties of SWNTs were studied by molecular dynamics (MD) simulations using the Large-scaled Atomic/Molecular Massively Parallel Simulator (LAMMPS). Based on the second-generation reactive empirical bond order (REBO) potential, SWNTs of different diameters were tested in tension and compression under different strain rates and temperatures to understand their effects on the mechanical behavior of SWNTs. It was observed that the Young’s modulus and the tensile strength decreases with increasing SWNT tube diameter. As the chiral angle increases, the tensile strength increases, while the Young’s modulus decreases. The simulations were repeated at different temperatures of 300 K, 900 K, 1500 K, 2100 K and different strain rates of 1 × 10⁻³/ps, 0.75 × 10⁻³/ps, 0.5 × 10⁻³/ps, and 0.25 × 10⁻³/ps to investigate the effects of temperature and strain rate, respectively. The results show that the ultimate tensile strength of SWNTs increases with increasing strain rate. It is also seen that when SWNTs were stretched at higher temperatures, they failed at lower stresses and strains. The compressive behavior results indicate that SWNTs tend to buckle under lower stresses and strains than those under tensile stress. The simulation results were validated by and consistent with previous studies. The presented approach can be applied to investigate the properties of other advanced materials. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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10 pages, 3234 KiB

Open AccessArticle

Ab Initio Modelling of g-ZnO Deposition on the Si (111) Surface

by Aliya Alzhanova, Yuri Mastrikov and Darkhan Yerezhep

J. Compos. Sci. 2024, 8(7), 281; https://doi.org/10.3390/jcs8070281 - 20 Jul 2024

Viewed by 706

Abstract

Recent studies show that zinc oxide (ZnO) nanostructures have promising potential as an absorbing material. In order to improve the optoelectronic properties of the initial system, this paper considers the process of adsorbing multilayer graphene-like ZnO onto a Si (111) surface. The density [...] Read more.

Recent studies show that zinc oxide (ZnO) nanostructures have promising potential as an absorbing material. In order to improve the optoelectronic properties of the initial system, this paper considers the process of adsorbing multilayer graphene-like ZnO onto a Si (111) surface. The density of electron states for two- and three-layer graphene-like zinc oxide on the Si (111) surface was obtained using the Vienna ab-initio simulation package by the DFT method. A computer model of graphene-like Zinc oxide on a Si (111)-surface was created using the DFT+U approach. One-, two- and three-plane-thick graphene-zinc oxide were deposited on the substrate. An isolated cluster of Zn₃O₃ was also considered. The compatibility of g-ZnO with the S (100) substrate was tested, and the energetics of deposition were calculated. This study demonstrates that, regardless of the possible configuration of the adsorbing layers, the Si/ZnO structure remains stable at the interface. Calculations indicate that, in combination with lower formation energies, wurtzite-type structures turn out to be more stable and, compared to sphalerite-type structures, wurtzite-type structures form longer interlayers and shorter interplanar distances. It has been shown that during the deposition of the third layer, the growth of a wurtzite-type structure becomes exothermic. Thus, these findings suggest a predictable relationship between the application method and the number of layers, implying that the synthesis process can be modified. Consequently, we believe that such interfaces can be obtained through experimental synthesis. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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13 pages, 4505 KiB

Open AccessArticle

Multiscale Modeling of Elastic Waves in Carbon-Nanotube-Based Composite Membranes

by Elaf N. Mahrous, Muhammad A. Hawwa, Abba A. Abubakar and Hussain M. Al-Qahtani

J. Compos. Sci. 2024, 8(7), 258; https://doi.org/10.3390/jcs8070258 - 3 Jul 2024

Viewed by 811

Abstract

A multiscale model is developed for vertically aligned carbon nanotube (CNT)-based membranes that are made for water purification or gas separation. As a consequence of driving fluids through the membranes, they carry stress waves along the fiber direction. Hence, a continuum mixture theory [...] Read more.

A multiscale model is developed for vertically aligned carbon nanotube (CNT)-based membranes that are made for water purification or gas separation. As a consequence of driving fluids through the membranes, they carry stress waves along the fiber direction. Hence, a continuum mixture theory is established for a representative volume element to characterize guided waves propagating in a periodically CNT-reinforced matrix material. The obtained coupled governing equations for the CNT-based composite are found to retain the integrity of the wave propagation phenomenon in each constituent, while allowing them to coexist under analytically derived multiscale interaction parameters. The influence of the mesoscale characteristics on the continuum behavior of the composite is demonstrated by dispersion curves of harmonic wave propagation. Analytically established continuum mixture theory for the CNT-based composite is strengthened by numerical simulations conducted in COMSOL for visualizing mode shapes and wave propagation patterns. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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19 pages, 3964 KiB

Open AccessArticle

A Design Optimization Study of Step/Scarf Composite Panel Repairs, Targeting the Maximum Strength and the Minimization of Material Removal

by Spyridon Psarras, Maria-Panagiota Giannoutsou and Vassilis Kostopoulos

J. Compos. Sci. 2024, 8(7), 248; https://doi.org/10.3390/jcs8070248 - 30 Jun 2024

Viewed by 775

Abstract

This study aimed to optimize the geometry of composite stepped repair patches, using a parametric algorithm to automate the process due to the complexity of the optimization problem and various factors affecting efficiency. More specifically, the algorithm initially calculates the equivalent strengths of [...] Read more.

This study aimed to optimize the geometry of composite stepped repair patches, using a parametric algorithm to automate the process due to the complexity of the optimization problem and various factors affecting efficiency. More specifically, the algorithm initially calculates the equivalent strengths of the repaired laminate plate according to a max stress criterion, then calculates the dimensions of several elliptical repair patches, taking into account several design methods extracted from the literature. Next, it creates their finite element models and finally, the code conducts an assessment of the examined patch geometries, given specific user-defined criteria. In the end, the algorithm reaches a conclusion about the optimum patch among the designed ones. The algorithm has the potential to run for many different patch geometries. In the current research, five patch geometries were designed and modeled under uniaxial compressive loading at 0°, 45° and 90°. Overall, the code greatly facilitated the design and optimization process and constitutes a useful tool for future research. The results revealed that elliptical stepped patches can offer a near-optimum solution much more efficient than that of the conservative option of the circular patch, in terms of both strength and volume of healthy removed material. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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14 pages, 2486 KiB

Open AccessArticle

Thermomechanical Responses and Energy Conversion Efficiency of a Hybrid Thermoelectric–Piezoelectric Layered Structure

by Zhihe Jin and Jiashi Yang

J. Compos. Sci. 2024, 8(5), 171; https://doi.org/10.3390/jcs8050171 - 6 May 2024

Viewed by 1182

Abstract

This paper develops a thermoelectric (TE)–piezoelectric (PE) hybrid structure with the PE layer acting as both a support membrane and a sensor for the TE film for microelectronics applications. The TE and PE layers are assumed to be perfectly bonded mechanically and thermally [...] Read more.

This paper develops a thermoelectric (TE)–piezoelectric (PE) hybrid structure with the PE layer acting as both a support membrane and a sensor for the TE film for microelectronics applications. The TE and PE layers are assumed to be perfectly bonded mechanically and thermally but electrically shielded and insulated with each other. The thermo-electro-mechanical responses of the hybrid bilayer under the TE generator operation conditions are obtained, and the influence of the PE layer on the TE energy conversion efficiency is investigated. The numerical results for a Bi₂Te₃/PZT-5H bilayer structure show that large compressive stresses develop in both the PE and TE layers. With a decrease in the PE layer thickness, the magnitude of the maximum compressive stress in the PE layer increases whereas the maximum magnitude of the stress in the TE layer decreases. The numerical result of the TE energy conversion efficiency shows that increasing the PE layer thickness leads to lower energy conversion efficiencies. A nearly 40% reduction in the peak efficiency is observed with a PE layer of the same thickness as that of the TE layer. These results suggest that design of TE films with supporting/sensing membranes must consider both aspects of energy conversion efficiency and the thermomechanical reliability of both the TE and PE layers. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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26 pages, 5545 KiB

Open AccessArticle

Simulation of the Dynamic Responses of Layered Polymer Composites under Plate Impact Using the DSGZ Model

by Huadian Zhang, Arunachalam M. Rajendran, Manoj K. Shukla, Sasan Nouranian, Ahmed Al-Ostaz, Steven Larson and Shan Jiang

J. Compos. Sci. 2024, 8(5), 159; https://doi.org/10.3390/jcs8050159 - 23 Apr 2024

Viewed by 1772

Abstract

This paper presents a numerical study on the dynamic response and impact mitigation capabilities of layered ceramic–polymer–metal (CPM) composites under plate impact loading, focusing on the layer sequence effect. The layered structure, comprising a ceramic for hardness and thermal resistance, a polymer for [...] Read more.

This paper presents a numerical study on the dynamic response and impact mitigation capabilities of layered ceramic–polymer–metal (CPM) composites under plate impact loading, focusing on the layer sequence effect. The layered structure, comprising a ceramic for hardness and thermal resistance, a polymer for energy absorption, and a metal for strength and ductility, is analyzed to evaluate its effectiveness in mitigating the impact loading. The simulations employed the VUMAT subroutine of DSGZ material models within Abaqus/Explicit to accurately represent the mechanical behavior of the polymeric materials in the composites. The VUMAT implementation incorporates the explicit time integration scheme and the implicit radial return mapping algorithm. A safe-version Newton–Raphson method is applied for numerically solving the differential equations of the

J_{2}

plastic flow theory. Analysis of the simulation results reveals that specific layer configurations significantly influence wave propagation, leading to variations in energy absorption and stress distribution within the material. Notably, certain layer sequences, such as P-C-M and C-P-M, exhibit enhanced impact mitigation with a superior ability to dissipate and redirect the impact energy. This phenomenon is tied to the interactions between the material properties of the ceramic, polymer, and metal, emphasizing the necessity of precise material characterization and enhanced understanding of the layer sequencing effect for optimizing composite designs for impact mitigation. The integration of empirical data with simulation methods provides a comprehensive framework for optimizing composite designs in high-impact scenarios. In the general fields of materials science and impact engineering, the current research offers some guidance for practical applications, underscoring the need for detailed simulations to capture the high-strain-rate dynamic responses of multilayered composites. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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15 pages, 2598 KiB

Open AccessArticle

Effects of Topological Parameters on Thermal Properties of Carbon Nanotubes via Molecular Dynamics Simulation

by Lida Najmi and Zhong Hu

J. Compos. Sci. 2024, 8(1), 37; https://doi.org/10.3390/jcs8010037 - 22 Jan 2024

Cited by 5 | Viewed by 2265

Abstract

Due to their unique properties, carbon nanotubes (CNTs) are finding a growing number of applications across multiple industrial sectors. These properties of CNTs are subject to influence by numerous factors, including the specific chiral structure, length, type of CNTs used, diameter, and temperature. [...] Read more.

Due to their unique properties, carbon nanotubes (CNTs) are finding a growing number of applications across multiple industrial sectors. These properties of CNTs are subject to influence by numerous factors, including the specific chiral structure, length, type of CNTs used, diameter, and temperature. In this topic, the effects of chirality, diameter, and length of single-walled carbon nanotubes (SWNTs) on the thermal properties were studied using the reverse non-equilibrium molecular dynamics (RNEMD) method and the Tersoff interatomic potential of carbon–carbon based on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). For the shorter SWNTs, the effect of chirality on the thermal conductivity is more obvious than for longer SWNTs. Thermal conductivity increases with increasing chiral angle, and armchair SWNTs have higher thermal conductivity than that of zigzag SWNTs. As the tube length becomes longer, the thermal conductivity increases while the effect of chirality on the thermal conductivity decreases. Furthermore, for SWNTs with longer lengths, the thermal conductivity of zigzag SWNTs is higher than that of the armchair SWNTs. Thermal resistance at the nanotube–nanotube interfaces, particularly the effect of CNT overlap length on thermal resistance, was studied. The simulation results were compared with and in agreement with the experimental and simulation results from the literature. The presented approach could be applied to investigate the properties of other advanced materials. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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14 pages, 3621 KiB

Open AccessArticle

First Principle Study of Structural, Electronic, Optical Properties of Co-Doped ZnO

by Ahmed Soussi, Redouane Haounati, Abderrahim Ait hssi, Mohamed Taoufiq, Abdellah Asbayou, Abdeslam Elfanaoui, Rachid Markazi, Khalid Bouabid and Ahmed Ihlal

J. Compos. Sci. 2023, 7(12), 511; https://doi.org/10.3390/jcs7120511 - 7 Dec 2023

Cited by 5 | Viewed by 2071

Abstract

In this theoretical study, the electronic, structural, and optical properties of copper-doped zinc oxide (CZO) were investigated using the full-potential linearized enhanced plane wave method (FP-LAPW) based on the density functional theory (DFT). The Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) was employed [...] Read more.

In this theoretical study, the electronic, structural, and optical properties of copper-doped zinc oxide (CZO) were investigated using the full-potential linearized enhanced plane wave method (FP-LAPW) based on the density functional theory (DFT). The Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) was employed to enhance the accuracy of the electronic structure description. The introduction of copper atoms as donors in the ZnO resulted in a reduction in the material’s band gap from 2.82 eV to 2.72 eV, indicating enhanced conductivity. This reduction was attributed to the Co-3d intra-band transitions, primarily in the spin-down configuration, leading to increased optical absorption in the visible range. The Fermi level of the pure ZnO shifted towards the conduction band, indicating metal-like characteristics in the CZO. Additionally, the CZO nanowires displayed a significant blue shift in their optical properties, suggesting a change in the energy band structure. These findings not only contribute to a deeper understanding of the CZO’s fundamental properties but also open avenues for its potential applications in optoelectronic and photonic devices, where tailored electronic and optical characteristics are crucial. This study underscores the significance of computational techniques in predicting and understanding the behavior of doped semiconductors, offering valuable insights for the design and development of novel materials for advanced electronic applications. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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14 pages, 12851 KiB

Open AccessArticle

Mechanics and Crack Analysis of Irida Graphene Bilayer Composite: A Molecular Dynamics Study

by Jianyu Li, Mingjun Han, Shuai Zhao, Teng Li, Taotao Yu, Yinghe Zhang, Ho-Kin Tang and Qing Peng

J. Compos. Sci. 2023, 7(12), 490; https://doi.org/10.3390/jcs7120490 - 27 Nov 2023

Cited by 2 | Viewed by 1666

Abstract

In this paper, we conducted molecular dynamics simulations to investigate the mechanical properties of double-layer and monolayer irida graphene (IG) structures and the influence of cracks on them. IG, a new two-dimensional material comprising fused rings of 3-6-8 carbon atoms, exhibits exceptional electrical [...] Read more.

In this paper, we conducted molecular dynamics simulations to investigate the mechanical properties of double-layer and monolayer irida graphene (IG) structures and the influence of cracks on them. IG, a new two-dimensional material comprising fused rings of 3-6-8 carbon atoms, exhibits exceptional electrical and thermal conductivity, alongside robust structural stability. We found the fracture stress of the irida graphene structure on graphene sheet exceeds that of the structure comprising solely irida graphene. Additionally, the fracture stress of bilayer graphene significantly surpasses that of bilayer irida graphene. We performed crack analysis in both IG and graphene and observed that perpendicular cracks aligned with the tensile direction result in decreased fracture stress as the crack length increases. Moreover, we found that larger angles in relation to the tensile direction lead to reduced fracture stress. Across all structures, 75° demonstrated the lowest stress and strain. These results offer valuable implications for utilizing bilayer and monolayer IG in the development of advanced nanoscale electronic devices. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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15 pages, 6451 KiB

Open AccessArticle

Atomic Insights into the Structural Properties and Displacement Cascades in Ytterbium Titanate Pyrochlore (Yb₂Ti₂O₇) and High-Entropy Pyrochlores

by M. Mustafa Azeem and Qingyu Wang

J. Compos. Sci. 2023, 7(10), 413; https://doi.org/10.3390/jcs7100413 - 5 Oct 2023

Viewed by 1570

Abstract

Pyrochlore oxides (

A_{2} B_{2} O_{7})

are potential nuclear waste substrate materials due to their superior radiation resistance properties. We performed molecular dynamics simulations to study the structural properties and displacement cascades in ytterbium titanate pyrochlore ( [...] Read more.

Pyrochlore oxides (

A_{2} B_{2} O_{7})

are potential nuclear waste substrate materials due to their superior radiation resistance properties. We performed molecular dynamics simulations to study the structural properties and displacement cascades in ytterbium titanate pyrochlore (

{Yb}_{2} {Ti}_{2} O_{7}

) and high-entropy alloys (HEPy), e.g.,

YbYTiZr O_{7}

,

YbGdTiZr O_{7}

, and

{Yb}_{0.5} Y_{0.5} {Eu}_{0.5} {Gd}_{0.5} TiZr O_{7}

. We computed lattice constants (LC) (

a_{o}

) and threshold displacement energy (E_d). Furthermore, the calculation for

a_{o}

and ionic radius (

r_{i o n i c}

) were performed by substituting a combination of cations at the A and B sites of the original pyrochlore structure. Our simulation results have demonstrated that the lattice constant is proportional to the ionic radius, i.e.,

a_{o} α r_{i o n i c}

. Moreover, the effect of displacement cascades of recoils of energies 1 keV, 2 keV, 5 keV, and 10 keV in different crystallographic directions ([100], [110], [111]) was studied. The number of defects is found to be proportional to the energy of incident primary knock-on atoms (PKA). Additionally, the

E_{d}

of pyrochlore exhibits anisotropy. We also observed that HEPy has a larger

E_{d}

as compared with

{Yb}_{2} {Ti}_{2} O_{7}

. This establishes that

{Yb}_{2} {Ti}_{2} O_{7}

has characteristics of lower radiation damage resistance than HEPy. Our displacement cascade simulation result proposes that HEPy alloys have more tendency for trapping defects. This work will provide atomic insights into developing substrate materials for nuclear waste applications. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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26 pages, 35708 KiB

Open AccessArticle

Numerical Modeling of Single-Lap Shear Bond Tests for Composite-Reinforced Mortar Systems

by Rossana Dimitri, Martina Rinaldi, Marco Trullo and Francesco Tornabene

J. Compos. Sci. 2023, 7(8), 329; https://doi.org/10.3390/jcs7080329 - 14 Aug 2023

Cited by 3 | Viewed by 1397

Abstract

The large demand of reinforcement systems for the rehabilitation of existing concrete and masonry structures, has recently increased the development of innovative methods and advanced systems where the structural mass and weight are reduced, possibly avoiding steel reinforcements, while using non-invasive and reversible [...] Read more.

The large demand of reinforcement systems for the rehabilitation of existing concrete and masonry structures, has recently increased the development of innovative methods and advanced systems where the structural mass and weight are reduced, possibly avoiding steel reinforcements, while using non-invasive and reversible reinforcements made of pre-impregnated fiber nets and mortars in the absence of cement, commonly known as composite-reinforced mortars (CRMs). To date, for such composite materials, few experimental studies have been performed. Their characterization typically follows the guidelines published by the Supreme Council of Public Works. In such a context, the present work aims at studying numerically the fracturing behavior of CRM single-lap shear tests by implementing a cohesive zone model and concrete damage plasticity, in a finite element setting. These specimens are characterized by the presence of a mortar whose mechanical behavior has been defined by means of an analytical approximation based on exponential or polynomial functions. Different fracturing modes are studied numerically within the CRM specimen, involving the matrix and reinforcement phases, as well as the substrate-to-CRM interface. Based on a systematic investigation, the proposed numerical modeling is verified to be a useful tool to predict the response of the entire reinforcement system, in lieu of more costly experimental tests, whose results could be useful for design purposes and could serve as reference numerical solutions for further analytical/experimental investigations on the topic. Full article

(This article belongs to the Special Issue Theoretical and Computational Investigation on Composite Materials)

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