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Recent Advances in Theoretical and Computational Modeling of Composite Materials...
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Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (10 October 2021) | Viewed by 40382

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Francesco Tornabene

grade E-Mail Website
Guest Editor
Department of Innovation Engineering, University of Salento, 73100 Lecce, Italy
Interests: theory of shells, plates, arches, and beams; generalized differential quadrature; FEM; SFEM; WFEM; IGA; SFIGA; WFIGA; advanced composite materials; functionally graded materials; nanomaterials and nanotechnology
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Rossana Dimitri

E-Mail Website
Guest Editor
Department of Innovation Engineering, University of Salento, 73100 Lecce, Italy
Interests: damage and fracture mechanics; contact mechanics; structural mechanics; solid mechanics; computational mechanics; advanced composite materials; nanomaterials and nanotechnology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In a context where the mechanical modeling of composite materials at different scales requires an increased accuracy in many engineering problems and applications, e.g., aerospace components, aircrafts, boat hulls and sails, car bodies, long span roofs, as well as electronic devices, and drones, this Special Issue aims at gathering together experts and young researchers in theoretical and computational modeling of heterogeneous materials and complex structures.

Composite materials and structures feature internal length scales and nonlocal behaviors, whose response could be analyzed systematically, while including the effect of the staking sequences, ply orientations, agglomeration of nanoparticles, volume fractions of the constituents, and porosity level.

Studies on fiber-reinforced composites and laminates, functionally graded materials (FGMs), Carbon nanotubes (CNTs), graphene nanoplatelets, SMART constituents, as well as innovative and advanced classes of composites are welcome. Some examples could be represented by large stroke SMART actuators, piezoelectric sensors, shape memory alloys, magnetostrictive and electrostrictive materials, as well as auxetic components and angle-tow laminates. These constituents could be included in the lamination schemes of SMART structures for a successful control and monitoring of their vibrational behavior and/or static deflection.

Classical and high-performance advanced theories and multiscale approaches are welcome, together with the development of enhanced nonlocal damage and fracturing models, able to capture the formation and propagation of the internal cracks related to the heterogeneity of complex materials and interfaces.

Prof. Dr. Francesco Tornabene
Prof. Dr. Rossana Dimitri
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Adhesion 
  • Advanced computational methods 
  • Auxetic materials 
  • Buckling behavior 
  • Carbon nanotubes 
  • Complex materials 
  • Composite beams, plates, and shells
  • Constitutive models
  • Damage 
  • Delamination 
  • Dynamics
  • Fracture mechanics 
  • Functionally graded materials
  • Homogenization techniques
  • Metamaterials 
  • Nanostructures
  • Smart materials

Published Papers (14 papers)

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Editorial

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4 pages, 195 KiB  
Editorial
Special Issue on Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures
by Francesco Tornabene and Rossana Dimitri
Appl. Sci. 2022, 12(9), 4715; https://0-doi-org.brum.beds.ac.uk/10.3390/app12094715 - 07 May 2022
Viewed by 1006
Abstract
The advancement in manufacturing technology and scientific research have improved the development of enhanced composite materials with tailored properties depending on their design requirements in many engineering fields, as well as in thermal and energy management [...] Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)

Research

Jump to: Editorial

38 pages, 1308 KiB  
Article
3D Stress Analysis of Multilayered Functionally Graded Plates and Shells under Moisture Conditions
by Salvatore Brischetto and Roberto Torre
Appl. Sci. 2022, 12(1), 512; https://0-doi-org.brum.beds.ac.uk/10.3390/app12010512 - 05 Jan 2022
Cited by 8 | Viewed by 1554
Abstract
This paper presents the steady-state stress analysis of single-layered and multilayered plates and shells embedding Functionally Graded Material (FGM) layers under moisture conditions. This solution relies on an exact layer-wise approach; the formulation is unique despite the geometry. It studies spherical and cylindrical [...] Read more.
This paper presents the steady-state stress analysis of single-layered and multilayered plates and shells embedding Functionally Graded Material (FGM) layers under moisture conditions. This solution relies on an exact layer-wise approach; the formulation is unique despite the geometry. It studies spherical and cylindrical shells, cylinders, and plates in an orthogonal mixed curvilinear coordinate system (α, β, z). The moisture conditions are defined at the external surfaces and evaluated in the thickness direction under steady-state conditions following three procedures. This solution handles the 3D Fick diffusion equation, the 1D Fick diffusion equation, and the a priori assumed linear profile. The paper discusses their assumptions and the different results they deliver. Once defined, the moisture content acts as an external load; this leads to a system of three non-homogeneous second-order differential equilibrium equations. The 3D problem is reduced to a system of partial differential equations in the thickness coordinate, solved via the exponential matrix method. It returns the displacements and their z-derivatives as a direct result. The paper validates the model by comparing the results with 3D analytical models proposed in the literature and numerical models. Then, new results are presented for one-layered and multilayered FGM plates, cylinders, and cylindrical and spherical shells, considering different moisture contents, thickness ratios, and material laws. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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21 pages, 5749 KiB  
Article
Three-Dimensional Buckling Analysis of Functionally Graded Saturated Porous Rectangular Plates under Combined Loading Conditions
by Faraz Kiarasi, Masoud Babaei, Kamran Asemi, Rossana Dimitri and Francesco Tornabene
Appl. Sci. 2021, 11(21), 10434; https://0-doi-org.brum.beds.ac.uk/10.3390/app112110434 - 06 Nov 2021
Cited by 26 | Viewed by 2056
Abstract
The present work studies the buckling behavior of functionally graded (FG) porous rectangular plates subjected to different loading conditions. Three different porosity distributions are assumed throughout the thickness, namely, a nonlinear symmetric, a nonlinear asymmetric and a uniform distribution. A novel approach is [...] Read more.
The present work studies the buckling behavior of functionally graded (FG) porous rectangular plates subjected to different loading conditions. Three different porosity distributions are assumed throughout the thickness, namely, a nonlinear symmetric, a nonlinear asymmetric and a uniform distribution. A novel approach is proposed here based on a combination of the generalized differential quadrature (GDQ) method and finite elements (FEs), labeled here as the FE-GDQ method, while assuming a Biot’s constitutive law in lieu of the classical elasticity relations. A parametric study is performed systematically to study the sensitivity of the buckling response of porous structures, to different input parameters, such as the aspect ratio, porosity and Skempton coefficients, along with different boundary conditions (BCs) and porosity distributions, with promising and useful conclusions for design purposes of many engineering structural porous members. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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25 pages, 23449 KiB  
Article
Theoretical and Numerical Solution for the Bending and Frequency Response of Graphene Reinforced Nanocomposite Rectangular Plates
by Mehran Safarpour, Ali Forooghi, Rossana Dimitri and Francesco Tornabene
Appl. Sci. 2021, 11(14), 6331; https://0-doi-org.brum.beds.ac.uk/10.3390/app11146331 - 08 Jul 2021
Cited by 22 | Viewed by 2025
Abstract
In this work, we study the vibration and bending response of functionally graded graphene platelets reinforced composite (FG-GPLRC) rectangular plates embedded on different substrates and thermal conditions. The governing equations of the problem along with boundary conditions are determined by employing the minimum [...] Read more.
In this work, we study the vibration and bending response of functionally graded graphene platelets reinforced composite (FG-GPLRC) rectangular plates embedded on different substrates and thermal conditions. The governing equations of the problem along with boundary conditions are determined by employing the minimum total potential energy and Hamilton’s principle, within a higher-order shear deformation theoretical setting. The problem is solved both theoretically and numerically by means of a Navier-type exact solution and a generalized differential quadrature (GDQ) method, respectively, whose results are successfully validated against the finite element predictions performed in the commercial COMSOL code, and similar outcomes available in the literature. A large parametric study is developed to check for the sensitivity of the response to different foundation properties, graphene platelets (GPL) distribution patterns, volume fractions of the reinforcing phase, as well as the surrounding environment and boundary conditions, with very interesting insights from a scientific and design standpoint. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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20 pages, 4786 KiB  
Article
Buckling Analysis of CNTRC Curved Sandwich Nanobeams in Thermal Environment
by Ahmed Amine Daikh, Mohammed Sid Ahmed Houari, Behrouz Karami, Mohamed A. Eltaher, Rossana Dimitri and Francesco Tornabene
Appl. Sci. 2021, 11(7), 3250; https://0-doi-org.brum.beds.ac.uk/10.3390/app11073250 - 05 Apr 2021
Cited by 38 | Viewed by 3181
Abstract
This paper presents a mathematical continuum model to investigate the static stability buckling of cross-ply single-walled (SW) carbon nanotube reinforced composite (CNTRC) curved sandwich nanobeams in thermal environment, based on a novel quasi-3D higher-order shear deformation theory. The study considers possible nano-scale size [...] Read more.
This paper presents a mathematical continuum model to investigate the static stability buckling of cross-ply single-walled (SW) carbon nanotube reinforced composite (CNTRC) curved sandwich nanobeams in thermal environment, based on a novel quasi-3D higher-order shear deformation theory. The study considers possible nano-scale size effects in agreement with a nonlocal strain gradient theory, including a higher-order nonlocal parameter (material scale) and gradient length scale (size scale), to account for size-dependent properties. Several types of reinforcement material distributions are assumed, namely a uniform distribution (UD) as well as X- and O- functionally graded (FG) distributions. The material properties are also assumed to be temperature-dependent in agreement with the Touloukian principle. The problem is solved in closed form by applying the Galerkin method, where a numerical study is performed systematically to validate the proposed model, and check for the effects of several factors on the buckling response of CNTRC curved sandwich nanobeams, including the reinforcement material distributions, boundary conditions, length scale and nonlocal parameters, together with some geometry properties, such as the opening angle and slenderness ratio. The proposed model is verified to be an effective theoretical tool to treat the thermal buckling response of curved CNTRC sandwich nanobeams, ranging from macroscale to nanoscale, whose examples could be of great interest for the design of many nanostructural components in different engineering applications. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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21 pages, 14927 KiB  
Article
Theoretical Analysis of Fractional Viscoelastic Flow in Circular Pipes: General Solutions
by Dmitry Gritsenko and Roberto Paoli
Appl. Sci. 2020, 10(24), 9093; https://0-doi-org.brum.beds.ac.uk/10.3390/app10249093 - 18 Dec 2020
Cited by 7 | Viewed by 2382
Abstract
Fractional calculus is a relatively old yet emerging field of mathematics with the widest range of engineering and biomedical applications. Despite being an incredibly powerful tool, it, however, requires promotion in the engineering community. Rheology is undoubtedly one of the fields where fractional [...] Read more.
Fractional calculus is a relatively old yet emerging field of mathematics with the widest range of engineering and biomedical applications. Despite being an incredibly powerful tool, it, however, requires promotion in the engineering community. Rheology is undoubtedly one of the fields where fractional calculus has become an integral part of cutting-edge research. There exists extensive literature on the theoretical, experimental, and numerical treatment of various fractional viscoelastic flows in constraint geometries. However, the general theoretical approach that unites several most commonly used models is missing. Here we present exact analytical solutions for fractional viscoelastic flow in a circular pipe. We find velocity profiles and shear stresses for fractional Maxwell, Kelvin–Voigt, Zener, Poynting–Thomson, and Burgers models. The dynamics of these quantities are studied with respect to normalized pipe radius, fractional orders, and elastic moduli ratio. Three different types of behavior are identified: monotonic increase, resonant, and aperiodic oscillations. The models developed are applicable in the widest material range and allow for the alteration of the balance between viscous and elastic properties of the materials. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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13 pages, 464 KiB  
Article
Theoretical Analysis of Fractional Viscoelastic Flow in Circular Pipes: Parametric Study
by Dmitry Gritsenko and Roberto Paoli
Appl. Sci. 2020, 10(24), 9080; https://0-doi-org.brum.beds.ac.uk/10.3390/app10249080 - 18 Dec 2020
Cited by 3 | Viewed by 1555
Abstract
Pipe flow is one of the most commonly used models to describe fluid dynamics. The concept of fractional derivative has been recently found very useful and much more accurate in predicting dynamics of viscoelastic fluids compared with classic models. In this paper, we [...] Read more.
Pipe flow is one of the most commonly used models to describe fluid dynamics. The concept of fractional derivative has been recently found very useful and much more accurate in predicting dynamics of viscoelastic fluids compared with classic models. In this paper, we capitalize on our previous study and consider space-time dynamics of flow velocity and stress for fractional Maxwell, Zener, and Burgers models. We demonstrate that the behavior of these quantities becomes much more complex (compared to integer-order classical models) when adjusting fractional order and elastic parameters. We investigate mutual influence of fractional orders and consider their limiting value combinations. Finally, we show that the models developed can be reduced to classical ones when appropriate fractional orders are set. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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22 pages, 5127 KiB  
Article
Nonlinear Vibration of Functionally Graded Graphene Nanoplatelets Polymer Nanocomposite Sandwich Beams
by Mohammad Sadegh Nematollahi, Hossein Mohammadi, Rossana Dimitri and Francesco Tornabene
Appl. Sci. 2020, 10(16), 5669; https://0-doi-org.brum.beds.ac.uk/10.3390/app10165669 - 15 Aug 2020
Cited by 31 | Viewed by 2512
Abstract
We provide an analytical investigation of the nonlinear vibration behavior of thick sandwich nanocomposite beams reinforced by functionally graded (FG) graphene nanoplatelet (GPL) sheets, with a power-law-based distribution throughout the thickness. We assume the total amount of the reinforcement phase to remain constant [...] Read more.
We provide an analytical investigation of the nonlinear vibration behavior of thick sandwich nanocomposite beams reinforced by functionally graded (FG) graphene nanoplatelet (GPL) sheets, with a power-law-based distribution throughout the thickness. We assume the total amount of the reinforcement phase to remain constant in the beam, while defining a relationship between the GPL maximum weight fraction, the power-law parameter, and the thickness of the face sheets. The shear and rotation effects are here considered using a higher-order laminated beam model. The nonlinear partial differential equations (PDEs) of motion are derived from the Von Kármán strain-displacement relationships, here solved by applying an expansion of free vibration modes. The numerical results demonstrate the key role of the amplitudes on the vibration response of GPL-reinforced sandwich beams, whose nonlinear oscillation behavior is very important in the physical science, mechanical structures and other mathematical analyses. The sensitivity of the response to the total amount of GPLs is explored herein, along with the possible effects related to the power-law parameter, the structural geometry, and the environmental conditions. The results indicate that changing the nanofiller distribution patterns with the proposed model can remarkably increase or decrease the effective stiffness of laminated composite beams. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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20 pages, 4945 KiB  
Article
Vibration Analysis of Piezoelectric Cantilever Beams with Bimodular Functionally-Graded Properties
by Hong-Xia Jing, Xiao-Ting He, Da-Wei Du, Dan-Dan Peng and Jun-Yi Sun
Appl. Sci. 2020, 10(16), 5557; https://0-doi-org.brum.beds.ac.uk/10.3390/app10165557 - 11 Aug 2020
Cited by 11 | Viewed by 2162
Abstract
Piezoelectric materials have been found to have many electromechanical applications in intelligent devices, generally in the form of the flexible cantilever element; thus, the analysis to the corresponding cantilever is of importance, especially when advanced mechanical properties of piezoelectric materials should be taken [...] Read more.
Piezoelectric materials have been found to have many electromechanical applications in intelligent devices, generally in the form of the flexible cantilever element; thus, the analysis to the corresponding cantilever is of importance, especially when advanced mechanical properties of piezoelectric materials should be taken into account. In this study, the vibration problem of a piezoelectric cantilever beam with bimodular functionally-graded properties is solved via analytical and numerical methods. First, based on the equivalent modulus of elasticity, the analytical solution for vibration of the cantilever beam is easily derived. By the simplified mechanical model based on subarea in tension and compression, as well as on the layer-wise theory, the bimodular functionally-graded materials are numerically simulated; thus, the numerical solution of the problem studied is obtained. The comparison between the theoretical solution and numerical study is carried out, showing that the result is reliable. This study shows that the bimodular functionally-graded properties may change, to some extent, the dynamic response of the piezoelectric cantilever beam; however, the influence could be relatively small and unobvious. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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16 pages, 7385 KiB  
Article
Damage Investigation of Carbon-Fiber-Reinforced Plastic Laminates with Fasteners Subjected to Lightning Current Components C and D
by Jian Chen, Xiaolei Bi, Juan Liu and Zhengcai Fu
Appl. Sci. 2020, 10(6), 2147; https://0-doi-org.brum.beds.ac.uk/10.3390/app10062147 - 21 Mar 2020
Cited by 11 | Viewed by 2796
Abstract
The damage induced by lightning strikes in carbon-fiber-reinforced plastic (CFRP) laminates with fasteners is a complex multiphysics coupling process. To clarify the effects of different lightning current components on the induced damage, components C and D were used in simulated lightning strike tests. [...] Read more.
The damage induced by lightning strikes in carbon-fiber-reinforced plastic (CFRP) laminates with fasteners is a complex multiphysics coupling process. To clarify the effects of different lightning current components on the induced damage, components C and D were used in simulated lightning strike tests. Ultrasonic C-scans and stereomicroscopy were used to evaluate the damage in the tested specimens. In addition, the electrothermal coupling theory was adopted to model the different effects of the arc and the current flowing through the laminate (hereinafter referred to as the conduction current) on CFRP laminates with fasteners under different lightning current components. Component C, which has a low current amplitude and a long duration, ablated and gasified the fastener and caused less damage to the CFRP laminate. Under component C, the heat produced by the arc played a leading role in damage generation. Component D, which has a high current amplitude and a short duration, caused serious surface and internal damage in the CFRP laminate and little damage to the fastener. Under component D, the damage was mainly caused by the Joule heat generated by the conduction current. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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19 pages, 8045 KiB  
Article
Dynamics Modeling and Theoretical Study of the Two-Axis Four-Gimbal Coarse–Fine Composite UAV Electro-Optical Pod
by Cheng Shen, Shixun Fan, Xianliang Jiang, Ruoyu Tan and Dapeng Fan
Appl. Sci. 2020, 10(6), 1923; https://0-doi-org.brum.beds.ac.uk/10.3390/app10061923 - 11 Mar 2020
Cited by 9 | Viewed by 9790
Abstract
In the UAV electro-optical pod of the two-axis four-gimbal, the characteristics of a coarse–fine composite structure and the complexity of dynamics modeling affect the entire system’s high precision control performance. The core goal of this paper is to solve the high precision control [...] Read more.
In the UAV electro-optical pod of the two-axis four-gimbal, the characteristics of a coarse–fine composite structure and the complexity of dynamics modeling affect the entire system’s high precision control performance. The core goal of this paper is to solve the high precision control of a two-axis four-gimbal electro-optical pod through dynamic modeling and theoretical study. In response to this problem, we used finite element analysis (FEA) and stress study of the key component to design the structure. The gimbals adopt the aerospace material 7075-t3510 aluminum alloy in order to meet the requirements of an ultralight weight of less than 1 kg. According to the Euler rigid body dynamics model, the transmission path and kinematics coupling compensation matrix between the two-axis four-gimbal structures are obtained. The coarse–fine composite self-correction drive equation in the Cartesian system is derived to solve the pre-selection and check problem of the mechatronic under high-precision control. Finally, the modeling method is substituted into the disturbance observer (DOB) disturbance suppression experiment, which can monitor and compensate for the motion coupling between gimbal structures in real time. Results show that the disturbance suppression impact of the DOB method with dynamics model is increased by up to 90% compared to PID (Proportion Integration Differentiation method) and is 25% better than the traditional DOB method. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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30 pages, 4226 KiB  
Article
Dynamic Stability of Bi-Directional Functionally Graded Porous Cylindrical Shells Embedded in an Elastic Foundation
by Farshid Allahkarami, Hasan Tohidi, Rossana Dimitri and Francesco Tornabene
Appl. Sci. 2020, 10(4), 1345; https://0-doi-org.brum.beds.ac.uk/10.3390/app10041345 - 16 Feb 2020
Cited by 32 | Viewed by 2529
Abstract
This paper investigates the dynamic buckling of bi-directional (BD) functionally graded (FG) porous cylindrical shells for various boundary conditions, where the FG material is modeled by means of power law functions with even and uneven porosity distributions of ceramic and metal phases. The [...] Read more.
This paper investigates the dynamic buckling of bi-directional (BD) functionally graded (FG) porous cylindrical shells for various boundary conditions, where the FG material is modeled by means of power law functions with even and uneven porosity distributions of ceramic and metal phases. The third-order shear deformation theory (TSDT) is adopted to derive the governing equations of the problem via the Hamilton’s principle. The generalized differential quadrature (GDQ) method is applied together with the Bolotin scheme as numerical strategy to solve the problem, and to draw the dynamic instability region (DIR) of the structure. A large parametric study examines the effect of different boundary conditions at the extremities of the cylindrical shell, as well as the sensitivity of the dynamic stability to different thickness-to-radius ratios, length-to-radius ratios, transverse and longitudinal power indexes, porosity volume fractions, and elastic foundation constants. Based on results, the dynamic stability of BD-FG cylindrical shells can be controlled efficiently by selecting appropriate power indexes along the desired directions. Furthermore, the DIR is highly sensitive to the porosity distribution and to the extent of transverse and longitudinal power indexes. The numerical results could be of great interest for many practical applications, as civil, mechanical or aerospace engineering, as well as for energy devices or biomedical systems. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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12 pages, 3246 KiB  
Article
First-Principles Forecast of Gapless Half-Metallic and Spin-Gapless Semiconducting Materials: Case Study of Inverse Ti2CoSi-Based Compounds
by Liang Zhang, Shengjie Dong, Jiangtao Du, Yi-Lin Lu, Hui Zhao and Liefeng Feng
Appl. Sci. 2020, 10(3), 782; https://0-doi-org.brum.beds.ac.uk/10.3390/app10030782 - 22 Jan 2020
Cited by 4 | Viewed by 2492
Abstract
First-principles calculations were used to investigate several inverse Ti2CoSi-based compounds. Our results indicate that Ti2CoSi could transform from a spin-gapless semiconductor to a half metal if a quarter of the Co atoms are replaced by Ti. Ti2.25Co [...] Read more.
First-principles calculations were used to investigate several inverse Ti2CoSi-based compounds. Our results indicate that Ti2CoSi could transform from a spin-gapless semiconductor to a half metal if a quarter of the Co atoms are replaced by Ti. Ti2.25Co0.75Si would keep stable half-metallic properties in a large range of lattice parameter under the effect of hydrostatic strain, and would become a gapless half metal under the effect of tetragonal distortion. Furthermore, we substituted B, Al, Ga, P, As, and Sb for Si in the Ti2.25Co0.75Si compound. Our results demonstrate that Ti2.25Co0.75Si0.5B0.5, Ti2.25Co0.75Si0.5Al0.5, and Ti2.25Co0.75Si0.5Ga0.5 are half-metallic ferromagnetic materials, and Ti2.25Co0.75Si0.5P0.5, Ti2.25Co0.75Si0.5As0.5, and Ti2.25Co0.75Si0.5Sb0.5 are spin-gapless semiconducting materials. The introduced impurity atoms may adjust the valence electron configuration, change the charge concentration, and shift the location of the Fermi level. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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18 pages, 2561 KiB  
Article
Theoretical Study and Application of the Reinforcement of Prestressed Concrete Cylinder Pipes with External Prestressed Steel Strands
by Lijun Zhao, Tiesheng Dou, Bingqing Cheng, Shifa Xia, Jinxin Yang, Qi Zhang, Meng Li and Xiulin Li
Appl. Sci. 2019, 9(24), 5532; https://0-doi-org.brum.beds.ac.uk/10.3390/app9245532 - 16 Dec 2019
Cited by 9 | Viewed by 2912
Abstract
Prestressed concrete cylinder pipes (PCCPs) can suffer from prestress loss caused by wire-breakage, leading to a reduction in load-carrying capacity or a rupture accident. Reinforcement of PCCPs with external prestressed steel strands is an effective way to enhance a deteriorating pipe’s ability to [...] Read more.
Prestressed concrete cylinder pipes (PCCPs) can suffer from prestress loss caused by wire-breakage, leading to a reduction in load-carrying capacity or a rupture accident. Reinforcement of PCCPs with external prestressed steel strands is an effective way to enhance a deteriorating pipe’s ability to withstand the design load. One of the principal advantages of this reinforcement is that there is no need to drain the pipeline. A theoretical derivation is performed, and this tentative design method could be used to determine the area of prestressed steel strands and the corresponding center spacing in terms of prestress loss. The prestress losses of strands are refined and the normal stress between the strands and the pipe wall are assumed to be distributed as a trigonometric function instead of uniformly. This derivation configures the prestress of steel strands to meet the requirements of ultimate limit states, serviceability limit states, and quasi-permanent limit states, considering the tensile strength of the concrete core and the mortar coating, respectively. This theory was applied to the reinforcement design of a PCCP with broken wires (with a diameter of 2000 mm), and a prototype test is carried out to verify the effect of the reinforcement. The load-carrying capacity of the deteriorating PCCPs after reinforcement reached that of the original design level. The research presented in this paper could provide technical recommendations for the application of the reinforcement of PCCPs with external prestressed steel strands. Full article
(This article belongs to the Special Issue Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures)
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