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Special Issue "Structural Mechanics of Composite Materials and Structures"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editors

Dr. Francesco Tornabene
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Guest Editor
Prof. Dr. Rossana Dimitri
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Guest Editor
Department of Innovation Engineering, University of Salento, Lecce, Italy
Interests: fracture mechanics; debonding; contact mechanics; isogeometric analysis; mechanics of solids; structural models for shells; plates and beams; numerical analysis; innovative composite materials; dynamics
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Special Issue Information

Dear Colleagues,

The mechanical modeling of composite materials and structures at different scales is a subject of great interest among the scientific community due to their large application in many fields of engineering and science, e.g., aerospace components, aircrafts, boat hulls and sails, car bodies, long span roofs, as well as biomedical prostheses, electronic devices, and drones. For such complex materials and structures, the application of advanced theoretical formulations and computational methodologies at different scales represents a key aspect gathering together experts and young researchers to follow the increased requirements of accuracy.

Composite materials are well known to improve the mechanical properties of strength and stiffness, together with the increased thermal properties and lower levels of weight. These properties can affect the mechanical behavior of beams, plates, and shells, in terms of statics, dynamics, and buckling response, as well as their nonlinear fracturing phenomena occurring at different scales. Enhanced structures and composite materials feature internal length scales and a nonlocal behavior, whose response could be analyzed through parametric investigations, 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 typical examples of SMART applications could be in 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 to control and monitor the vibrational behavior or the static deflection of several composites.

Classical and high-performance advanced theories, multiscale approaches, and regularization and approximation of crack discontinuities can be presented and discussed to this end. Contributions on theoretical and numerical aspects are welcome from scientists working on mathematics and mechanics to improve the current state of the art on the topic.

Prof. Francesco Tornabene
Prof. 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 papers will be 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. Molecules 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 2000 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

  • Auxetic materials
  • Buckling behavior
  • Carbon nanotubes
  • Composite structures
  • Constitutive models
  • Damage
  • Dynamics
  • Fracture mechanics
  • Functionally graded materials
  • Metamaterials
  • Smart materials
  • Statics

Published Papers (8 papers)

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Research

Open AccessArticle
Synthesis of a Series of Dual-Functional Chelated Titanate Bonding Agents and Their Application Performances in Composite Solid Propellants
Molecules 2020, 25(22), 5353; https://doi.org/10.3390/molecules25225353 - 16 Nov 2020
Viewed by 354
Abstract
Titanate-based bonding agents are a class of efficient bonding agents for improving the mechanical properties of composite solid propellants, a kind of special composite material. However, high solid contents often deteriorate the rheological properties of propellant slurry, which limits the application of bonding [...] Read more.
Titanate-based bonding agents are a class of efficient bonding agents for improving the mechanical properties of composite solid propellants, a kind of special composite material. However, high solid contents often deteriorate the rheological properties of propellant slurry, which limits the application of bonding agents. To solve this problem, a series of long-chain alkyl chelated titanate binders, N-n-octyl-N, N-dihydroxyethyl-lactic acid-titanate (DLT-8), N-n-dodecyl-N, N-dihydroxyethyl-lactic acid-titanate (DLT-12), N-n-hexadecyl-N, N-Dihydroxyethyl-lactic acid-titanate (DLT-16), were designed and synthesized in the present work. The infrared absorption spectral changes of solid propellants caused by binder coating and adhesion degrees of the bonding agents on the oxidant surface were determined by micro-infrared microscopy (MIR) and X-ray photoelectron spectroscopy (XPS), respectively, to characterize the interaction properties of the bonding agents with oxidants, ammonium perchlorate (AP) and hexogen (RDX), in solid propellants. The further application tests suggest that the bonding agents can effectively interact with the oxidants and effectively improve the mechanical and rheological properties of the four-component hydroxyl-terminated polybutadiene (HTPB) composite solid propellants containing AP and RDX. The agent with longer bond chain length can improve the rheological properties of the propellant slurry more significantly, and the propellant of the best mechanical properties was obtained with DLT-12, consistent with the conclusion obtained in the interfacial interaction study. Our work has provided a new method for simultaneously improving the processing performance and rheological properties of propellants and offered an important guidance for the bonding agent design. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessFeature PaperArticle
Ionotropic Gelation of Chitosan for Next-Generation Composite Proton Conducting Flat Structures
Molecules 2020, 25(7), 1632; https://doi.org/10.3390/molecules25071632 - 02 Apr 2020
Cited by 2 | Viewed by 1314
Abstract
(1) Background: Ionotropic gelation of cost-effective and eco-friendly biopolymer chitosan (Chit) is a novel and promising approach to the one-step synthesis of proton-conducting fuel cell bio-membranes.The method discovered by the author in 2011 and subsequently drowned among very few papers. This work aimed [...] Read more.
(1) Background: Ionotropic gelation of cost-effective and eco-friendly biopolymer chitosan (Chit) is a novel and promising approach to the one-step synthesis of proton-conducting fuel cell bio-membranes.The method discovered by the author in 2011 and subsequently drowned among very few papers. This work aimed to relaunch this method through clear and effective communication of new unpublished results emphasizing the key aspects of this topic for successful dissemination of the results and significant future developments. (2) Methods and results: The mechanism of in-situ ionotropic gelation of Chit on an alumina substrate by phosphotungtate anions (PWA3−) was discussed and analyzed. The study sheds light on the effect of prolonged post-treatment in phosphotungstic acid (PWA) solution on the obtained chitosan/phosphotungstate (Chit-PWA) flat structures. Methods used included combined structural (XRD), thermal-gravimetric (DTG), electrochemical (in-situ EIS), compositional (EDX),morphological analysis (SEM), as well as the performances in a low temperature H2/O2 fuel cell(4) Conclusions: This contribution discloses novel possibilities aimed at increasing the impact of ionotropic gelation of chitosan on the scientific community working on the synthesis of novel proton conductive bio-composite membranes and structures. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessArticle
A Modified Couple Stress Elasticity for Non-Uniform Composite Laminated Beams Based on the Ritz Formulation
Molecules 2020, 25(6), 1404; https://doi.org/10.3390/molecules25061404 - 19 Mar 2020
Cited by 3 | Viewed by 749
Abstract
Due to the large application of tapered beams in smart devices, such as scanning tunneling microscopes (STM), nano/micro electromechanical systems (NEMS/MEMS), atomic force microscopes (AFM), as well as in military aircraft applications, this study deals with the vibration behavior of laminated composite non-uniform [...] Read more.
Due to the large application of tapered beams in smart devices, such as scanning tunneling microscopes (STM), nano/micro electromechanical systems (NEMS/MEMS), atomic force microscopes (AFM), as well as in military aircraft applications, this study deals with the vibration behavior of laminated composite non-uniform nanobeams subjected to different boundary conditions. The micro-structural size-dependent free vibration response of composite laminated Euler–Bernoulli beams is here analyzed based on a modified couple stress elasticity, which accounts for the presence of a length scale parameter. The governing equations and boundary conditions of the problem are developed using the Hamilton’s principle, and solved by means of the Rayleigh–Ritz method. The accuracy and stability of the proposed formulation is checked through a convergence and comparative study with respect to the available literature. A large parametric study is conducted to investigate the effect of the length-scale parameter, non-uniformity parameter, size dimension and boundary conditions on the natural frequencies of laminated composite tapered beams, as useful for design and optimization purposes of small-scale devices, due to their structural tailoring capabilities, damage tolerance, and their potential for creating reduction in weight. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessArticle
Effects of Cyclic Freeze–Thaw on the Steel Bar Reinforced New-To-Old Concrete Interface
Molecules 2020, 25(5), 1251; https://doi.org/10.3390/molecules25051251 - 10 Mar 2020
Cited by 1 | Viewed by 762
Abstract
Frost damage of concrete has significant effects on the safety and durability of concrete structures in cold regions, and the concrete structures after repair and reinforcement are still threatened by cyclic freezing and thawing. In this study, the new-to-old concrete interface was reinforced [...] Read more.
Frost damage of concrete has significant effects on the safety and durability of concrete structures in cold regions, and the concrete structures after repair and reinforcement are still threatened by cyclic freezing and thawing. In this study, the new-to-old concrete interface was reinforced by steel bar. The shear strength of the new-to-old concrete interface was tested after the new-to-old combination was subjected to cyclic freeze–thaw. The effects of the diameter of the steel bar, the compressive strength of new concrete, the number of freeze–thaw cycles and the freezing temperatures on the shear properties of new-to-old concrete interface were studied. The results showed that, in a certain range, the shear strength of the interface was proportional to the diameter of the steel bar and the strength of the new concrete. Meanwhile, the shear strength of the reinforced interface decreased with the decreasing of the freezing temperature and the increasing of the number of freeze–thaw cycles. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessArticle
Effect of Polyvinyl Alcohol on the Rheological Properties of Cement Mortar
Molecules 2020, 25(3), 754; https://doi.org/10.3390/molecules25030754 - 10 Feb 2020
Cited by 2 | Viewed by 658
Abstract
Polyvinyl alcohol (PVA) is a kind of water-soluble polymer, which has been widely used in different industries due to its excellent mechanical and chemical properties. In this paper, the effects of polyvinyl alcohol with different hydrolysis and polymerization degrees on the rheological properties [...] Read more.
Polyvinyl alcohol (PVA) is a kind of water-soluble polymer, which has been widely used in different industries due to its excellent mechanical and chemical properties. In this paper, the effects of polyvinyl alcohol with different hydrolysis and polymerization degrees on the rheological properties of cement mortar are studied. The results show that the rheological properties of PVA-modified cement mortar can be described by the modified Bingham model. The yield stress of modified cement mortar is less than that of unmodified mortar when the degree of polymerization and the content of PVA are small. With the increase of polyvinyl alcohol content and polymerization degree, the yield stress and plastic viscosity of modified cement mortar increase sharply, which are larger than those of the unmodified cement mortar. However, the effect of hydrolysis degree of PVA on yield stress and plastic viscosity of modified cement mortar is not obvious. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessArticle
Rheological, Thermal, Superficial, and Morphological Properties of Thermoplastic Achira Starch Modified with Lactic Acid and Oleic Acid
Molecules 2019, 24(24), 4433; https://doi.org/10.3390/molecules24244433 - 04 Dec 2019
Cited by 3 | Viewed by 1230
Abstract
The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and [...] Read more.
The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessFeature PaperArticle
Nonlocal Buckling Analysis of Composite Curved Beams Reinforced with Functionally Graded Carbon Nanotubes
Molecules 2019, 24(15), 2750; https://doi.org/10.3390/molecules24152750 - 29 Jul 2019
Cited by 13 | Viewed by 1036
Abstract
This work deals with the size-dependent buckling response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) (FG-CNTRC) curved beams based on a higher-order shear deformation beam theory in conjunction with the Eringen Nonlocal Differential Model (ENDM). The material properties were estimated using the rule [...] Read more.
This work deals with the size-dependent buckling response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) (FG-CNTRC) curved beams based on a higher-order shear deformation beam theory in conjunction with the Eringen Nonlocal Differential Model (ENDM). The material properties were estimated using the rule of mixtures. The Hamiltonian principle was employed to derive the governing equations of the problem which were, in turn, solved via the Galerkin method to obtain the critical buckling load of FG-CNTRC curved beams with different boundary conditions. A detailed parametric study was carried out to investigate the influence of the nonlocal parameter, CNTs volume fraction, opening angle, slenderness ratio, and boundary conditions on the mechanical buckling characteristics of FG-CNTRC curved beams. A large parametric investigation was performed on the mechanical buckling behavior of FG-CNTRC curved beams, which included different CNT distribution schemes, as useful for design purposes in many practical engineering applications. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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Open AccessArticle
Preparation of a Novel Lignin Nanosphere Adsorbent for Enhancing Adsorption of Lead
Molecules 2019, 24(15), 2704; https://doi.org/10.3390/molecules24152704 - 25 Jul 2019
Cited by 6 | Viewed by 792
Abstract
Carboxymethyl lignin nanospheres (CLNPs) were synthesized by a two-step method using microwave irradiation and antisolvent. The morphology and structure of CLNPs were characterized by 31P-NMR, FTIR, and SEM, and the results showed that they had an average diameter of 73.9 nm, a [...] Read more.
Carboxymethyl lignin nanospheres (CLNPs) were synthesized by a two-step method using microwave irradiation and antisolvent. The morphology and structure of CLNPs were characterized by 31P-NMR, FTIR, and SEM, and the results showed that they had an average diameter of 73.9 nm, a surface area of 8.63 m2 or 3.2 times larger than the original lignin, and abundant carboxyl functional groups of 1.8 mmol/g. The influence of dosage, pH, contact time, and concentration on the adsorption of metal ions onto CLNPs were analyzed, and the maximum adsorption capacity of CLNPs for Pb(II) was found to be 333.26 mg/g, which is significantly higher than other lignin-based adsorbents and conventional adsorbents. Adsorption kinetics and isotherms indicated that the adsorption of lead ions in water onto CLNPs followed the pseudo-second-order model based on monolayer chemisorption mechanism. The main chemical interaction between CLNPs and lead ions was chelation. CLNPs also showed an excellent recycling performance, with only 27.0% adsorption capacity loss after 10 consecutive adsorption–desorption cycles. Full article
(This article belongs to the Special Issue Structural Mechanics of Composite Materials and Structures)
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