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  • 1
    Online Resource
    Online Resource
    Elsevier BV ; 2020
    In:  Materials Today Communications Vol. 24 ( 2020-09), p. 101070-
    In: Materials Today Communications, Elsevier BV, Vol. 24 ( 2020-09), p. 101070-
    Type of Medium: Online Resource
    ISSN: 2352-4928
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 2829441-5
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  • 2
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Nanomaterials Vol. 13, No. 6 ( 2023-03-18), p. 1095-
    In: Nanomaterials, MDPI AG, Vol. 13, No. 6 ( 2023-03-18), p. 1095-
    Abstract: In the present work, SiO2micro/nanocomposites based on poly-lactic acid (PLA) and an epoxy resin were prepared and experimentally studied. The silica particles were of varying sizes from the nano to micro scale at the same loading. The mechanical and thermomechanical performance, in terms of dynamic mechanical analysis, of the composites prepared was studied in combination with scanning electron microscopy (SEM). Finite element analysis (FEA) has been performed to analyze the Young’s modulus of the composites. A comparison with the results of a well-known analytical model, taking into account the filler’s size and the presence of interphase, was also performed. The general trend is that the reinforcement is higher for the nanosized particles, but it is important to conduct supplementary studies on the combined effect of the matrix type, the size of the nanoparticles, and the dispersion quality. A significant mechanical enhancement was obtained, particularly in the Resin/based nanocomposites.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662255-5
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  • 3
    In: Polymer Composites, Wiley, Vol. 43, No. 4 ( 2022-04), p. 1900-1915
    Abstract: In the present research, a series of hybrid nanocomposites based on polylactic acid (PLA) matrix and mixtures of graphene oxide (GO) with carbon nanotubes (CNTs) or carbon nanofibers (CNFs), at various loadings, were prepared and experimentally studied. Several experimental techniques were employed to analyze the morphology and the thermomechanical performance of the materials, as well as the dielectric properties. The related experimental data support the conclusion that a synergistic effect is exhibited by the PLA/GO/CNT nanocomposites. This effect was verified by the higher mechanical enhancement, the higher crystallinity and the development of conductive paths into the bulk matrix.
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1475935-4
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  • 4
    In: Polymer Testing, Elsevier BV, Vol. 95 ( 2021-03), p. 107102-
    Type of Medium: Online Resource
    ISSN: 0142-9418
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 2015673-X
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2022
    In:  Macromolecular Theory and Simulations Vol. 31, No. 1 ( 2022-01)
    In: Macromolecular Theory and Simulations, Wiley, Vol. 31, No. 1 ( 2022-01)
    Abstract: In the present work, the creep response at specific temperatures and stress level of several polymers has been modeled by a viscoelastic model, analyzed in previous works. In particular, the experimental creep results under thermal cycling of polymers used in bolted flange connections, utilized as components of pressure vessel and piping are employed. The analysis is focused on the experimental results for polymeric flange materials like high density polyethylene and three types of gasket materials, namely poly‐tetrafluoroethylene PTFE (expanded e‐ and virgin v‐) and clickable nucleic acid. It has been proved that by the implementation of the model on a simple creep curve at a specific temperature, the model parameters could be evaluated. Hereafter, by imposing a thermal cycling process, two more parameters, associated with thermal ratcheting, could be acquired. It is found that the thermal ratcheting behavior exhibited by the employed materials, could be captured with a good accuracy. Given that the effect of thermal ratcheting on the long‐time performance of polymers in targeted applications is a crucial issue, the research findings in the present work are encouraging for the design of appropriate materials, and the prediction of thermal ratcheting.
    Type of Medium: Online Resource
    ISSN: 1022-1344 , 1521-3919
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1475028-4
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  • 6
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2023
    In:  Mechanics of Time-Dependent Materials
    In: Mechanics of Time-Dependent Materials, Springer Science and Business Media LLC
    Abstract: In the present work, a thorough description of the creep response of polymers in both linear and nonlinear viscoelastic domains is presented. According to the proposed model, the polymeric structure is considered as an ensemble of meso-regions linked with each other while they can cooperatively relax and change their positions. Each meso-region has its own energy barrier that needs to be overcome for a transition to occur. It was found that the distribution function, followed by the energy barriers, attains a decisive role, given that it is associated with the distribution of retardation times and with their particular effect on the materials’ time evolution. The crucial role of the imposed stress in a creep experiment by its influence on the retardation time spectrum of the polymeric structure was extensively analyzed. The proposed model has been successfully validated by a series of creep data in a variety of temperatures and stress levels for polymeric materials, studied experimentally elsewhere. Furthermore, the model’s capability to predict the long-term creep response was analytically shown.
    Type of Medium: Online Resource
    ISSN: 1385-2000 , 1573-2738
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2003935-9
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  • 7
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  Polymer Composites Vol. 44, No. 9 ( 2023-09), p. 5619-5632
    In: Polymer Composites, Wiley, Vol. 44, No. 9 ( 2023-09), p. 5619-5632
    Abstract: In this work, an extensive study on the glass transition temperature ( T g ), dynamic fragility and activation energy ( E a ) for a variety polymeric nanocomposite materials, based on four different types of polymeric matrices reinforced with carbonaceous nanofillers, and SiO 2 has been performed. Referring to the dynamic mechanical analysis data obtained in the author's previous works, the dynamic fragility and activation energy were calculated and examined. Depending on the polymeric type, different behavior was detected, as far as the fragility dependence on nanofiller type and loading is concerned, whereas the T g variation was also investigated. A general trend of a decreasing dynamic fragility with increasing T g was found, with the exception of Polylactic acid (PLA)/hybrid nanocomposites. A relation between nanofillers synergy and dynamic fragility variation has been achieved, namely the more homogenous nanofillers dispersion (and the synergistic effect between nanofillers), was associated with higher dynamic fragility values. Furthermore, the inter‐particle distance increment may lead to an increased fragility and the Resin/SiO2 nanocomposites appear to follow this rule. In addition, strain sweep experiments were conducted to analyze the connection between fragility and damping of the polymer nanocomposites. The PLA/hybrid carbonaceous nanocomposites reveal an essential damping enhancement, associated with fragility lowering.
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1475935-4
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  • 8
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Polymer Engineering & Science Vol. 61, No. 6 ( 2021-06), p. 1732-1741
    In: Polymer Engineering & Science, Wiley, Vol. 61, No. 6 ( 2021-06), p. 1732-1741
    Abstract: In the present work, a comparative study on the capability of two approaches to successfully interconvert linear viscoelastic functions is performed. The main concept arises from our previous works, where a polymeric material is treated as a collection of meso‐regions, each one of them with a specific energy barrier. The linking between meso‐regions and their rearrangements leads to a time‐dependent constitutive equation. A crucial issue is the distribution of the energy barriers of the meso‐regions, revealing the importance of the distributed nature of the polymeric structure. In this work, the effect of the distribution type was examined by assuming either a Gaussian distribution function or a normalized loss modulus distribution, which can be evaluated from the loss modulus experimental data. Four different polymers were examined and it was proved that both treatments can satisfactorily predict the creep and relaxation function, once the model parameters are evaluated on the basis of dynamic moduli experimental data.
    Type of Medium: Online Resource
    ISSN: 0032-3888 , 1548-2634
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2006718-5
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Journal of Applied Polymer Science Vol. 138, No. 41 ( 2021-11-05)
    In: Journal of Applied Polymer Science, Wiley, Vol. 138, No. 41 ( 2021-11-05)
    Abstract: In the present work, the creep response of nanocomposites based on metallocene linear low density polyethylene (mLLDPE), reinforced with three types of carbonaceous nanofillers, namely carbon nanotubes (CNTs), graphene oxide (GO) platelets, and carbon nanofibers (CNFs) was experimentally studied. The effect of the nanofiller loading and the hybrid character of nanocomposites on the creep resistance of the nanocompsites was analyzed. In all cases, the creep resistance of the nanocomposites examined has been postulated. To support these results, creep has been modeled by a power creep law, while the creep‐ recovery modeling was achieved by a viscoelastic model. The implementation of the viscoelastic model has been made by assuming that the nanocomposite's structure can be represented by a physical network, with the dispersed nanofillers participating in the molecular rearrangements, which take place upon the imposition of stress. The time dependent constitutive equation involves a relaxation function, based on a Gaussian type distribution function, associated with the energy barriers that molecular segments need to overcome, for transitions to occur. It was found that creep‐recovery strain could be accurately captured with the same set of parameters, whereas the number of required model parameters was quite lower than that in the widely known viscoelastic models.
    Type of Medium: Online Resource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491105-X
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