---
_id: '54281'
abstract:
- lang: eng
  text: <jats:title>Abstract</jats:title><jats:p>Polycarbonate (PC) is an amorphous
    polymer that is an extremely robust material with a high tenacity, and thus suitable
    for a lightweight construction with glass‐like transparency. Due to these advantageous
    properties, PC is often used in industry for example in medical devices, automotive
    headlamps, sporting equipment, electronics, and a variety of other products. PC
    is often subjected to uniaxial and biaxial loading conditions. Therefore, reliable
    material models have to take into account the various resulting experimental effects.
    For those reasons, we investigate PC specimens under uniaxial and biaxial loading
    by using different stretch rates and loading scenarios. In addition to that, we
    propose methods for optical measurement of local stretches to obtain the approximated
    local true stress. In future work, the displacement fields and the resulting reaction
    forces will be used for parameter identification of constitutive equations.</jats:p>
author:
- first_name: Ayoub
  full_name: Hamdoun, Ayoub
  id: '57708'
  last_name: Hamdoun
- first_name: Rolf
  full_name: Mahnken, Rolf
  id: '335'
  last_name: Mahnken
citation:
  ama: Hamdoun A, Mahnken R. Experimental investigations of uniaxial and biaxial cold
    stretching within PC‐films and bars using optical measurements. <i>PAMM</i>. Published
    online 2024. doi:<a href="https://doi.org/10.1002/pamm.202300114">10.1002/pamm.202300114</a>
  apa: Hamdoun, A., &#38; Mahnken, R. (2024). Experimental investigations of uniaxial
    and biaxial cold stretching within PC‐films and bars using optical measurements.
    <i>PAMM</i>. <a href="https://doi.org/10.1002/pamm.202300114">https://doi.org/10.1002/pamm.202300114</a>
  bibtex: '@article{Hamdoun_Mahnken_2024, title={Experimental investigations of uniaxial
    and biaxial cold stretching within PC‐films and bars using optical measurements},
    DOI={<a href="https://doi.org/10.1002/pamm.202300114">10.1002/pamm.202300114</a>},
    journal={PAMM}, publisher={Wiley}, author={Hamdoun, Ayoub and Mahnken, Rolf},
    year={2024} }'
  chicago: Hamdoun, Ayoub, and Rolf Mahnken. “Experimental Investigations of Uniaxial
    and Biaxial Cold Stretching within PC‐films and Bars Using Optical Measurements.”
    <i>PAMM</i>, 2024. <a href="https://doi.org/10.1002/pamm.202300114">https://doi.org/10.1002/pamm.202300114</a>.
  ieee: 'A. Hamdoun and R. Mahnken, “Experimental investigations of uniaxial and biaxial
    cold stretching within PC‐films and bars using optical measurements,” <i>PAMM</i>,
    2024, doi: <a href="https://doi.org/10.1002/pamm.202300114">10.1002/pamm.202300114</a>.'
  mla: Hamdoun, Ayoub, and Rolf Mahnken. “Experimental Investigations of Uniaxial
    and Biaxial Cold Stretching within PC‐films and Bars Using Optical Measurements.”
    <i>PAMM</i>, Wiley, 2024, doi:<a href="https://doi.org/10.1002/pamm.202300114">10.1002/pamm.202300114</a>.
  short: A. Hamdoun, R. Mahnken, PAMM (2024).
date_created: 2024-05-14T09:06:26Z
date_updated: 2024-09-26T11:25:10Z
department:
- _id: '9'
- _id: '154'
doi: 10.1002/pamm.202300114
language:
- iso: eng
publication: PAMM
publication_identifier:
  issn:
  - 1617-7061
  - 1617-7061
publication_status: published
publisher: Wiley
status: public
title: Experimental investigations of uniaxial and biaxial cold stretching within
  PC‐films and bars using optical measurements
type: journal_article
user_id: '57708'
year: '2024'
...
---
_id: '54279'
article_number: '126981'
author:
- first_name: Ayoub
  full_name: Hamdoun, Ayoub
  id: '57708'
  last_name: Hamdoun
- first_name: Rolf
  full_name: Mahnken, Rolf
  id: '335'
  last_name: Mahnken
citation:
  ama: Hamdoun A, Mahnken R. Uniaxial and biaxial experimental investigation of glassy
    polymers. <i>Polymer</i>. 2024;299. doi:<a href="https://doi.org/10.1016/j.polymer.2024.126981">10.1016/j.polymer.2024.126981</a>
  apa: Hamdoun, A., &#38; Mahnken, R. (2024). Uniaxial and biaxial experimental investigation
    of glassy polymers. <i>Polymer</i>, <i>299</i>, Article 126981. <a href="https://doi.org/10.1016/j.polymer.2024.126981">https://doi.org/10.1016/j.polymer.2024.126981</a>
  bibtex: '@article{Hamdoun_Mahnken_2024, title={Uniaxial and biaxial experimental
    investigation of glassy polymers}, volume={299}, DOI={<a href="https://doi.org/10.1016/j.polymer.2024.126981">10.1016/j.polymer.2024.126981</a>},
    number={126981}, journal={Polymer}, publisher={Elsevier BV}, author={Hamdoun,
    Ayoub and Mahnken, Rolf}, year={2024} }'
  chicago: Hamdoun, Ayoub, and Rolf Mahnken. “Uniaxial and Biaxial Experimental Investigation
    of Glassy Polymers.” <i>Polymer</i> 299 (2024). <a href="https://doi.org/10.1016/j.polymer.2024.126981">https://doi.org/10.1016/j.polymer.2024.126981</a>.
  ieee: 'A. Hamdoun and R. Mahnken, “Uniaxial and biaxial experimental investigation
    of glassy polymers,” <i>Polymer</i>, vol. 299, Art. no. 126981, 2024, doi: <a
    href="https://doi.org/10.1016/j.polymer.2024.126981">10.1016/j.polymer.2024.126981</a>.'
  mla: Hamdoun, Ayoub, and Rolf Mahnken. “Uniaxial and Biaxial Experimental Investigation
    of Glassy Polymers.” <i>Polymer</i>, vol. 299, 126981, Elsevier BV, 2024, doi:<a
    href="https://doi.org/10.1016/j.polymer.2024.126981">10.1016/j.polymer.2024.126981</a>.
  short: A. Hamdoun, R. Mahnken, Polymer 299 (2024).
date_created: 2024-05-14T09:05:05Z
date_updated: 2024-09-26T11:25:29Z
department:
- _id: '9'
- _id: '154'
- _id: '321'
doi: 10.1016/j.polymer.2024.126981
intvolume: '       299'
language:
- iso: eng
publication: Polymer
publication_identifier:
  issn:
  - 0032-3861
publication_status: published
publisher: Elsevier BV
quality_controlled: '1'
status: public
title: Uniaxial and biaxial experimental investigation of glassy polymers
type: journal_article
user_id: '57708'
volume: 299
year: '2024'
...
---
_id: '54280'
abstract:
- lang: eng
  text: <jats:title>Abstract</jats:title><jats:p>Cold forming of polycarbonate films
    results in the formation of shear bands in the necking zone. The numerical results
    obtained from standard viscoplastic material models exhibit mesh size dependency,
    requiring mathematical regularization. For this purpose, we present in this work
    a large deformation gradient theory for a viscoplastic isotropic material model
    published before. We extend our model to a micromorphic model by introducing a
    new micromorphic variable as an additional degree of freedom along with its first
    gradient. This variable represents a microequivalent plastic strain. The relation
    between the macroequivalent plastic strain and the micromorphic variable is accomplished
    by a micromorphic coupling modulus. This coupling forces proximity between the
    macro- and microvariables, leading to the targeted regularization effect. The
    micromorphic model is implemented as a three-dimensional initial boundary value
    problem in an in-house finite element tool. The analysis is performed for both
    uniaxial and biaxial specimens. The provided numerical examples show the ability
    of our model to regularize shear bands within the specimens and address the issue
    of localization.</jats:p>
author:
- first_name: Ayoub
  full_name: Hamdoun, Ayoub
  id: '57708'
  last_name: Hamdoun
- first_name: Rolf
  full_name: Mahnken, Rolf
  id: '335'
  last_name: Mahnken
citation:
  ama: Hamdoun A, Mahnken R. A large deformation gradient theory for glassy polymers
    by means of micromorphic regularization. <i>Archive of Applied Mechanics</i>.
    2024;94(5):1221-1242. doi:<a href="https://doi.org/10.1007/s00419-024-02570-0">10.1007/s00419-024-02570-0</a>
  apa: Hamdoun, A., &#38; Mahnken, R. (2024). A large deformation gradient theory
    for glassy polymers by means of micromorphic regularization. <i>Archive of Applied
    Mechanics</i>, <i>94</i>(5), 1221–1242. <a href="https://doi.org/10.1007/s00419-024-02570-0">https://doi.org/10.1007/s00419-024-02570-0</a>
  bibtex: '@article{Hamdoun_Mahnken_2024, title={A large deformation gradient theory
    for glassy polymers by means of micromorphic regularization}, volume={94}, DOI={<a
    href="https://doi.org/10.1007/s00419-024-02570-0">10.1007/s00419-024-02570-0</a>},
    number={5}, journal={Archive of Applied Mechanics}, publisher={Springer Science
    and Business Media LLC}, author={Hamdoun, Ayoub and Mahnken, Rolf}, year={2024},
    pages={1221–1242} }'
  chicago: 'Hamdoun, Ayoub, and Rolf Mahnken. “A Large Deformation Gradient Theory
    for Glassy Polymers by Means of Micromorphic Regularization.” <i>Archive of Applied
    Mechanics</i> 94, no. 5 (2024): 1221–42. <a href="https://doi.org/10.1007/s00419-024-02570-0">https://doi.org/10.1007/s00419-024-02570-0</a>.'
  ieee: 'A. Hamdoun and R. Mahnken, “A large deformation gradient theory for glassy
    polymers by means of micromorphic regularization,” <i>Archive of Applied Mechanics</i>,
    vol. 94, no. 5, pp. 1221–1242, 2024, doi: <a href="https://doi.org/10.1007/s00419-024-02570-0">10.1007/s00419-024-02570-0</a>.'
  mla: Hamdoun, Ayoub, and Rolf Mahnken. “A Large Deformation Gradient Theory for
    Glassy Polymers by Means of Micromorphic Regularization.” <i>Archive of Applied
    Mechanics</i>, vol. 94, no. 5, Springer Science and Business Media LLC, 2024,
    pp. 1221–42, doi:<a href="https://doi.org/10.1007/s00419-024-02570-0">10.1007/s00419-024-02570-0</a>.
  short: A. Hamdoun, R. Mahnken, Archive of Applied Mechanics 94 (2024) 1221–1242.
date_created: 2024-05-14T09:05:40Z
date_updated: 2024-09-26T11:25:44Z
department:
- _id: '9'
- _id: '154'
- _id: '321'
doi: 10.1007/s00419-024-02570-0
intvolume: '        94'
issue: '5'
language:
- iso: eng
page: 1221-1242
publication: Archive of Applied Mechanics
publication_identifier:
  issn:
  - 0939-1533
  - 1432-0681
publication_status: published
publisher: Springer Science and Business Media LLC
quality_controlled: '1'
status: public
title: A large deformation gradient theory for glassy polymers by means of micromorphic
  regularization
type: journal_article
user_id: '57708'
volume: 94
year: '2024'
...
---
_id: '54282'
abstract:
- lang: eng
  text: <jats:title>Abstract</jats:title><jats:p>Stretching of polycarbonate films
    leads to the formation of shear bands in the necking zone [1]. Standard viscoplastic
    material models render mesh size dependent results, which requires a mathematical
    regularization. To this end, we present a finite strain gradient theory for a
    viscoplastic, isotropic material model where we extend the model presented in
    [2] to a micromorphic model by introducing a new micromorphic variable as an additional
    degree of freedom with its first gradient [3, 4]. The variable here has the meaning
    of a micro plastic strain, and is coupled with the macro plastic by a micro penalty
    term, forcing the macro‐plastic strain to be close to the micro‐plastic strain
    for the targeted shear band regularization effect. We have implemented the model
    equations as a three dimensional initial boundary value problem in an in house
    FE‐tool, to simulate different geometries with different thickness and to compare
    it the experimental tests. The analysis is performed for a uniaxial tensile geometry
    as well as for a biaxial tensile geometry. The numerical examples show the ability
    of the model to regularize the shear bands and solve the problem of localization.</jats:p>
author:
- first_name: Ayoub
  full_name: Hamdoun, Ayoub
  id: '57708'
  last_name: Hamdoun
- first_name: Rolf
  full_name: Mahnken, Rolf
  id: '335'
  last_name: Mahnken
citation:
  ama: Hamdoun A, Mahnken R. A finite strain gradient theory for viscoplasticity by
    means of micromorphic regularization. <i>PAMM</i>. 2023;22(1). doi:<a href="https://doi.org/10.1002/pamm.202200074">10.1002/pamm.202200074</a>
  apa: Hamdoun, A., &#38; Mahnken, R. (2023). A finite strain gradient theory for
    viscoplasticity by means of micromorphic regularization. <i>PAMM</i>, <i>22</i>(1).
    <a href="https://doi.org/10.1002/pamm.202200074">https://doi.org/10.1002/pamm.202200074</a>
  bibtex: '@article{Hamdoun_Mahnken_2023, title={A finite strain gradient theory for
    viscoplasticity by means of micromorphic regularization}, volume={22}, DOI={<a
    href="https://doi.org/10.1002/pamm.202200074">10.1002/pamm.202200074</a>}, number={1},
    journal={PAMM}, publisher={Wiley}, author={Hamdoun, Ayoub and Mahnken, Rolf},
    year={2023} }'
  chicago: Hamdoun, Ayoub, and Rolf Mahnken. “A Finite Strain Gradient Theory for
    Viscoplasticity by Means of Micromorphic Regularization.” <i>PAMM</i> 22, no.
    1 (2023). <a href="https://doi.org/10.1002/pamm.202200074">https://doi.org/10.1002/pamm.202200074</a>.
  ieee: 'A. Hamdoun and R. Mahnken, “A finite strain gradient theory for viscoplasticity
    by means of micromorphic regularization,” <i>PAMM</i>, vol. 22, no. 1, 2023, doi:
    <a href="https://doi.org/10.1002/pamm.202200074">10.1002/pamm.202200074</a>.'
  mla: Hamdoun, Ayoub, and Rolf Mahnken. “A Finite Strain Gradient Theory for Viscoplasticity
    by Means of Micromorphic Regularization.” <i>PAMM</i>, vol. 22, no. 1, Wiley,
    2023, doi:<a href="https://doi.org/10.1002/pamm.202200074">10.1002/pamm.202200074</a>.
  short: A. Hamdoun, R. Mahnken, PAMM 22 (2023).
date_created: 2024-05-14T09:06:38Z
date_updated: 2024-05-14T09:15:38Z
doi: 10.1002/pamm.202200074
intvolume: '        22'
issue: '1'
language:
- iso: eng
publication: PAMM
publication_identifier:
  issn:
  - 1617-7061
  - 1617-7061
publication_status: published
publisher: Wiley
status: public
title: A finite strain gradient theory for viscoplasticity by means of micromorphic
  regularization
type: journal_article
user_id: '57708'
volume: 22
year: '2023'
...