Frequency–Direction Coupling in the Glass Transition Response of Thermally Aged Wet-Layup Unidirectional Carbon/Epoxy Composites.
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| Title: | Frequency–Direction Coupling in the Glass Transition Response of Thermally Aged Wet-Layup Unidirectional Carbon/Epoxy Composites. |
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| Authors: | Kokku, Kruthika1 (AUTHOR), Acharya, Rabina1,2 (AUTHOR), Karbhari, Vistasp M.1,2 (AUTHOR) vkarbhari@uta.edu |
| Source: | Polymers (20734360). Mar2026, Vol. 18 Issue 6, p680. 26p. |
| Subjects: | Dynamic mechanical analysis, Frequency response, Polymer degradation, Deterioration of materials, Glass transitions, Carbon composites, Anisotropy, Polymeric composites |
| Abstract: | Dynamic mechanical thermal analysis (DMTA) is widely used to assess the effects of process- and environment-induced changes in polymer matrix composites, with the glass transition temperature (Tg) often reported from the tan d peak at a single excitation frequency. However, such an approach neglects the inherently kinetic nature of the glass transition and may obscure thermally induced changes in relaxation response. Multi-frequency DMTA was employed to investigate the evolution of glass transition response of a wet-layup unidirectional carbon/epoxy composite subjected to thermal aging at temperatures ranging from 66 °C to 260 °C for periods up to 72 h, using unexposed (23 °C) results as an ambient baseline reference. Tests were conducted using a single cantilever mode in both longitudinal and transverse configurations over a range of excitation frequencies from 0.3 to 30 Hz. Results demonstrate that thermal exposure affects not only the absolute value of the glass transition temperature, but also its frequency sensitivity and directional dependence. A frequency sensitivity parameter and a directional amplification factor are introduced to quantify frequency–direction coupling. While post-cure-dominated aging regimes exhibit relatively stable coupling behavior, degradation-dominated conditions at elevated temperatures and longer periods of thermal exposure lead to pronounced increases in transverse frequency sensitivity, which reflects early evolution of matrix- and interphase-level deterioration. These findings highlight the value of multi-frequency DMTA with tests in both primary directions for the mechanistic assessment of effects of thermo-oxidative response in polymer matrix composites. [ABSTRACT FROM AUTHOR] |
| Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
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| Header | DbId: egs DbLabel: Engineering Source An: 192641981 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Frequency–Direction Coupling in the Glass Transition Response of Thermally Aged Wet-Layup Unidirectional Carbon/Epoxy Composites. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Kokku%2C+Kruthika%22">Kokku, Kruthika</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Acharya%2C+Rabina%22">Acharya, Rabina</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Karbhari%2C+Vistasp+M%2E%22">Karbhari, Vistasp M.</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<i> vkarbhari@uta.edu</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Polymers+%2820734360%29%22">Polymers (20734360)</searchLink>. Mar2026, Vol. 18 Issue 6, p680. 26p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Dynamic+mechanical+analysis%22">Dynamic mechanical analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Frequency+response%22">Frequency response</searchLink><br /><searchLink fieldCode="DE" term="%22Polymer+degradation%22">Polymer degradation</searchLink><br /><searchLink fieldCode="DE" term="%22Deterioration+of+materials%22">Deterioration of materials</searchLink><br /><searchLink fieldCode="DE" term="%22Glass+transitions%22">Glass transitions</searchLink><br /><searchLink fieldCode="DE" term="%22Carbon+composites%22">Carbon composites</searchLink><br /><searchLink fieldCode="DE" term="%22Anisotropy%22">Anisotropy</searchLink><br /><searchLink fieldCode="DE" term="%22Polymeric+composites%22">Polymeric composites</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Dynamic mechanical thermal analysis (DMTA) is widely used to assess the effects of process- and environment-induced changes in polymer matrix composites, with the glass transition temperature (Tg) often reported from the tan d peak at a single excitation frequency. However, such an approach neglects the inherently kinetic nature of the glass transition and may obscure thermally induced changes in relaxation response. Multi-frequency DMTA was employed to investigate the evolution of glass transition response of a wet-layup unidirectional carbon/epoxy composite subjected to thermal aging at temperatures ranging from 66 °C to 260 °C for periods up to 72 h, using unexposed (23 °C) results as an ambient baseline reference. Tests were conducted using a single cantilever mode in both longitudinal and transverse configurations over a range of excitation frequencies from 0.3 to 30 Hz. Results demonstrate that thermal exposure affects not only the absolute value of the glass transition temperature, but also its frequency sensitivity and directional dependence. A frequency sensitivity parameter and a directional amplification factor are introduced to quantify frequency–direction coupling. While post-cure-dominated aging regimes exhibit relatively stable coupling behavior, degradation-dominated conditions at elevated temperatures and longer periods of thermal exposure lead to pronounced increases in transverse frequency sensitivity, which reflects early evolution of matrix- and interphase-level deterioration. These findings highlight the value of multi-frequency DMTA with tests in both primary directions for the mechanistic assessment of effects of thermo-oxidative response in polymer matrix composites. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.3390/polym18060680 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 26 StartPage: 680 Subjects: – SubjectFull: Dynamic mechanical analysis Type: general – SubjectFull: Frequency response Type: general – SubjectFull: Polymer degradation Type: general – SubjectFull: Deterioration of materials Type: general – SubjectFull: Glass transitions Type: general – SubjectFull: Carbon composites Type: general – SubjectFull: Anisotropy Type: general – SubjectFull: Polymeric composites Type: general Titles: – TitleFull: Frequency–Direction Coupling in the Glass Transition Response of Thermally Aged Wet-Layup Unidirectional Carbon/Epoxy Composites. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Kokku, Kruthika – PersonEntity: Name: NameFull: Acharya, Rabina – PersonEntity: Name: NameFull: Karbhari, Vistasp M. IsPartOfRelationships: – BibEntity: Dates: – D: 15 M: 03 Text: Mar2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 20734360 Numbering: – Type: volume Value: 18 – Type: issue Value: 6 Titles: – TitleFull: Polymers (20734360) Type: main |
| ResultId | 1 |
