Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis
Flexible pipe end fittings (EFs) transfer axial loads by embedding tensile armor within epoxy matrices. The integrity of bonding between the armor and resin profoundly influences the EF load-bearing capacity. This study investigated the debonding failure mechanism at the epoxy-resin–tensile-armor in...
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MDPI AG
2025-03-01
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| Series: | Journal of Marine Science and Engineering |
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| author | Tao Zhang Qingzhen Lu Shengjie Xu Yuanchao Yin Jun Yan Qianjin Yue |
| author_facet | Tao Zhang Qingzhen Lu Shengjie Xu Yuanchao Yin Jun Yan Qianjin Yue |
| author_sort | Tao Zhang |
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| description | Flexible pipe end fittings (EFs) transfer axial loads by embedding tensile armor within epoxy matrices. The integrity of bonding between the armor and resin profoundly influences the EF load-bearing capacity. This study investigated the debonding failure mechanism at the epoxy-resin–tensile-armor interface in flexible pipe end fittings through integrated experimental and numerical approaches. Combining tensile tests with digital image correlation (DIC) and cohesive zone modeling (CZM), the research quantified the impacts of interfacial defects and adhesive properties on structural integrity. Specimens with varying bond lengths (40–60 mm) and defect diameters (0–4 mm) revealed that defects significantly reduced load-bearing capacity, with larger defects exacerbating strain localization and accelerating failure. A dimensionless parameter, the defect-size-to-bond-length ratio (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>λ</mi><mo>=</mo><mi>D</mi><mo>/</mo><mn>2</mn><mi>L</mi></mrow></semantics></math></inline-formula>), was proposed to unify defect impact analysis, demonstrating its nonlinear relationship with failure load reduction. High-toughness adhesives, such as Sikaforce<sup>®</sup> 7752, mitigated defect sensitivity by redistributing stress concentrations, outperforming brittle alternatives like Araldite<sup>®</sup> AV138. DIC captured real-time strain evolution and crack propagation, validating strain concentrations up to 3.2 at defect edges, while CZM simulations achieved high accuracy (errors: 3.0–7.2%) in predicting failure loads. Critical thresholds for λ (λ < 0.025 for negligible impact; λ > 0.05 requiring defect control or high-toughness adhesives) were established, providing actionable guidelines for manufacturing optimization and adhesive selection. By bridging experimental dynamics with predictive modeling, this work advances the design of robust deepwater energy infrastructure through defect management and material innovation, offering practical strategies to enhance structural reliability in critical applications. |
| format | Article |
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| institution | OA Journals |
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| language | English |
| publishDate | 2025-03-01 |
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| series | Journal of Marine Science and Engineering |
| spelling | doaj-art-359c73ff5f2c437c8acb9a10d86588172025-08-20T02:28:31ZengMDPI AGJournal of Marine Science and Engineering2077-13122025-03-0113467710.3390/jmse13040677Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect AnalysisTao Zhang0Qingzhen Lu1Shengjie Xu2Yuanchao Yin3Jun Yan4Qianjin Yue5State Key Laboratory of Structural Analysis for Industrial Equipment, School of Mechanics and Aerospace Engineering, Dalian University of Technology, Dalian 116024, ChinaSchool of Chemical Engineering, Ocean and Life Sciences, Dalian University of Technology, Panjin 124221, ChinaSchool of Chemical Engineering, Ocean and Life Sciences, Dalian University of Technology, Panjin 124221, ChinaSchool of Chemical Engineering, Ocean and Life Sciences, Dalian University of Technology, Panjin 124221, ChinaState Key Laboratory of Structural Analysis for Industrial Equipment, School of Mechanics and Aerospace Engineering, Dalian University of Technology, Dalian 116024, ChinaState Key Laboratory of Structural Analysis for Industrial Equipment, School of Mechanics and Aerospace Engineering, Dalian University of Technology, Dalian 116024, ChinaFlexible pipe end fittings (EFs) transfer axial loads by embedding tensile armor within epoxy matrices. The integrity of bonding between the armor and resin profoundly influences the EF load-bearing capacity. This study investigated the debonding failure mechanism at the epoxy-resin–tensile-armor interface in flexible pipe end fittings through integrated experimental and numerical approaches. Combining tensile tests with digital image correlation (DIC) and cohesive zone modeling (CZM), the research quantified the impacts of interfacial defects and adhesive properties on structural integrity. Specimens with varying bond lengths (40–60 mm) and defect diameters (0–4 mm) revealed that defects significantly reduced load-bearing capacity, with larger defects exacerbating strain localization and accelerating failure. A dimensionless parameter, the defect-size-to-bond-length ratio (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>λ</mi><mo>=</mo><mi>D</mi><mo>/</mo><mn>2</mn><mi>L</mi></mrow></semantics></math></inline-formula>), was proposed to unify defect impact analysis, demonstrating its nonlinear relationship with failure load reduction. High-toughness adhesives, such as Sikaforce<sup>®</sup> 7752, mitigated defect sensitivity by redistributing stress concentrations, outperforming brittle alternatives like Araldite<sup>®</sup> AV138. DIC captured real-time strain evolution and crack propagation, validating strain concentrations up to 3.2 at defect edges, while CZM simulations achieved high accuracy (errors: 3.0–7.2%) in predicting failure loads. Critical thresholds for λ (λ < 0.025 for negligible impact; λ > 0.05 requiring defect control or high-toughness adhesives) were established, providing actionable guidelines for manufacturing optimization and adhesive selection. By bridging experimental dynamics with predictive modeling, this work advances the design of robust deepwater energy infrastructure through defect management and material innovation, offering practical strategies to enhance structural reliability in critical applications.https://www.mdpi.com/2077-1312/13/4/677flexible pipe end fittingdebonding failuredefect toleranceadhesive toughnessdigital image correlation (DIC) |
| spellingShingle | Tao Zhang Qingzhen Lu Shengjie Xu Yuanchao Yin Jun Yan Qianjin Yue Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis Journal of Marine Science and Engineering flexible pipe end fitting debonding failure defect tolerance adhesive toughness digital image correlation (DIC) |
| title | Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis |
| title_full | Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis |
| title_fullStr | Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis |
| title_full_unstemmed | Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis |
| title_short | Interfacial Failure in Flexible Pipe End Fittings: DIC and Cohesive Zone Modeling for Defect Analysis |
| title_sort | interfacial failure in flexible pipe end fittings dic and cohesive zone modeling for defect analysis |
| topic | flexible pipe end fitting debonding failure defect tolerance adhesive toughness digital image correlation (DIC) |
| url | https://www.mdpi.com/2077-1312/13/4/677 |
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