PSI - Issue 66

36 Carl H. Wolf et al. / Procedia Structural Integrity 66 (2024) 26–37 Carl H. Wolf, Sebastian Henkel, Christian Düreth, Maik Gude and Horst Biermann / Structural Integrity Procedia 00 (2025) 000–000 11 4. Summary and conclusions The fatigue crack growth behavior of carbon fiber fabric-reinforced plastic composites was investigated. Specimens with a hole-notch geometry were analyzed. The energy release rate under uniaxial loading was determined using finite element analysis. In addition, a virtual measurement clip was used to evaluate both uniaxial and biaxial loading conditions. The measurement results were then compared with existing literature data. The virtual measuring clip offers several advantages, such as low measurement effort, symmetry-related cancellation of individual loading components, and the possibility of application at medium loads without the need for a force zero point. Thanks to the variable gauge length of the virtual measuring clip, it can be adapted to different materials and test setups. However, the accuracy of the results depends on the exact determination of the position of the crack tip. In addition, deviations in the measurement result can occur if only one crack edge moves. In terms of fatigue crack growth, the virtual measurement clip allowed the determination of the crack tip loading. It also enabled the calculations of Mode I, Mode II, and equivalent energy release rates. A higher compressive load reduced the Mode I loading, resulting in lower energy release rates, slower fatigue crack growth rates, and lower equivalent energy release rates. Higher fabric weights also resulted in lower crack growth rates. While finite element calculations were performed for uniaxial loading with symmetrical cracks, discrepancies were found between these results and those from the virtual clip, likely due to the assumption of a linear-elastic material model. Further, FE calculations with the measured crack propagation are currently carried out. Acknowledgments The authors would like to thank the German Research Foundation for funding the project “Description of the fatigue behavior of fabric-reinforced fiber-plastic composites under combined interlaminar shear and out-of-plane compression loading” (project number 450147819). Furthermore, the authors would like to thank Dr. Eric Breitbarth and his team for their support in the use of CrackPy. References Christian Düreth, Daniel Weck, Robert Böhm, Mike Thieme, Maik Gude, Sebastian Henkel, Carl Wolf, and Horst Biermann. Determining the Damage and Failure Behaviour of Textile Reinforced Composites under Combined In-Plane and Out-of-Plane Loading. Materials , 13(21):4772, oct 2020. [3] H. A. Richard, M. Fulland, and M. Sander. Theoretical crack path prediction. Fatigue & Fracture of Engineering Materials & Structures , 28(1-2):3–12, 2005. [4] H. A. Richard and M. Sander. Ermüdungsrisse – Erkennen, sicher beurteilen, vermeiden , pages 51–105. Springer Fachmedien Wiesbaden, 2012. [5] F. Sacchetti, W. J. B. Grouve, L. L. Warnet, and I. F. Villegas. Effect of resin-rich bond line thickness and fibre migration on the toughness of unidirectional Carbon/PEEK joints. Composites Part A: Applied Science and Manufacturing , 109:197–206, June 2018. [6] K.-H. Schwalbe and D. Hellmann. Correlation of stable crack growth with J-integral and crack tip opening displacement, effects of geometry, size, and material. Technical report, 1984. [7] T. Strohmann, D. Melching, P. Florian, A. Klein, D. Eric, G. Requena, and E. Breitbarth. Crack Analysis Tool in Python - CrackPy, 2022. [8] S. A. Sutton. Fatigue crack propagation in an epoxy polymer. Engineering Fracture Mechanics , 6(3):587–595, oct 1974. [9] C. H. Wolf. Einfluss phasenverschobener Beanspruchungen auf das Risswachstumsverhalten von planar-biaxial beanspruchten, kreuzförmigen Proben aus einem austenitischen Stahl . PhD thesis, TU Bergakademie Freiberg, 2022. [1] C. Düreth, D. Weck, R. Böhm, M. Thieme, M. Gude, C. H. Wolf, S. Henkel, and H. Biermann. Interlaminar shear strength enhancement under out-of-plane compression of fabric reinforcements - A review on meso and macro scale. In Proceedings of the 18th European Conference on Composite Materials , pages 10–18, Athen, Greece, 2018. [2]