PSI - Issue 54

Johannes Kaiser et al. / Procedia Structural Integrity 54 (2024) 26–33 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

32

7

Especially for the low-molecular PC, a significant increase of the temperature at the crack tip can be observed. It can also be seen that the temperature increase of the PS is significantly lower, which is due to the lower intermolecular forces of the polymer chains. Stable crack growth has always occurred at the temperatures determined here. Tests with instable crack growth have again led to a further increase in temperature. However, these findings must be verified with an increased recording rate of the thermographic camera. 5. Conclusion and outlook The combination of a digital image correlation system and a thermography camera was used to obtain a high time and location resolution of the temperature rise at the crack tip during the failure process. In the analyzed velocity range the thermography results showed temperature peaks for polycarbonate with up to 90 °C and for polystyrene nearly 45 °C. Those differences are due to different structure of the polymers and the attraction between the polymer chains. Furthermore it is now possible to link every temperature data with the deformation data and determine the J-Integral values. In a next step the test set up should be transferred to a high speed tensile testing device which allows testing speed up to 20 m/s. For the shown results a clear dependency of the temperature data and failure mechanism of the velocity was seen and then could be analyzed further. In addition, further work is planned to optimize the test, such as improving the maximum magnifications of the thermographic camera by using an optical bench, optimizing the geometry of the test specimen for applying acoustic sensors, determining the relationship between acoustic and thermal waves during the failure, and transferring the results to a model for more accurate failure determination. Acknowledgements The results presented here were obtained within a research project funded by the Deutsche Forschungsgemeinschaft e.V. (DFG) with the project number 459023912. Further thanks go to the Institute for Materials Testing, Materials Science and Strength of Materials (IMWF) of the University of Stuttgart for the successful cooperation, to TerHell GmbH for providing the test materials and to the students Joachim Bräutigam and Marius Reitinger for their work in the context of their theses. References [1] Bonten, C. Kunststofftechnik. Einführung und Grundlagen. 3. Auflage. München: Hanser, 2020. ISBN 978-3-446-46471-1. [2] Gross, D. Bruchmechanik. Springer Berlin Heidelberg, 2016. ISBN 978 – 3 – 662 – 46736 – 7. [3] Rice, J. R. A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks. In: Journal of Applied Mechanics 35, 1968. 2, S. 379 – 386. DOI: 10.1115/1.3601206. – ISSN 0021 – 8936. [4] Cherepanov, G. P. Crack propagation in continuous media. In: Journal of Applied Mathematics and Mechanics 31 , 1967. 3, S. 503 – 512. DOI: 10.1016/0021 – 8928(67)90034 – 2. – ISSN 00218928. [5] Begley, J.; Landes, J. A comparison of the J-integral fracture criterion with the equivalent energy concept. In: Progress in flaw growth and fracture toughness testing . ASTM International, 1973, DOI: 10.1520/stp49644s, S. 246 – 263. [6] Döll, W. Application of an energy balance and an energy method to dynamic crack propagation. In: International Journal of Fracture , 1976, 12(4), S. 595-605. [7] Swallowe, G. Measurements of transient high temperatures during the deformation of polymers. In: Journal of materials science , 1986, S. 4089 4096. [8] Rittel, D. Experimental investigation of transient thermoplastic effects in dynamic fracture. In: International Journal of Solds ans Structures , 1998, (37), S. 2901-2913. [9] Li, Z.; J. Lambros. Strain rate effects on the thermomechanical behavior of polymers. In: International Journal of Solids and Structures , 2001, (38), S. 3549-3562. [10] Hadriche, I., et al. Influence of strain rate on the yielding behavior and on the self heating of thermoplastic polymers loaded under tension. In: Key Engineering Materials . Trans Tech Publications Ltd, 2010. S. 63-72. ISSN 1662-9795. [11] Lisle, T., et al. Measure of fracture toughness of compressive fiber failure in composite structures using infrared thermography. In: Composites Science and Technology , 2015, 112. Jg., S. 22-33.