PSI - Issue 47

Johannes Wiener et al. / Procedia Structural Integrity 47 (2023) 253–260 Johannes Wiener/ Structural Integrity Procedia 00 (2019) 000–000

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(a) (b) Fig. 6. (a) Overview of investigated multilayer architectures, which were assessed regarding their relative fracture toughness, Ω , and specimen stiffness, E eq , and (b) evolution of the plastic zone during SENB testing of composites with PP-St ILs (reprinted with permission of (Wiener et al. 2022) and (Wiener 2023)). 4. Conclusions It was attempted to replicate the crack arresting properties of biological materials using layered polymer composites with talcum reinforced PP as matrix and softer grades of PP as interlayers (ILs). For composites with micron-sized layers, the matrix layers should be as small or smaller than the largest inherent defects in order to maximize impact strength. Although increases in toughness up to 400% can be achieved this way, specimen stiffness was also found to suffer. Reductions up to 90% were observed as a result of stress decoupling effects between the layers. It should be noted though, that the increase in toughness outweighed the stiffness reduction. For composites with a smaller number of millimeter-sized layers, the reduction of stiffness was not as severe. For a very soft IL material (PP-Soft), 50% of matrix stiffness could be preserved, while the relative fracture toughness was increased by 105%. Stiffness reduction was avoided almost completely when using a stronger IL material (PP-St), so that the best-case scenario could boast an increase of fracture toughness by 181% while only sacrificing 6% of matrix stiffness. Acknowledgements Financial support by the Austrian Funding Agency (FFG) within the scope of grant agreement 858562 (acronym ‘BiomimicPolymers’) is greatly acknowledged. Special thanks go to Prof. Otmar Kolednik for most fruitful discussions and his insights in elastic plastic fracture mechanics. References Aizenberg, J., Weaver, J. C., Thanawala, M. S., Sundar, V. C., Morse, D. E., and Fratzl, P. 2005. Skeleton of Euplectella sp.: Structural hierarchy from the nanoscale to the macroscale. Science (New York, N.Y.) 309(5732):275-278. https://doi.org/10.1126/science.1112255. Ashby, M., and Cebon, D. 1993. Materials selection in mechanical design. J. Phys. IV France 03(C7):C7-1-C7-9. https://doi.org/10.1051/jp4:1993701. Barthelat, F., and Espinosa, H. D. 2007. An Experimental Investigation of Deformation and Fracture of Nacre– Mother of Pearl. Exp. Mech. 47(3):311-324. https://doi.org/10.1007/s11340-007-9040-1.