PSI - Issue 2_A

E. Frutos et al. / Procedia Structural Integrity 2 (2016) 1391–1404 Author name / Structural Integrity Procedia 00 (2016) 000–000

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higher than 10% of the total thickness. Crack length can be measured with each new impact and therefore the correct indentation model for calculating fracture toughness can be selected. This allows studying the evolution of h/a or l/a ratios, as a function of the impacts, i.e. the crack geometry, which evolves from Palmqvist crack (Laugier IM) to half penny crack (Anstins IM). Consequently, it is possible to study the proper evolution of the different values of fracture toughness as a function of different  . Fracture toughness values obtained for W/Cu nano-multilayers, from Anstins indentation model, show an increase from 1.77 ���√� to 1.90 ����√� when the periodicity,  , is reduced from 60 to 30 nm and finally, a decrease until 1.77 ���√� for  =10 nm. Finally, degree of accuracy of fracture toughness values, calculated from a crack induced by repetitive nano-impact tests, using the classic Anstins indentation model has been compared in the framework of fracture toughness mechanics, getting three new K Ic values for these three  . Thus, fracture toughness values increase from 1.82 ���√� to 1.97 ���√������  is reduced from 60 to 30 nm, and then descend to 1.62 ���√� for  =10 nm. These values are to identical to those reported above, which demonstrates that proposed methods are useful to calculate quantitative fracture toughness values in thin nano-multilayers. Acknowledgements The authors wish to express their thanks for the financial support of the European Commission through the project RADINTERFACES (Grant Agreement Number 263273) and the Czech Science Foundation through the project 14 32801P. References Anderson, P. M., Foecke, T., Hazzledine, P. M., 1999. Dislocation-Based Deformation Mechanisms in Metallic Nanolaminates. 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