PSI - Issue 34

Alexander Berndt et al. / Procedia Structural Integrity 34 (2021) 105–110 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Table 1 shows the average values of maximum force, average force, CFE and the SEA of each set. The first set with a 15 ° fiber angle layup has the best crush force efficiency. Whereas the set with a 75 ° setup has the lowest average SEA value, despite the fact, that one of the specimens withstood a maximum force of F max = 20 kN. One of the possible explanations is that during the printing process the interlaminar adhesion between each layer was better. And that there were less cavities and voids between each layer. Further investigation regarding consolidation of the specimens during or after the printing process is needed.

Table 1. Average results of quasi-static compression tests of CCF crash tubes; average of SEA is shown. Fiber angle (°) ��� �� �� � (N) �� �� �� � (N) ��� �� � (-) �� ��� � (kJ/kg) 15 15828,6 11362,9 0,71 65,4 30 14438,6 10525,1 0,60 61,2 45 14134,4 8526,2 0,60 49,8 60 14926,4 9014,0 0,61 53,3 75 16200,6 8284,7 0,52 49,2

4. Conclusion To summarize, the possibility of printing on a fourth axis has been shown. Therefore, a modular fourth axis was implemented into an existing opened Markforged MarkTwo 3D printer. This additional axis can be implemented into any existing 3D printer with an open-source mainboard. The optical analysis of each specimen exceeded the expectations. There were no voids between the layers on the outside. For a better qualitative analysis, a CT scan is recommended. Furthermore, the energy absorption capability of different fiber aligned CCF crash tubes has been determined. It was shown, that by adding an additional axis the possibilities of the FDM can be extended. Firstly, it follows that there are even more reserves in the manufacturing process and secondly, that there are more possibilities by arranging the fiber angle of each lay-up matching the load direction. Further research needs to go into the specifics of petal forming of 3D printed cylindrical structures and the adhesion between each layer. This means that not only a load-directional design of the CCF tubes is useful, but also regarding crack propagation and fatigue behavior need to be taken into consideration.