PSI - Issue 53

A. Neto et al. / Procedia Structural Integrity 53 (2024) 338–351 Alexandre de Oliveira Neto / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 10. Tier 2:(a) L2 before permanent damage; (b) L2 at its highest deformation; (c) L2 after impact

Compared to L1, L2 suffers again more in terms of the extension of permanent damage despite less than half impact energy. Coincidently, the damage occurs also up to the 6 th most inboard layer. The layer inflicted damage remains the same between the highest deformation moment and after the impact.

0 1 2 3 4 5 6 7 8

L1 L2

7,51

5,12

3,45

2,41

Total Energy [J]

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6

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Time [ms]

Fig. 11. L1 and L2 total energy-time graph with intermediate damage

Total energy peaks are consistent with the initial inflicted impact energy. L1’s elastic energy is in the region of 32 %, and for L2 is about 30 %. The outlier is L1, where somehow it registered a higher value of elastic energy compared to what happened in Tier 1. The behaviour of the tube layup appears to be nonlinear in terms of elastic energy retention. In other words, the percentage of elastic energy is not directly proportional to the applied energy. Instead, it varies with the magnitude of the impact energy. 3.3. Tier 3: Visible external damage In this Tier, where the layups showcase the most impact energy difference, L1 clearly is able to sustain a lot more for the plastic deformation to be visible to the naked eye. The damage initiation is identical, as can be seen in the initial curve slope. Again, the L1 curve’s behaviour near maximum displacement can be explained due to energy dissipation through the tube during heavy impact. In Tier 3 is where the most damage can be expected. During the impact, the tube rebound is clear and the external visible damage only occurs after the tube hits the impactor itself when recuperating elastically. In this cut view, only