## 3 Results
### Vertical Weight Drop Tests for Unmodified Panels  
The impact tests were carried out in different energy ranges for a certain number of rebounds, and with the strain gage the maximum deformation of the panel was measured. These results are shown in Table 2.  
Figure 12 shows the sequence of damage to the panels on the impact side, for the different energies tested with vertical weight drop. The sequence allows visualizing the increase in damage that occurs as the applied energy increases. Figure 11: Evolution of flexural stiffness in panel unmodified F up to \(0.27\times 10^{5}\) impact cycles with P = 420 kN/m\({}^{2}\). Figure 10: Normalized damage evolution on unmodified panels. As the impact energy was increased, the microcracks were observed to be oriented in the direction of the fiber. The largest number of observed micro cracks evolved over the 45\({}^{\circ}\) layer. To a lesser extent in the 0\({}^{\circ}\) layer. Impacts less than 40 Joules can be considered low energy, while those greater than 40 Joules high energy, where the panels already show delamination and deep separation of layers. The phenomenon of slamming is a low energy process, for which the panels impacted at 30 J are the best to be considered for comparison with the panels tested in fatigue. When characterizing the panels tested with penetrating inks, it was observed that they had indeed entered the delamination, being easily seen under ultraviolet light. Sections sequentially are exposed to fluorescent light as seen in Figure 13 for impact at 40 Joules respectively, in which interlaminar delamination can be easily observed. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Impact (J)** & **Maximum Deformation (\(\mu\)m/m)** & **\# of Rebounds** \\ \hline
10 & 502 & 1 \\
20 & 749 & 1 \\
30 & 1130 & 1 \\
40 & 1401 & 1 \\
50 & 1710 & 1 \\
60 & 1828 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Variables used in unmodified panels for vertical weight drop tests. Figure 12: Unmodified panels impacted by vertical weight drop test from 10 J to 60 J of energy. Figure 13: Unmodified panel sections exposed to ultraviolet light impacted at 40 J. As expected in a laminated composite material, the breaks in the matrix are vertical and connect with delamination between layers, producing a ladder shape. The breaks observed in the lower layers indicate that the impact energy was converted into damage and was jumping from one layer to another. It is also important to note that according to the orientation of the layers, the delamination moves from left to right starting from the vertical direction of impact. The accelerometer records the acceleration force (G), at a frequency of 104 Hz. According to the suggested equations, they show that the acting force versus displacement has the profiles presented in Figures 14 and 15. The peaks of damage that occurs as the impactor breaks each of the layers. The impactor slows down each time a new delamination occurs. Records the acceleration variations when micro cracks occur in the matrix. In the case of the low energy impact of 30 Joules, the impact force reaches its maximum value by breaking layer 5. Thereafter the layers offer resistance to deformation. In the case of impact at 50 Joules of high energy, the impactor has enough force to continue breaking all the layers until 9 at which it has already bounced. The acceleration curve also allows you to compare how fast laminate damage is and which layers absorb the most damage energy. In the case of the 30 Joule curve, between layers 4 and 5 there is a large increase in damage energy, indicating that this layer broke and delaminated. This is in accordance  
Figure 14: Comparison of the force vs. displacement diagram for an impact at 30 J in unmodified panel. Figure 15: Comparison of the force vs. displacement diagram for an impact at 50 J in unmodified panel. with what was observed in the sections of the material exposed to penetrating ink and ultraviolet light.