## 3 Results  
The benefits obtained with cork powder were evaluated by impact tests carried out for different impact energies. Figure 1 shows typical load and energy versus time curves of control samples and laminates with resin filled with 3% of cork powder tested for an impact energy of 2 J. \begin{table}
\begin{tabular}{c c} \hline \hline
**Solutions** & **Immersion Time (Days)** \\ \hline Diesel & 15, 30 and 45 \\ Sulphuric acid (H\({}_{2}\)SO\({}_{4}\)), pH = 1.5 & 10, 20 and 30 \\ Hydrochloric acid (HCl), pH = 1.5 & 10, 20 and 30 \\ Sodium hydroxide (NaOH), pH = 13.0 & 10, 20 and 30 \\ Distilled water & 15, 30, 60 and 90 \\ Seawater at room temperature & 15, 30, 60 and 90 \\ Seawater at 60 \({}^{\circ}\)C & 15, 30 and 45 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Different solutions and immersion times used in this study. Figure 1: For an impact energy of 2 J, typical: (**a**) load versus time curves; (**b**) energy versus time curves. Regarding the maximum load (Figure 2a and Table 2), and regardless of the impact energy, it is possible to observe higher values for composites with neat resin than for composites with resin filled with cork powder. On the other hand, for both laminates, higher impact energies promoted higher maximum loads up to 12 J, after which the maximum impact load seems to remain constant. While the maximum load increased around 56.4% between 2 J and 12 J for composites with cork powder, this value was about 102.6% (around twice higher) for composite laminates with neat resin. In fact, literature reports that the maximum load increases with increasing impact energy [16; 19; 31; 37], and this trend can be observed in this study up to 12 J for both laminates. According to [PERSON] et al. [38] the differences observed in the maximum loads are a consequence of the different failure modes introduced in the laminate and, in this context, it is possible to note that for impact energies higher than 12 J the severity of the damage is so significant that the effect is not visible in terms of maximum load. Similar behaviour was observed by [PERSON] et al. [37], as well as the non-linearity also observed in Figure 2a and that according to [PERSON] et al. [39], the maximum load should increase almost linearly with the increase of the impact energy. This parameter is controlled by the impact energy and reflects the maximum load that the composite laminate can tolerate before severe damage occurs [37]. The benefits obtained with the cork powder and respective influence of impact energy on the displacement is shown in Figure 2b and Table 2. Independently of the impact energy, the average results show that laminates with cork powder have the highest displacements. For the studied energy range, for example, displacements increased around 298% and 476% for laminates with neat resin and laminates with epoxy filled by cork powder, respectively. Consequently, as shown in Table 2, the contact time is higher for laminates with cork powder. Under compressive loading during the impact, when cork deforms, the cell walls bend and buckle and can undergo large strain deformation. Therefore, this explains the higher displacements and the lowest maximum loads observed in composites that incorporate cork powder. On the other hand, when cell walls bend and buckle, they can absorb large amounts of energy with high viscoelastic return. This means that, after an impact, the capacity of the cork to continue to absorb energy is almost unchanged due to its elastic deformation [40; 41]. The benefits reported are expressed in Figure 2c, where the lower restored energy to laminates with cork powder is a consequence of the higher energy absorption capacity. For carbon/epoxy laminates, it is possible to observe a decrease in the elastic recovery around 53%, between 2 and 8 J, but this value drops drastically to 77% between 2 and 24 J. When the cork powder is added to the resin, the behaviour is similar, but in this case with values around 68% and 84%, respectively.