## 3 Results
From Figure 2c it is possible to observe that the elastic energy is never equal to zero, which means that the absorbed energy is never equal to the impact energy. Therefore, the penetration threshold was not reached because the excess energy is used to rebound the impactor [42; 43]. In this context, if the elastic energy versus impact energy is plotted and the data fitted by polynomial equations, the penetration thresholds can be determined [19; 43]. Figure 3 shows the methodology used to obtain the penetration threshold for all laminates, and values of 34.5 J and 37.6 J were found for control laminates and cork-filled laminates, respectively. The effect of hostile solutions on the impact strength was evaluated for the energy of 12 J. For each condition, five specimens were used, and the results presented in terms of average values. The influence of the exposure time on the maximum load, maximum displacement and restored energy were analysed and the results shown in Figures 4-6, respectively. In these representations, each result was dimensionless/divided by the respective value obtained with the control specimens (without immersion in any solution). The average results and respective standard deviations will be summarized in form of tables. Therefore. the benefit achieved with the introduction of cork powder in the resin is notorious, which promotes an increase in the penetration threshold about 9% higher than that of the control samples. This is a consequence of the significant amount of energy absorbed by cork associated with the high viscoelastic return [40,41]. A similar benefit was obtained by [PERSON] et al. [19] for Kevlar laminates, when the epoxy matrix was filled with cork powder. In this case, the penetration threshold was around 30.9 J for the control samples, while for laminates with cork powder this value was about 34.8 J, promoting, in this case, a benefit around 12.6%. However, the greatest benefit observed by the authors in relation to that obtained in the present study is due to Kevlar fibres being more tolerant to damage than carbon fibres. Figure 4: _Cont._  
Figure 3: Penetration threshold for laminates with neat resin and matrix filled with cork powder. Figure 4: Influence of solution type and exposure time on the maximum impact load after immersion into: (**a**) diesel; (**b**) H\({}_{2}\)SO\({}_{4}\), (**c**) HCl, (**d**) NaOH, (**e**) distilled water and seawater; (**f**) seawater at room temperature and at 60 \({}^{\circ}\)C.  
Figure 5: _Cont._  
Figure 5: Influence of solution on the displacement after immersion into: (**a**) diesel; (**b**) \(\rm H_{2}SO_{4}\), (**c**) HCl, (**d**) NaOH, (**e**) distilled water and seawater; (**f**) seawater at room temperature and at 60 \({}^{\circ}\)C.  
Figure 6: _Cont._  
From Figure 4, it is possible to observe that, for all harsh environments, laminates with neat resin are much more sensitive to exposure to such solutions than carbon laminates with matrix filled with cork. It is also noticed that the maximum load decreases when the samples are exposed to different environments and this tendency is highly dependent on the exposure time. This evidence agrees with the studies reported in the open literature [24,44,45]. Although the values are always lower than those observed in specimens not exposed to hostile environments, Table 3 also shows that the behaviour of laminates with matrix filled with cork powder always revealed a maximum impact load lower than that observed in control laminates. For example, comparing the maximum impact load obtained for 30 days of immersion into different solutions and the value obtained for the respective laminates without any degradation (no immersion in such solutions), it is possible to assess the severity of harsh environments in this parameter (maximum impact load). This effect is summarized in Table 4, in which the decrease observed for the different solutions is presented in percentage terms.