## 4 Discussion  
The blunt striker did not cause any visible damage in the reinforcing layers, however, the area of delamination was largest between analyzed cases. As mentioned, the delamination process absorbs part of the impact energy. The main part of the energy difference between the initial kinetic energy of blunt striker and the kinetic energy after its rebound is connected with the energy absorbing delamination process. Including the phenomenon of delamination in numerical studies allows the scientist to estimating the extent of the structure damage. It should be remembered that not every  
Figure 16: Diameters of delamination areas between reinforcement layers 1 and 2 and 13 and 14.  
damage that was caused is immediately visible, as was the case of a panel impacted by the blunt striker. The reinforcing material was not damaged, however, the composite structure was damaged, which affects its strength. The same fact applies to cases in which other strikers were used. As shown by numerical research, the real areas of damage were much larger than that estimated on the diameter of the cavities formed after impact in experimental research. Experimental research presented in another paper [68] confirms that the delamination area grows with each next reinforcing layer from the impact point. The shape of the delamination areas was also similar to the shape that could be observed in experimental research [22]. It is worth to noting that delamination areas can be reduced by adding, for example, nanofibers. Research presented in another paper [62] showed that the incorporation of polycaprolactone nanofibers reduces the delaminated area by about 27% in glass fiber reinforced polymer composites. Research presented in another paper [62] also confirms that the epoxy glass composites reinforced with polycaprolactone nano fibers are less susceptible to impact damage than the same composites without polycaprolactone nano fibers. The comparison of rebounded energy value in the case of conical and ogival strikers with damages caused by those strikers in composites suggests that the energy was absorbed in different ways, depending on the strikers' geometry. Rebounded energy was the same, but damaged was different. In the case of the conical striker, damage in reinforced layers was bigger. In the case of the ogival striker, the delamination areas was bigger, which suggests that the delamination absorbed a higher part of the impact energy than in the case of the conical striker, which causes the smallest damage in the reinforcement layers. In the case of the composite made from glass fibers and polyester resin [69], it was noted that the largest areas of damage were obtained when the conical and hemispherical strikers were used. In the conducted research, the largest diameter of damage in the first reinforcing layer was also noted for these two strikers. In the case of the research presented in a further paper [69], the composite material absorbed different amounts of the impact energy depending on the striker geometry. The amount of absorbed energy in descending order was as follows: conical striker, ogival striker, hemispherical striker, and blunt striker. The same results were obtained for carbon epoxy composite (impact energy up to 6 J) in another paper [70]. In the conducted numerical research, the same order was observed (Figure 9). Carbon fiber reinforced composite in the case of the blunt striker impact (50 J of the impact energy) absorb almost the same amount of impact energy as in the case of the conical striker [45]. In the conducted research, the hybrid composite absorbs different amounts of impact energy in the case of those strikers. In the case of the conical striker, the composite absorbs a few times more impact energy than in the case of the blunt striker.