## 3 Experimental Investigations
### Results  
Full wavefield images obtained at t = 108 \(\upmu\)s, for three different specimen conditions (without damage, with 8 J impact and with healed 8 J impact and 5 J impact), are presented in Figure 11. It may be noted that the 8 J impact causes significant wavefront distortion at the impact area (Figure 11b) and after the curing process (Figure 11c).  
The second damage scenario (5 J) produces much smaller wave distortions at impact area in the central top part of the wavefront. (Figure 11c).  
Based on measurements of these three scenarios, simple energy maps of propagating Lamb waves (based on RMS of raw data) were prepared and are presented in Figure 12.  
It may be noted that raw RMS maps reveal changes in an energy distribution corresponding to the particular damage scenario. Exactly on the impact area, the energy is increased due to wave entrapment in the delaminated region. Behind BVIDs (from incident wave point of view), interference patterns are visible.  
Figure 10: Specim with barely visible impact damage (BVID): (**a**) 8 J scenario; (**b**) 5 J scenario.  
However, raw RMS maps are difficult to interpret, and it is inconvenient to give a quantitative value for damage severity based on those results. To overcome this problem, the proposed technique for extracting the information about wavefield changes was used. Obtained damage maps for three damage scenarios are presented in Figure 13. For comparison purposes, damage maps obtained with additional attenuation compensation are also presented in Figure 14. Additionally, close up pictures of the damaged region at three different time moments after the impact are given in Figures 15 and 16 for 8 and 5 J impact areas, respectively.  
It may be concluded that 8 J impact is detected with its size, shape and severity on both damage maps. The second impact scenario is hardly noticeable, so it is on the limit of this method.  
Figure 11: Full wavefield images in space-space domain captured at t = 108 \(\upmu\)s: (**a**) pristine condition; (**b**) 1 h after 8 J impact; (**c**) 1 h after 5 J impact.  
Figure 12: RMS maps: (**a**) pristine condition; (**b**) 1 h after 8 J impact; (**c**) 1 h after 5 J impact.  
Figure 14: Damage maps with attenuation compensation: (**a**) pristine condition; (**b**) 1 h after 8 J impact; (**c**) 1 h after 5 J impact.  
Figure 13: Damage maps: (**a**) pristine condition; (**b**) 1 h after 8 J impact; (**c**) 1 h after 5 J impact.  
Based on all data processed, the energy at damage area is presented (Figure 17) as a function of time (\(T\)), where \(T=0\) stands for the moment of impact. The results are put together with reference signals.  
Figure 16: Close-up of BVID (5 J) region (**a**) 1 h, (**b**) 6 h, (**c**) 29 h after the moment of impact.  
Figure 17: Total damage map energy at impact region: (**a**) 8 J scenario; (**b**) 5 J scenario.  
Using obtained energies for tested and reference states, relative damage severity was estimated (Equation (10)) and is given in Figure 18. It may be concluded that the self-healing process has exponential-like character, and most of the healing is realized during first 20 hours. In the case of 8 J impact, the rate of the healing was estimated to be around 20%, while at lower energy impact (5 J) it was estimated to be around 40%.