## 3 Results
### Quasi-Static Testing
For the hybrid, maximum displacement is reached if F < 0.1 F\({}_{\text{max}}\). contrast, which means that the first thermogram is subtracted from each of the following thermograms. In conclusion, a difference in the surface temperature distribution can be seen as contrast. At failure, the crack can be observed as a rectangular-shaped heat flash by the thermography camera. The emission of heat at 23 \({}^{\circ}\)C (see Figure 5a left specimen) lies at about 3-4 \({}^{\circ}\)C, which is about the same for 60 \({}^{\circ}\)C (see Figure 5a right specimen). Comparing all the PPA-GF30 specimens, it can be concluded that no temperature differences at the crack can be measured between 23 and 60 \({}^{\circ}\)C.  
The heating of the CFRP specimens seen in Figure 5b is up to 11 \({}^{\circ}\)C, thus higher than the heating of the PPA-GF30 specimens. There is also no evidence that the heat released by the crack is vastly different for 23 \({}^{\circ}\)C and 60 \({}^{\circ}\)C in CFRP. In situ thermography on the hybrid specimens is represented in Figure 6 The thermograms 1-8 show the hybrid at specific damaging events during the tests. Note that the white and black dotted lines indicate the position of the insert. In the first four images the thermograms of the quasi-static test at 23 \({}^{\circ}\)C are depicted. Picture 1 in Figure 6 shows clearly visible damage, resulting in a crack directly below the aluminium insert. The temperature rises up to 5.5 \({}^{\circ}\)C at the crack, which lies right in between the values for PPA-GF30 and CFRP. Initial damage in form of cracking or delamination below the insert can be observed for all hybrid specimens. Afterwards, more delaminations and cracks arise (green contrast in pictures 2-3) until most of the area around the insert is damaged. Those delaminations and cracks raise the temperature by 2-5 \({}^{\circ}\)C. In  
Figure 5: \(\Delta\)T-thermograms of (**a**) the PPA-GF30 specimens at 23 \({}^{\circ}\)C (**left**) and 60 \({}^{\circ}\)C (**right**) and (**b**) the CFRP specimens 23 \({}^{\circ}\)C (**left**) and 60 \({}^{\circ}\)C (**right**) in quasi-static testing. picture 4 (see Figure 6), a light blue contrast (@T = 1 \({}^{\circ}\)C) on the right side around the insert shows the final delamination. This encloses the damaged area of the hybrid specimen. Ultimately, the delamination leads to an opening of the CFRP \"bag\", and the insert gets pulled out of it. For the tests at 60 \({}^{\circ}\)C, the first delamination also starts below the insert (see picture 5 in Figure 6) without cracking. Thereafter, the contrast between insert and CFRP laminate increases as delaminations come up (see picture 6 in Figure 6). This also happens at 23 \({}^{\circ}\)C but with a much lower contrast, because less thermal energy is available. Thus, less infrared radiation is emitted. In the following pictures 7 and 8, it seems that colder areas show up. The dark blue spot in the bottom right indicates a small crack where the PPA-GF30 insert gets pushed out. The negative temperature difference could result due to a macroscopic hole in the specimen that reveals the colder background. The black area at the upper end of the thermogram is a consequence of the movement of the specimen in the tensile testing machine and its impact of the difference image. In addition, contrary to [15], the inversely proportional relation between delamination size and surface temperature could not be verified.