PSI - Issue 14

T Sreekantha Reddy et al. / Procedia Structural Integrity 14 (2019) 265–272 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Fibre breakage area and delamination area of all the laminates impacted at different energies are given in Fig.6. As the thickness is increased fibre breakage area is reduced at all the impact energies, for instance, fibre breakage areas for 3mm, 5mm & 7mm thick laminates are found to be 6.74, 5.75 & 2.15 cm 2 respectively when impacted with 100J energy. As expected, for a particular thickness it is increased with increase in the impact energy. Delamination areas are found to be in the range of 5-45 cm 2 for the laminates tested in the impact energy regime as shown in Fig.6(b). As mentioned earlier, no delamination is observed for 3mm laminates at all impact energies. Delamination area also increased with increase in the impact energy. However, unlike fibre breakage area, delamination area did not show any trend with thickness. 5mm laminates show least delamination area as most of the energy is absorbed for fibre breakage. It increased for 7 mm laminate and then decreased for 10 mm laminates. This decrease for 10 mm laminates may be attributed to increased stiffness.

Fig.6. (a) Fibre breakage (b) Delamination and (c) Total damage areas of all the laminates impacted at different energies

3.3.2. IR Thermography IR thermograms that are taken at front and rear side of impacted laminates are presented in Fig. 7. The trend of damage area at rear side is similar to visual observation. However, the quantitative values are found to be higher than that of manually calculated damage areas (Table 3). This suggests that there may be internal debonding between the laminas which is not seen by visual observation. Hence it can be concluded that visual observation is useful to get approximate value of damage areas where as IR thermography is effective tool to obtain more accurate damage areas.

Fig.7. IR thermography images of different thickness laminates impacted at 100J energy