PSI - Issue 14

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

269

5

For instance, if we take the peak force data at 100J impact energy, it has increased by 0.97 times, 1.79 times and 2.67 times for 5mm, 7mm and 10mm laminates respectively over that of 3mm thick laminates.

Fig. 3. (a) Comparison of Force - displacement curves for all thickness laminates at 100J impact energy, (b) Comparison of F max of all laminates at different impact energy

3.2. Energy dissipation & contact duration Fig.4(a), Fig.4(b) Fig.4(c) and Fig.4(d) illustrates Energy-time curves of 3mm, 5mm, 7mm and 10mm thick laminates respectively impacted at three different impact energies. In a typical energy – time curve, peak value gives the impact energy, flat portion gives the absorbed energy (E a ). The difference between these two gives the rebound energy (E r ) or elastic energy in the case of partially perforated samples, where as for completely perforated samples, the difference between peak value and quasi flat value before reaching peak value gives frictional energy (E f ) (Reddy et al., 2016). Contact duration is taken as time at which energy curve become flat after reaching its maximum.

Fig. 4. Energy-time curves impacted at three different energies a) 3mm, b) 5mm, c) 7mm, d) 10mm laminates