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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oscillations is reducing with increase in the thickness of laminates which suggests that the resistance of laminate is increasing and thereby reducing the damage. 3mm laminate has completely perforated at 100J energy where as 5mm laminate perforated at 150J. However, 7mm and 10mm laminates remain intact even at 150J impact energy which suggests that perforation energies of these laminates are higher than 150J. This is also evident from the Fig. that max. displacement is increasing with increase in impact energy for all the thickness laminates. For instance, max. displacement of 7mm laminate impacted with 50J energy is 4.8mm and it increased by 54% and 120% when impacted at 100J and 150J, respectively. Maximum displacement has decreased with increase in laminate thickness. Maximum displacement of 7mm and 10mm laminates has decreased about 28% and 50% respectively over that of 5mm thick laminates when impacted at 100J energy.

Fig.2. Force - displacement curves impacted at three different energies a) 3mm, b) 5mm, c) 7mm, d) 10mm laminates

Table 1. Comparison of maximum displacement values at three impact energies Thickness (mm) 50 J 100 J 150 J 3 6.3±0.3 * Test not done 5 6.2 ±0.25 10.3±0.32 * 7 4.8 ±0.18 7.4 ±0.24 10.5±0.4 10 3.4 ±0.11 5.2 ±0.16 7.4±0.32 * complete perforation

Fig.3a gives comparison of Force - displacement curves for all thickness laminates at 100J impact energy. Table 1 gives max. displacement values of all the laminates impacted at three incident energies. Comparison of F max values of 3mm, 5mm, 7mm and 10mm thickness laminates impacted at different impact energies are presented in Fig.3b. Peak force which indicates load bearing capacity of material has increased with increase in impact energy up to the perforation of laminate and became constant. This increment is more visible in the case of 7mm and 10mm thick laminates. When impacted at 50J energy, 5mm thick laminate has shown 13.6 kN peak force. This has increased to 15 kN (10.2%) at 100J and has become constant at 150 J impact energy as the perforation of laminate took place. From the figure it can also be deduced that peak force has increased with increase in thickness at all impact energies.