PSI - Issue 14

P Rama Subba Reddy et al. / Procedia Structural Integrity 14 (2019) 676–683 Author name / Structural Integrity Procedia 00 (2018) 000–000

680

5

3.2. Effect of matrix on fracture energies Mode-I fracture energies (GIc) have been calculated at different displacements and the data is presented in Fig.3. It is observed that at initial displacements the laminates have shown no difference in fracture energy. It is also to be noted that at initial displacement from 50mm to 55mm did not show any significant energy absorption due to the presence of pre-delamination which was created during the specimen preparation. Hence fracture energies upto 55mm displacement is not reliable and may be erroneous also. However after 55mm displacement the fracture energies have gone up significantly, at 60mm displacement the fracture energy is 0.4 to 0.5 KJ/m 2 and as the displacement progresses, the fracture energy required for the delamination also has increased gradually. From the test data, it is observed that E-glass/epoxy laminate has shown higher fracture energy than E-glass/phenolic laminate. At 70mm displacement E-glass/phenolic laminate has shown fracture energy of 0.7 KJ/m 2 and further increase of displacement has shown no change in fracture energy. While in the case of E-glass/epoxy laminate the fracture energy is 1.3 KJ/m 2 for 70 mm displacement which is almost double when compared to the phenolic based laminate and after 75mm displacement the fracture energy for later also found to be constant. The data suggests that E-glass/epoxy required more energy to undergo delamination this may be due to strong interfacial bond between epoxy resin and reinforcement .

Fig.3. Mode-I fracture energies of E-glass/phenolic and E-glass/epoxy composite laminates

3.3. Ballistic performance of the laminates

Fig.4. Energy absorption of laminates under ballistic impact

Energy absorption under ballistic impact test was determined for both the laminates. Change in energy absorption with increase of laminate thickness at impact velocity of 720±15 m/s is shown in Fig.4. From the data it is seen that both the laminates have shown similar performance at lower thickness (<15mm) which indicates that at