PSI - Issue 60

Rajagurunathan and Prakash./ Structural Integrity Procedia 00 (2024) 000–000

Rajagurunathan M et al. / Procedia Structural Integrity 60 (2024) 517–524

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force approached its peak value, which denotes matrix damage. But in cases with high impact energy (41.6 J and 65 J) more oscillations were seen close to the maximum force, and later an abrupt force reduction with the appearance of fiber breakages. The impact durations for low and moderate impact levels were observed as almost identical. But for high impact energy cases, longer duration was noted due to damages to matrix and fiber along with delaminations. 4.2. Absorbed energy-time histories The energy absorbed-time histories of cross-ply and quasi-isotropic laminates are depicted in Fig. 7. From the numerical results, it was found that the energy absorbed by the cross-ply laminate (0/90) 2s is higher than that of quasi-isotropic laminate (0/45/-45/90) s at low energy impact (2.6 J and 10.4 J). For moderate impact energy level (23.4 J), the energy absorbed by both laminates are almost similar. Also, the laminates are damaged by the combination of delamination and matrix damages at this energy level. But in high energy impacts (41.6 J and 65 J), the damages are formed due to delamination, matrix cracking and fiber damages. The energy absorbed by the QI laminate is 5.2% higher than the cross-ply laminate at 65 J and 9.1% higher at 41.6 J.

a) b) Fig. 5. Propagation of delamination at 10.4 J and 65 J energy levels for laminates: a) (0/90) 2s ; b) (0/45/-45/90) s .

a) c) Fig. 6. Impact force (N) vs time (s): a) (0/90) 2s ; b) (0/45/-45/90) s ; c) Impact force (kN) vs Impact velocity (m/s). b)

a) c) Fig. 7. Absorbed energy (J) vs Time (s) on laminates: a) (0/90) 2s ; b) (0/45/-45/90) s ; c) Percentage energy absorbed. 5. Conclusions A numerical investigation using ABAQUS® Finite Element method on the low velocity impact behavior of CFRP laminates was conducted to predict the impact resistance and visualize the damage mechanisms. The intra laminar damages were found by Hashin 2-D criterion. The delamination between plies were obtained by cohesive surface model which is based on traction-separation law. The effect of impact velocity on cross-ply and QI laminates was studied and the results were compared in terms of delamination area, fibre damage, energy absorbed and force-time histories. The following conclusions are drawn from the numerical investigation: b)