PSI - Issue 28

5

N.A. Sazhenkov et al. / Procedia Structural Integrity 28 (2020) 1572–1578 N.A. Sazhenkov et al./ Structural Integrity Procedia 00 (2019) 0 –000

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a)

free edge of the coated specimen reached 30.9 mm and 37.9 mm at the times of 2.48 and 4.44 ms. This is 40% more than for uncoated samples. In the third frame (Figure 4,b, time 2.26 ms), it can be seen that the projectile begins to rebound. The coating prevents the penetration of the sample and the target sample reaches a greater deflection than in the first case. The kinetic energy of the projectile is not spent on the destruction of the sample but is stored in the form of elastic deformation energy and returned when rebounding. Comparison of post-test damage shows the following difference for samples with polyuria coating on the front side and without any coating. At equal collision rates, the delamination area of coated samples is greater, even if no penetration occurred. The delamination area of the sample after the test can be estimated from a photograph b) Fig. 4 – Selected frames of a high-speed collision process (top view) at the speed about 128 m/s: a) target without coating and b) target with polyurea coating on its face

taken under illumination from the opposite side with a bright lamp. The example of such an analysis is presented in Figure 5 for samples № 2 and № 6 (Table 1) tested at the impact speed of about 135 m/s. The delamination zone is indicated by a blue line. For uncoated sample № 2 it is 8079 mm 2 (Fig. 5, a), and for coated specimen № 6 it is 19990 mm 2 (Fig. 5, b). Despite the fact that sample №6 was no t pierced through, and sample №2 was pierced, the area of damage in sample №6 is twice as large . The use of a protective polyurea coating resulted in the delamination surfaces extending to the lateral boundaries of the specimen (Fig. 5, b). This is consistent with the fact that the presence of a coating increases the displacements at the 2nd

a) b) Fig.5 – Comparison of delamination zones for: a) sample №2 without coating; b) sample №6 with polyurea coating