PSI - Issue 28

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

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structures from explosions. In the works of Davidson J.S et al. (2005), Szafran J. et al. (2016), Iqbal N. (2018) [1-3] the application of polyurea coatings for the protection of concrete walls is described. The coating prevents fragments from breaking off on the back side of the wall in the event of an explosion. Some researchers have considered the use of polyurea to improve the blast load resistance of metallic structures. Amini M.R. et al. (2010) [4,5] in experimental and numerical study found that polyurea layer can have a significant effect on the response of the steel plate to dynamic impulsive loads, both in terms of failure mitigation and energy absorption, if it is deposited on the back face of the plate. Dai L. et al. (2018) [6] underwater explosion tests were carried out to investigate the protective effect of thin steel plates coated with the polyurea layer. The authors experimentally found that the coating on the front or back of the plate can provide a significant base steel plate protection with a small increase in surface density. Ackland K. et.al. (2013) [7] describes experiments on blast loading of steel plates coated with polyurea on the rear surface. The mechanism of deformation of such two-layer plate and coating delamination was studied. Application of a polyurea coating for explosion protection of structures made of composite materials has been described in several studies. Bahei-El-Din Y.A.et al. (2006) [8] examined a sandwich consisting of two layers of laminate separated by a layer of foam. A thin layer of polyurea is inserted between the laminate face layer and the foam. It changes the spread of stress waves and reduces the damage dealt to the sandwich under blast loading. Tekalur S.A. et al. (2008) [9] applied the polyurethane coating to protect GFRP under explosive load. The results showed that adding a layer of polyurea on the impact surface significantly increases impact resistance. In addition, sandwich materials constructed by placing polyurea between two composite casings had better impact resistance than multi-layer and composite plates. LeBlanc J. et al. (2014) [10] described an experimental and numerical study to evaluate the response to an explosion under water of polyurea-coated GFRP plates. The transient response of the plates is recorded using a digital image correlation system. Polyurea coatings located at the back of the panels were found to provide better performance than when they were located on a front surface. The positive effect of polyurea coatings was found for the case of piercing the metal plates with a steel projectile. Xue L. et al. (2010) [11] found that the V50 ballistic limit for the pointed projectile increases by 42% from the blank steel plate to the polyurea backed plate. Cai et al. (2015) [12] successfully used a polyurea coating to increase resistance to punching of tanks for toxic liquids. Mohottia et al. (2014, 2015) [13, 14] investigated resistance to penetration of polyurethane coated aluminum plates with a steel projectile. The polyurea coated plates showed a considerable reduction of deformation when compared to the uncoated plates. At high projectile velocity, the coating increases the ballistic limit and reduces the residual projectile velocity. The above brief review of the studies leads to the following conclusions. The polyurea coating increases the resistance of structures to explosive loading and penetration by projectiles. The reasons for this effect have not been fully investigated. To solve practical problems of designing structures with coatings it is necessary, in particular, to study different variants of material and thickness of target plates and coatings. The purpose of the present work is to obtain experimental data on high-speed impact of fiberglass (GFRP) layered plates with different variants of polyurethane coating location. 2. Experimental Study

The idea of the experimental study is to determine the ballistic limit of GFRP plates with and without polyurea coating under conditions of high-speed impact with a steel projectile. 2.1. Investigated materials and samples The GFRP samples (Fig. 1) were made from 42 layers of fiberglass weaved fabric with an epoxyphenol resin matrix. The thickness of one layer is about 0.2 mm. Samples in the form of a rectangular plate with a size of 200 mm × 300 mm have a total thickness of 8.4 ± 0.1 mm with a mass of 0.925 ± 0.005 Kg. The material density is 1825.57 Kg/m 3 , the areal density is 15.42 Kg/m 2 . A total of 11 samples were

Fig. 1 – Glass fiber reinforced laminate