PSI - Issue 52
Quaiyum M. Ansari et al. / Procedia Structural Integrity 52 (2024) 122–132 Quaiyum M. Ansari/ Fernando Sánchez/Luis Doménech-Ballester/ Trevor M. Young / Structural Integrity Procedia 00 (2019) 000 – 000 9
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mm thick. Because the coupon holder in the WARER rig does not allow the test coupon to move radially outward during testing, the coating system is constrained at the circumference. In this study, a coating system is analysed. The LEP coating system generally consists of LEP as the top layer followed by primer, filler and substrate.
Fig. 10. Illustration of LEP coatings system. LEP (gelcoat) material properties are = 1150 kg/m 3 , = 2500 MPa and = 0.4. Similarly, the material properties of the filler are = 1452.8 kg/m 3 , = 8000 MPa and = 0.3, while the material properties of the AL substrate are = 2820 kg/m 3 , = 70 GPa and = 0.3. For this baseline study, the primer material is assumed to be similar to the filler material, which will later be modelled with cohesive elements to understand the interlaminar/bonding strength. Fig. 11 depicts the von Mises stress at the start of the impact when the maximum stress occurs. The stress pattern shows that the stress waves move radially outward from the point of impact and pass through the LEP, primer, filler, and substrate.
(a) (c) Fig. 11. von Mises stress in coating system with 2.0 mm droplet after impact at 100 m/sec with time (a) t = 0.725 µs (b) t = 2 µs (c) t = 3 µs. In addition, von Mises stress and normal stress (S33) have been plotted over time during the impact in Fig. (12). The maximum stress peak of 60 MPa can be seen around 0.725 µs, and then the stress waves move over the material and gradually dampen down over time, reaching nearly zero in 10 µs. von Mises stress is the sum of all normal stresses, whereas S33 is the stress normal to the coating surface, which is the main contributor to von Mises stress. The S33 is a compressive stress that attempts to compress the elements on the coating system during impact, resulting in damage and erosion of the coating system. Finally, it can help determine the failure mode of an offshore wind turbine's leading edge protection coating under rain droplet impact and help to develop a more durable coating considering different failure modes. (b)
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