A Comparative Study on Damage Mechanism of Sandwich Structures with Different Core Materials under Lightning Strikes

Abstract

[...]material damage under large current conditions is mainly attributed to the thermal impact and airflow pressure inside the porous materials (PVC, PET and balsa wood), so it is essential to study the temperature and pressure distribution inside the sandwich structure. Comparing Equations (6) and (5) for a solid material, ρgCgu· ∇T was added to describe the heat flux by gas convection from neighboring elements. Since there is gas fraction in the porous materials, heat transfer by gas convection should be included too. Based on the above model, the roles of porosity and permeability were analyzed which helped materials designing for wind turbine blade. Since permeability hardly influenced the thermal conducting and airflow expansion process because of the very small dynamic viscosity of air (see Equation (11)), only results for different porosities will be presented. See PDF.] Materials Type Thermal Conductivity, k, W/(m·K) Specific Heat, C, J/(kg·K) Density, ρ, kg/m3 Glass Transition Degree, Tg, K Solid Fraction θ (%) Epoxy resin SWANCOR 2511-1A/1BS 0.4749 989.58 1200 363 100 PVC 3A C70.55 0.0331 1003 66 355 8 PET 3A T92.100 0.0399 1166 98 340 13 Balsa wood 3A SB100 0.0803/0.0661 1047 92 543 11 Current Peak Value (kA) 6.28 12.56 21 cd md cd md cd md PVC 0.11 0.50 0.35 3.5 1.7 6.10 PET 0.07 0.45 0.21 3.0 1.5 5.50 Balsa wood 0.01 0.75 0.09 4.1 0.39 7.50 Solid Fraction 1 Time 2 Times 3 Times 5 Times PVC 0 22.5 68.7 72.6 PET 0 17.7 70 73.3 Balsa wood 0 30.7 49.3 86.7 Solid Fraction 1 Time 2 Times 3 Times 5 Times PVC 0 2.6 5.1 23.1 PET 0 3.6 22.1 26.3 Balsa wood 0 3.2 20.6 25.9 Acknowledgments This work was supported by the National Natural Science Foundation of China (grant numbers 51420105011, 51677110).