A Comparative Study on Damage Mechanism of Sandwich Structures with Different Core Materials under Lightning Strikes
Abstract
:1. Introduction
2. Large Current Experiments
2.1. Experimental Methods
2.2. Results and Discussion
3. Numerical Study on the Temperature and Pressure Distribution
3.1. Simulation Model
3.1.1. Geometry Model
3.1.2. Large Current Source
3.1.3. Heat Transfer in Solids, Porous Materials
3.1.4. Fluid Dynamics in Porous Materials
3.1.5. Multi-Physics Coupling
3.2. Simulation Results
3.2.1. Temperature Distribution
3.2.2. Pressure Distribution
3.2.3. Influence of Porosity, Permeability
4. Conclusions
- PVC, PET and balsa wood all underwent severe damage under a large current, but their damage types were different: PVC and PET suffered serious pyrolysis and cracks inside, while the damage of the balsa wood sample involved fibers breaking off and large delamination at its interface with the resin layer. Balsa wood was burnt only in a little under the experimental current used.
- Porous materials transferred heat much faster than the resin layer, because the fast air-flow convection under the thermal impact from lightning strongly promoted heat transfer in the porous material layer.
- PVC sample had highest average value of temperature and pressure because of its highest air fraction and airflow convection, so it suffered the biggest mechanical damage and chemical damage; and balsa wood suffered relatively less chemical damage because of its higher glass transition temperature. Balsa wood is very soft, which makes it good at reducing the expansion pressure inside, while bad bonding between it and resin layer resulted in large delamination at the interface with the resin. However, when the energy of the lightning current is extremely large, balsa wood usually catches fire more likely than PVC and PET because of its own characteristics, and under the worst conditions, this fire can last for a long time and cause a serious fire hazard.
- If the gas fraction of the porous materials is decreased, that is, the solid fraction is increased, the heat transfer by gas convection in the porous materials can be decreased. Then the damaged area can be reduced and more energy goes out by the current channels to the outside environment in practice. This is a good way to reduce the scale of damage to porous materials under lightning strike conditions.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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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 |
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Yan, J.; Wang, G.; Li, Q.; Zhang, L.; Yan, J.D.; Chen, C.; Fang, Z. A Comparative Study on Damage Mechanism of Sandwich Structures with Different Core Materials under Lightning Strikes. Energies 2017, 10, 1594. https://doi.org/10.3390/en10101594
Yan J, Wang G, Li Q, Zhang L, Yan JD, Chen C, Fang Z. A Comparative Study on Damage Mechanism of Sandwich Structures with Different Core Materials under Lightning Strikes. Energies. 2017; 10(10):1594. https://doi.org/10.3390/en10101594
Chicago/Turabian StyleYan, Jiangyan, Guozheng Wang, Qingmin Li, Li Zhang, Joseph D. Yan, Chun Chen, and Zhiyang Fang. 2017. "A Comparative Study on Damage Mechanism of Sandwich Structures with Different Core Materials under Lightning Strikes" Energies 10, no. 10: 1594. https://doi.org/10.3390/en10101594