Impact of Thermal Cycling on Carbon Fiber Reinforced Glass Epoxy Laminates
Burugula, Lakshmanaomkara Subhadra
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Wind Turbine blade icing is a serious problem in cold climates, which leads to production losses, failure of the blade, ice throw etc. To eliminate production downtime associated with icing of wind turbine blades, a structurally integrated, carbon fiber based wind turbine blade heating system has been proposed. The de-icing of the blades, where the carbon fiber element is heated which results in a temperature gradient across the blade which may compromise the structural properties of the material. This is explained by the uneven thermal expansion of the different components in the composite (blade) material. Due to the micro-cracking in the composite material it leads to deterioration of the material which further leads to failure. There is a need to investigate the effects of thermal cycling on the structural properties of the composite material. The two main parts of this thesis include the thermal cycling of the CF reinforced glass epoxy laminate samples and Flexural testing on the thermal cycled samples. Thermal cycling is performed on CF reinforced glass epoxy laminate samples with a range of -18 °C to 4 °C with a hold time of 10 minutes for each heating/cooling cycle. A set of 6 samples were taken for each thermal cycle and ran 0, 50, 100, 200 thermal cycles. Temperatures of the samples were recorded using the computer program as well as pictures were taken using a thermal camera; from this data it shows that there is a considerable temperature difference between the carbon fiber and side thermocouples. To study the effects of this temperature gradient on the flexural properties of the laminate, on all the samples three point bending tests (following ASTM standards) are performed and examined for any change in the properties with the increase in the number of thermal cycles. Test results showed that there is very little decrease in the ultimate stress when numbers of thermal cycles were increased from 0 to 200; this decrease is not significant to affect or degrade the material properties of the sample. There might be an effect on material properties when thermal cycling is done in higher levels with more thermal cycling temperature range.