Research In Preparing Superhydrophobic Microstructure For Aircraft Prevent/de-icing

Icing has a ngative effect on the flight performance of aircraft. At present, the prevent/de-icing technology for the aircraft surface is not only complex but also high cost, in addition it is not good for improving the and can affect the pneumatic performance of the aircraft.Therefore, exploring new anti/de-icing technology is very important for manufacturing big plane.Based on analyzing the hydrophobic structure on the lotus and other plant surfaces, the hydrophobic technologist realized by chemical modification of surface microstructure with low surface energy nano-material. Surface micromachining and modification do not change the pneumatic structure of aircraft.It also does not need to add any specialized de-icing mechanism appliance in the structure design of the fuselage. The application of the super-hydrophobic surface in the aircraft will retard the aircraft icing phenomenon to a great extend.In this paper, the feasibility of using microarray structure to improve hydrophobic performance is simulated.Microarray units with various shapes and sizes was prepared and their hydrophobic performancesare test. At the same time, the bond strength between the microarray and the substrate is measured and compared.First of all, the different collision situation between the droplet and underside are simulated through using fluent software. The results indicate that the bottom contact angle, themicrostructureon the substrate, the height of water droplets before fallingand incline angle of the substrateare key factors affecting the rolling of water droplets after it contact with the bottom. The results show that producing microstructureon material surface can effectively improve the hydrophobicity, providing guidance for subsequent experiment.On the basis of the above simulation, the preparation of microstructure on thematerial surface and the testing of the hydrophobic performance are carried out. It is found that material itself and the surfacemicroscopic are the main factors for the hydrophobic performance. The contact angle of commonly used material for the plate is generally less than 100 °. Preparation of micro array structure on material surface can effectively improve the ontact angle to around 140 °. For the cylindrical 5-15 array,the contact angle is up to 151.4 °, which realized the superhydrophobic performance. Contact angle changes with the array size, verifying the Cassie theory, which realizes the three-phase contactof solid, liquid, and gas, and will gradually shift to Wenzel model.The bonding strength between coating microarray and base material can be affected by heat treatment and the property of base material. The highest bonding strength of aluminium and composite material base is only 70 Mpa. Heat treatment at 200°C can improve bonding strength of Ti plate from 195 Mpa to 354 Mpa.There are two major factors that impact bonding strength between base material and coating.The first is the nature of backing material itself as well as its atomic bonding method.When the combination is metallic, the bonding strength between coating and substrate is significantly greater than that by van der Waals force.The second is the surface roughness of base material as well as diffusion between base material and coating.The material surface roughness is measured by AFM.The result shows that only when the roughness is large enough and uniform, large bonding strength can be obtained. The fracture morphology of the basal material after the coatingpeeling isobserved by SEM and EDX measurement.Under the high temperature for a long time, the diffusion can become quite thick and a thick diffusion is formed. The space between the coating and the substratedecreases,which is more advantageous to form metallic bond, thus improving bonding strength between coating and base material.