Investigating the effects of surface superhydrophobicity on moisture ingression of fiber-reinforced laminate composites

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Kasaragadda, Shravani
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The main purpose of this study was to investigate the effectiveness of Superhydrophobic coating surfaces on fiber-reinforced laminate composites. Unlike other structural materials, polymeric materials can absorb more moisture or solvents from the environment, which in turn can affect the mechanical, thermal, and physical properties that decrease the service life of the components. Due to the presence of water in the composite structures, the polymeric matrix goes through a plastification phase (aging). During the transport hydrolysis or chemical aging, the polymer can be drastically damaged or degraded. In order to eliminate the moisture absorption or gain into the composite structures, superhydrophobic coatings were applied to the polymeric composites of Carbon, Kevlar, and Glass. The composite coupons with 2.5x2.5x0.2 cm dimensions were coated with the bottom and bottom + top coats and the coupons were subjected to the moisture ingression tests until the samples reach their moisture equilibrium, which may vary between four to six weeks, and the ingression tests were performed along with the bare composite coupons in separate DI water. The water contact angle values and the thickness of the composite samples for the bare, bottom, and top coat were measured at the beginning and at the end of the tests. The moisture gain of all the composite coupons was measured as a function of immersion times. In this research, three tests—Dipping, Spraying, and Heat Treatment—were performed on the samples to observe the moisture gain in the samples. To characterize the coating surfaces Contact Angle tests, UV Chamber results and FTIR Analysis were performed. The results clearly showed that when the surface of composites were coated with Superhydrophobic coatings, the moisture absorption and the thickness were much less when compared to the bare composite coupons and in all the tests; the Heat Treatment had absorbed less moisture when compared to other tests. This study can provide several benefits to the composite Industry in general and Aircraft Industry in particular, when there was a need for high strength and low weight, to eliminate or minimize the moisture from the composite materials.

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
Wichita State University
Copyright 2016 Shravani Kasaragadda
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