Investigating the effects of surface superhydrophobicity on moisture ingression of nanofiber-reinforced bio-composite structures

Superhydrophobic coatings have been involved in many industrial applications because they exhibit high water repellency. These coatings can usually improve the surface properties of materials by reducing corrosion, adhesion, deicing, defrosting, and wetting, and increasing self-cleaning. In this study, superhydrophobic coatings were applied on the surfaces of carbon, Kevlar, and glass fiber composites to eliminate the absorption of moisture into the composite structures. The superhydrophobic coatings consist of two coats: bottom (or base) and top. The coated composite coupons were subjected to moisture ingression tests in deionized water until the samples reach their moisture equilibrium, which may vary between 4 and 6 weeks, and then the ingression tests were compared with the bare composite coupons. The water contact angles (WCAs) and thicknesses of the composite samples were measured at the beginning and end of the tests. The moisture gain of all composite coupons was measured as a function of immersion times. Heat treatment tests were performed on the samples to observe the moisture gain. In order to characterize the coated surfaces, WCA tests and Fourier transform infrared spectrometry analyses were also conducted. Test results demonstrated that when the surface of composites was coated with superhydrophobic coatings, the moisture absorption was much less in comparison to the non-coated composite coupons. This study can provide several benefits to the composite industry in general, and the aircraft and wind turbine industries in particular, in terms of moisture elimination, weight savings, and structural integrity of composites.