Investigation and statistical analysis of the mechanical, thermal and physical properties of nanogelcoat coated glass fiber reinforced polymer composites after aging

Fiber-reinforced polymer composites are more preferred than conventional composites due to their high strength and lightness properties. These composites, which are preferred in marine applications due to their ease of assembly, repair and production, are exposed to environmental conditions. Despite having exceptional properties, their expected lifetime is reduced when exposed to environmental conditions such as ultraviolet radiation (UV), freeze/thaw cycles, or variable hydrothermal conditions. In order to minimize these effects and optimize their lifetime, gelcoat coating is applied to fiber-reinforced polymer composites. Gelcoats are especially used for glass fiber reinforced polymer (GRP) composites to improve surface quality and performance against environmental conditions. The most commonly used gelcoats are thermoset polymers based on epoxy or unsaturated polyester. In the literature, there are studies on the subject of increasing the resistance properties of GRPs against environmental conditions by coating them with classical gelcoats. Although the expected lifetime of FRPs is increased with this method, composites with longer lifetimes are needed. It is known that the mechanical and barrier properties of nanoparticle-doped gelcoats are better than traditionally used gelcoats. However, there are very few studies on the use of nanoparticle-doped gelcoats in coating applications for composites, especially for GRPs used in maritime areas, and how this coating will protect the composite material from environmental conditions.In this study, the surfaces of glass fiber reinforced epoxy composites were coated with nanoparticle-doped gelcoats and their resistance to harsh environmental conditions was tested. The reason for choosing glass fiber for the study is that the material and production cost is low and it is widely used in the marine applications. Titanium dioxide (TiO2) and nanoclay, which are known to have positive contributions to gelcoat in the literature, were used as nanoparticles. Spray coating method was preferred as the coating method. Composites were exposed to freeze/thaw cycle and variable hydrothermal conditions, and then the effects of these factors on the mechanical properties of the composite material were investigated. Mechanical tests are tensile test, bending test, compression test and interlayer shear tests. Thermal tests are Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA) tests. After the tests, the relations between the experimental results and the meaning relations were evaluated statistically by ANOVA analysis. As a result, it was determined that nano TiO2 increased both the mechanical and thermal protective properties of the composite material, but the nanoclay decreased it.