Environmental degradation of structured nanocomposites
Naval Postgraduate School Monterey United States
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Epoxy resin nanocomposites are currently being used in multiple structural and multifunctional applications. However, the amount of data known regarding their degradation due to atmospheric conditions UV light, humidity, temperature is very limited. This study aims to characterize the change in properties as result of environmental factors by examining the effects suffered by epoxy resins containing nano-fillers when exposed to augmented weather conditions. To achieve that goal, neat epoxy resin specimens and epoxy resin samples loaded with 1 percent of carbon nanotubes, silica nanoparticles, nickel or nickelnickel oxide nano-powder were fabricated, and their properties compared. The samples were exposed to three cycles, totaling 246 hours, of UV light and humidity in a QUV accelerated weather chamber and to salt spray in a salt fog chamber. After each exposure cycle, the samples were characterized using optical microscopy, microhardness tests, tensile tests, scanning electron microscopy, and Fourier transform infrared spectroscopy. The specimens electrical conductivity was measured using a four-point probe. The sample analysis after exposure showed changes in the nanocomposite surface structure and microstructure-increase in hardness loss of ultimate tensile strength, in particular for the carbon nanotube composite and dramatic changes in the Youngs modulus among all samples but little change to their sheet resistance. The nanocomposite formulations were also deposited on the surface of 315L stainless steel shim to determine the effects of the augmented weather conditions in the epoxy nanocomposite-metallic pair. Recommendations for future research include examining various composite loadings, developing protocols to achieve better dispersion of fillers on the resin and lengthening exposure times.
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