Optical characterization of nanosilica-filled bisphenol-F epoxy and carbon fiber composites

In this investigation, we examined the effect of curing agents and carbon fiber on the color of epoxy-based composites with varying percentages of nanosilica (NS) as filler. Composites with different concentrations of NS were prepared using a derivative of bisphenol F (bisF) epoxy, cured with diethyl-toluene-diamine (DETDA) or 4,4’- Diaminodiphenylsulfone (DDS), along with carbon fiber composites with bisF and DETDA. The variations of color across samples were correlated to the reflectance in the UV-Vis regimes. We found that curing of samples by DETDA, rather than DDS, leads to higher reflectance in the UV-Vis regimes and almost no effect in the NIR regime. Increments in reflectance within the visible regime are proportional to the NS concentration, whereas such proportionality is not observed in the NIR regime. Reflectance up to 45% is observed initially on addition of 15 wt% NS in both epoxies in NIR spectrum, but further NS addition does not increase reflectance. While the addition of carbon fibers increases mechanical properties, we found their addition makes the composites vulnerable to photodegradation. While the addition of carbon fibers increases mechanical properties, we found their addition makes the composites vulnerable to photodegradation.