Transparent glass-fiber-reinforced epoxy composites and their optical characteristics

Cured thermosetting epoxy (EP) resins and glass-fiber-reinforced polymer (GFRP) composite materials were prepared to identify the differences in optical properties based on the type of amine curing agent used. The optical properties of the cured product of EP/amine curing agent mixture and transparent GFRP were analyzed using a lens refractometer and UV–Visible spectrophotometer. Among the amine curing agents, the aliphatic amine curing agent PPG-400 has the closest refractive index (RI) to that of glass fiber as well as the highest transmittance. The slight difference in RI between the glass fiber and EP/PPG-400 potentially reduces the phase delay, resulting in high transmittance. The above results imply that transparent, high-transmittance GFRP can be prepared by efficient mixing of the amine curing agent.