Effects of the difference between the refractive indices of constituent materials on the light transmittance of glass-particle-dispersed epoxy-matrix optical composites

Abstract

Glass particles with a size d _p of 38–53 μm are incorporated into a clear epoxy matrix and the light transmittance T _L of the composites is measured in the wavelength γ range from 200 to 1100 nm. The net difference ▵_n ^c between the refractive indices of the glass particles and the matrix of the fabricated composite ranged from nearly zero to 0.03. This difference between the refractive indices is achieved by, firstly, selecting the optical properties of dispersed glass particles and secondly, changing the thermal stress in the composite. The effect of the difference ▵_n ^c between the refractive indices of the glass particles and the epoxy matrix on the light transmittance of the composite is obtained. It is found that the light transmission spectrum of the composite is correlated with the relationship between the wavelength dispersion curves of the refractive indices of the glass particles and the matrix. At a fixed wavelength, the T _L−▵_n ^c curve is only dependent on the particle size and volume fraction. The measured T _L−▵_n ^c curves of the composite at a given particle volume fraction and a given particle size show that the maximum light transmittance of the composite appears when ▵_n ^c ≈ 0. The value is about 92% and is nearly the same as that of the pure epoxy matrix.