Diffuse light transmittance of glass fiber-reinforced polymer laminates for multifunctional load-bearing structures

The diffuse light transmittance of hand lay-up glass fiber-reinforced polymer (GFRP) laminates was investigated. Spectrophotometric experiments were performed on unidirectional and cross-ply glass fiber-reinforced polymer specimens with fiber volume fractions ranging from 0.20 to 0.45. Numerical ray-tracing analysis was used to investigate the experimentally observed wavelength dependency of the diffuse light transmittance. Refractive index mismatches between glass fibers and resin and the presence of air flaws in the laminates were the major parameters increasing light diffusion. Based on the experimental data, analytical models were developed to predict the translucency (haze) of glass fiber-reinforced polymer laminates as a function of the reinforcement weight and total light transmittance. The developed models demonstrate the feasibility of conceiving glass fiber-reinforced polymer skylights with a translucency of 0.90 and a total light transmittance of 0.50 for the daylighting of energy-efficient buildings. It is also shown that laminates with translucencies of lower than 0.30 satisfy minimum total transmittances of 0.83 as required for the encapsulation of photovoltaic cells.