Total Light Transmittance of Glass Fiber-Reinforced Polymer Laminates for Multifunctional Load-Bearing Structures
Glass fiber-reinforced polymer (GFRP) materials are increasingly used in building construction for the design of multifunctional structures. These composite materials allow the integration of structural functions, building physics functions (mainly thermal insulation) and architectural functions (complex forms and color) in single large-scale building components. GFRP materials also allow the fabrication of translucent structural components with high degree of transparency when optically aligned resins and glass fibers are used, i.e. their refractive indices are identical. In this study the total light transmittance of hand lay-up GFRP laminates for building construction was investigated with a view to two architectural applications: translucent load-bearing structures and the encapsulation of photovoltaic (PV) cells into GFRP building skins of sandwich structures. Spectrophotometric experiments using an integrating sphere set-up were performed on unidirectional and cross-ply GFRP specimens in the range from 20% to 35% fiber volume fraction. Results were compared with the shortcircuit currents generated by amorphous silicon (a-Si) PV cells encapsulated in GFRP laminates exposed to artificial sunlight radiation. The total amount of fibers in the laminates was the major parameter influencing light transmittance, with fiber architecture having little effect. 83% of solar irradiance in the band of 300-800 nm reached the surface of a-Si PV cells encapsulated below structural GFRP laminates with a fiber reinforcement weight of 820 g/m2, demonstrating the feasibility of conceiving multifunctional GFRP structures.