Transmission of ultraviolet light through reinforcement fabrics and its effect on ultraviolet curing of composite laminates

The ultraviolet transmission of various reinforcement textiles was quantified experimentally for the case of incidence of light normal on the fabric plane, and correlated with the curing behavior of laminates incorporating these fabrics. For glass fiber fabrics wetted with polyester resin, light is transmitted through the voids between the fiber bundles and through the fiber bundles. Multiscale modeling of the fabric geometry allows the local transmission to be estimated and the average total transmission to be quantified. The results of curing experiments suggest that the degree of through-cure achieved after a given cure time is correlated to the fabric transmission. Both are determined by the laminate thickness, the fabric architecture and the fiber volume fraction, i.e., the fiber packing density. While the transmission is reduced by the presence of the reinforcement fabrics, the total resin volume is reduced when compared with that of a resin only sample of the same thickness. A lower radiation dose is sufficient for curing, which partially compensates for the effect of reduced transmission.