Thomas Nowak

Three-dimensional measurement of preform impregnation in composites manufacturing

Abstract An experimental method of flow visualization during impregnation of fibre preforms has been developed. This method extends the visualization technique of making observations through transparent moulds by matching the refractive index of the fibres in the preform with that of the fluid used to simulate the resin system. Wetted portions of the preform then appear transparent while dry portions remain translucent. The desired level of fluid-fibre refractive index match was achieved using a monochromatic illumination source, thereby increasing image contrast between wet and dry regions of the preform and reducing noise within the wetted portion of the image. It has been shown that photometric data analysis can yield three-dimensional information on unsaturated flow from a single image. The technique is illustrated with results of experiments on impregnation of a preform made from unidirectional fabric. These results highlight the importance of local axial spreading of the flow front in radial impregnation of fibre tows with high fibre content.