In-operando dynamic visualization of flow through porous preforms based on X-ray phase contrast imaging

Direct visualization is often sought to elucidate flow patterns and validate models to predict the filling kinetics during processes whereby a liquid resin infiltrates a textile porous preform. Here, X-ray phase contrast interferometry is evaluated to image in-operando constant flow rate impregnation experiments of a model fluid into glass, carbon and flax fabrics and a 3D printed structure. A methodology is presented to build the dynamic saturation curve based on image analysis of the dark field images, in which the pixel intensity values are transformed into saturation level versus position and time. The results prove the suitability of this technique to observe the progressive saturation averaged through the thickness of translucent and non-translucent preforms. The porosity network formed by the layers of fabric, the refractive properties of the material, the fabric geometry and its position relative to the X-ray setup are reported to be the main parameters affecting image contrast.