Method for three-dimensional evaluation and visualization of the distribution of fibres in glass-fibre reinforced injection molded parts by µ-X-ray computed tomography

Glass-fibre reinforced polymer matrix composites exhibit superior properties to traditional materials. Thus, they have found a broad variety of applications in modern industry. For process development and quality control sophisticated three-dimensional methods for non-destructive characterization are needed. X-ray computed tomography (CT) is a powerful radiographic non-destructive-testing method to locate and size volumetric details in three dimensions. This paper comprises the characterization of short glass-fibre reinforced injection molded polymeric parts by µ-CT to measure lengths and in particular the three-dimensional orientation of the fibres. To measure a maximum of sample volume the µ-CT-measurements were performed with resolutions close to the diameter of the fibres. The CT-data were processed by various three-dimensional filters such as anisotropic diffusion, threshold and thinning operations. The anisotropic diffusion filter leads to better contrast between fibres and the polymeric matrix. Therefore, the individual fibres can be extracted by thresholding and the medial axis of every fibre can be determined by a thinning algorithm. From these data fibre lengths and the three-dimensional orientation can be determined. The final result of the CT-evaluation procedure is a three-dimensional representation and visualization of the fibre distribution by means of color coded vector-fields and glyphs. In addition, the experimental CT-results were compared to simulation results of the injection molding process using Moldflow. The differences between the CT-results and the simulation are visualized and analyzed in three dimensions by means of the orientation tensor. The CT-results correspond to the calculated fibre orientation in the injection molded part quite well.