Measuring spatial fiber orientation—A method for quality control of fiber reinforced plastics

Properties of short and especially long fiber reinforced thermoplastics highly depend on fiber length distribution in the processed material and local fiber orientation in the processed part. Good mechanical performance is achieved, if overall mean fiber length is high and fiber orientation is well adapted to the external stress situation. If non optimized processing parameters are applied, a decay in mean fiber length and unfavorably orientated fibers in areas of high stress may result. Knowledge of morphological parameters provides quantitative information about the injection molding process and the design of the cavity. Recent advances in automated methods of measuring fiber length and spatial fiber orientation, which are based on image processing systems, reveal even small differences in morphology. Measuring spatial fiber orientation on polished cross‐sections by means of an image processor is a newer concept, that allows fast and quantitative description and optimization of the mold filling process. Some examples show the performance of the method; the measured fiber orientation is used to model thermal expansion and Young's modulus.