High-speed polarization imaging for failure detection in fiber spinning

Current trends in polymer fiber production for nonwoven material applications focus on increasing production rates and decreasing the fiber thicknesses. The quality of the polymer fibers during the fiber spinning process is influenced by the processing parameters, such as the spinning speed, throughput, and the polymer material. Irregularities in the crystallization process during the extrusion of the fibers can lead to stress concentrations and defects in the fibers that could cause failure of fibers and potential failure of the nonwoven material that is manufactured from those fibers. The ability to recognize these irregularities in fibers using a non-destructive measurement method would reduce the downtimes for production lines as well as provide in-situ quantitative data that could be used for optimization of the production process parameters. In this study, we implemented a high-speed polarization imaging technique that is capable of non-destructive measurement of the internal stress fields as well as detection of defects within a post-fabricated fiber. This imaging technique has been combined with a motion tracking algorithm for accurate alignment of the images corresponding to the same segments of the fiber. The results show that the technique is capable of detecting stress concentration regions in fabricated fibers in static and dynamic testing conditions. The sensitivity of the system also allows to track the changes in the distribution of the internal stress fields in static and dynamic loading. Future studies will apply the technique to the fiber spinning process.