A New Image Analysis Assisted Semi-Automatic Geometrical Measurement of Fibers in Thermoplastic Composites: A Case Study on Giant Reed Fibers

Abstract

This work describes a systematic method for the analysis of the attrition and residual morphology of natural fibers during the compounding process by twin-screw extrusion. There are several methods for the assessment of fiber lengths and morphology, although they are usually based on the use of non-affordable apparatus or time-consuming methods. In this research, the variation of morphological features such as the length, diameter and aspect ratio of natural fibers were analyzed by affordable optical scanning methods and open-source software. This article presents the different steps to perform image acquisition, refining and measurement in an automated way, achieving statistically representative results, with thousands of fibers analyzed per scanned sample. The use of this technique for the measurement of giant reed fibers in polyethylene (PE) and polylactide (PLA)-based composite materials has proved that there are no significant differences in the output fiber morphology of the compound, regardless of the fiber feed sizes, extruder scale, or the polymer used as matrix. The ratio of fiber introduced for the production of composites also did not significantly affect the final fiber size. The greatest reduction in size was obtained in the first kneading zone during compounding. Pelletizing or injection molding did not significantly modify the fiber size distribution.