Optimization of Retting and Extraction Through Constitutive Material Modelling of Plant Stems for Variability Reduction in Extracted Natural Fibers

Natural plant fibers compared to glass fibers can provide a cost effective, lightweight and carbon negative reinforcement for polymer composites. However, the current commercial fiber extraction process induces defects including middle lamellae weakening during retting and kink bands during mechanical working. This leads to high variability in mechanical properties, making these fibers less favorable for structural applications at industrial scale. The aim of current research is to reduce this variability by studying the underlying mechanisms of natural fiber extraction to minimize fiber damage occurring at various steps in the process. In this study, flax stems were retted using the conventional dew/field and lab scale controlled enzymatic retting. The hand decorticated fibers from both methods were compared and enzymatic retting showed promising results in producing fine and uniform fibers as compared to fibers extracted by dew retting. To establish the constitutive parameters of the fibers for Finite Element Modeling (FEM), single retted flax stems were compression tested using a Texture Analyzer. This data can serve as the basis for modeling the mechanical deformation of plant stems passing through breaking rollers which is the first step in extraction after retting. The goal is to optimize the roller design and process conditions required to extract fibers with minimal damage and variability.