Replacing stitching and weaving in natural fiber reinforcement manufacturing, part 1: mechanical behavior of unidirectional flax fiber composites

Abstract

ABSTRACTThis paper presents a novel natural fiber reinforcement manufacturing approach, based on a combination of short flax fibers and unidirectional flax yarns inspired by a papermaking process. The short fibers are used as a binder, replacing weaving and stitching used in textile-based reinforcements. The tensile and compressive properties of three different composites, in both longitudinal and transverse directions, were studied in order to highlight the effect of the mat binder. The presence of short fibers in the composite resulted in a slight decrease of about 10% of the longitudinal tensile modulus and strength. However, the transverse tensile properties are almost doubled. A similar trend was obtained in compression loading, where the addition of short fibers decreases the compressive modulus and strength. Particularly, the compressive strength in the yarn direction was more influenced by the presence of short fibers and was reduced by 30% compared to a decrease of 10% in the case of tensile loading. Here again, the transverse modulus was slightly increased, even if no effect was observed on the transverse compressive strength. The presence of the short fibers also shows a significant positive effect on the fracture behavior in tensile loading. The fractured surface is more uniform and presents a reduction of the splitting and crack formation along the unidirectional yarn direction.