Mechanical properties and tensile behavior of flax roving: A review

Environmental considerations are leading manufacturers to integrate more and more plant-fiber-reinforced composites into their products. However, predicting the behavior, mechanical characteristics and feasibility of parts remains complex. During the liquid composite molding (LCM) process, for example, a fundamental step to ensure the service resistance of the composite part is shaping the dry reinforcement, but it is difficult to accurately predict the final shape and integrity of the reinforcement. Flax is among the most commonly used natural fiber reinforcements. An efficient way to understand the deformation and damage mechanisms of the reinforcement is to conduct a numerical simulation of reinforcement at the mesoscopic scale, i.e. considering the tangle of the yarn and particularly the roving of flax fibers. This requires understanding the mechanical behavior of the roving. The stain energy of fibrous reinforcement is, by nature, driven by the tension strain energy, which exhibits the higher rigidity. It is therefore fundamental to be able to characterize the tensile behavior of the reinforcement and of the constitutive yarns. The aim of this review is thus to determine the type of response to be expected, the test conditions as well as the parameters and sources of influence, from cultivation to reinforcement, to be taken into account, to define the best experimental strategy so as to determine the uniaxial tensile mechanical behavior of a flax roving. This review highlights the different mechanisms that determine the tensile behavior of flax rovings and each semi-product; a focus is made on the parameters that influence this behavior, such as humidity, sizing rate, gauge length, etc.