<p>In a context of growing interest in flax-based composites, this study addresses the lack of data on the behavior of woven flax rovings during the preforming stage of liquid composite molding (LCM) processes. The main objective is to study the fiber volume fraction changes under pressure and to determine the coefficient and exponent in the Toll and Manson relationship. The study implements an experimental methodology that includes compaction tests using a digital microscope to study densification, as well as compression tests using a tensile machine to study deformation, thus clearly distinguishing the two steps involving different mechanics: compaction and compression. Various flax roving samples were studied, and the results revealed significant variability in behavior. This highlights the complexity of the roving structure, which differs significantly from synthetic fiber roving. The experimental data were well-fitted by the Toll model, which successfully reproduced the observed curve. The obtained data are important for validating numerical simulation models of LCM processes. This contributes to optimizing manufacturing and improving the performance of flax-based composites.</p>