A finite element approach to the mechanical behavior of 3D interlock fabrics at the scale of constitutive fibers is proposed in this paper. This approach, based on an implicit solution scheme, within a quasi-static framework, considers samples of 3D interlock fabrics as assemblies of fibers and focuses on the detection and modeling of contact-friction interactions between elementary fibers. The unknown initial configuration of interlock fabrics is first determined, starting from an arbitrary configuration, and progressively fulfilling the stacking order between yarns corresponding to the weaving pattern. Various loading tests, and especially transverse compression tests, can then be simulated to characterize the mechanical properties of such fabrics.