Résumé
Annulus fibrosus (AF) is the outer tissue of intervertebral disc (IVD) which is a highly specialized element of the spine that provides flexibility and dissipative capacities. When mechanical loads are transmitted along the spine, IVD mainly supports compression and bending stresses. This results in a hydrostatic excessive pressure in the central nucleus pulposus and generates circumferential tensile stresses in the surrounding AF. To hold these large circumferential strains, AF tissue is assimilated to a composite material made of oriented structures of collagen fibers embedded in a highly hydrated (60−70%) matrix [6]. This particular microstructure and biphasic composition confers to AF a non-linear and anisotropic behavior. Many experimental studies have underlined the anisotropic and non-linear mechanical behavior of AF using uniaxial tensile tests [5-7]. However, few authors have experimentally investigated the biaxial behavior [8].