ABSTRACT
This chapter focuses on tissues of collagen fibers which endow their mechanical and transport properties with a directional dependence. It also focuses on directional averaging over fibers. Indeed, while the collagen fibers in the middle zone of articular cartilages may be considered to develop in a three-dimensional isotropic network, they tend to be aligned tangentially to the synovial joint in the upper zone and orthogonally to the subchondral bone in the lower zone. Fibers aligned with a tensile load are certainly in extension, slightly inclined fibers may uncrimp later as the load intensity increases while fibers along orthogonal directions are likely to undergo contraction and to be mechanically inactive. Indeed, at any point of a material, or biological tissue, the thermal, hydraulic and elastic properties may depend on the space direction.
