MECHANICAL BEHAVIOR OF FIBROUS MATERIALS WITH APPLICATION TO CONNECTIVE TISSUE
A review of the generic mechanical behaviour of random networks of filaments subjected to tension and compression is presented in this article. The system is athermal, in the sense that thermal fluctuations prevalent on the nanoscale have no effect on the mechanics of these fibers. The fibers are connected at cross-linking sites and behave as beams with axial, bending and torsional stiffness. Transient contacts between filaments are important primarily in compression. The stress-strain curve has three regimes in both tension and compression. The first regime is linear elastic, with modulus identical in tension and compression. The second regime is defined by exponential stiffening in tension and is associated with the non-affine convection of filaments. In compression, the stress-strain curve softens in the second regime and a plateau appears during which the fibers align in the plane perpendicular to the compression direction. The third regime corresponds to strong stiffening in both tension and compression. The cause of stiffening in tension is the formation of a load-bearing structure of fibers aligned in the tensile direction, while in compression, stiffening is associated with the formation of a large number of contacts between fibers. In both tension and compression, a very large Poisson effect is observed. These results are compared with the behavior of collagenous connective tissue and important similarities are observed. It is concluded that the type of models presented here are adequate for the representation of tissue mechanics.