Triphasic Orthotropic Laminate odel for Cartilage Curling Behavior: ixed Charge Density Versus echanical Properties Inhomogeneity

smotic pressure and associated residual stresses play important oles in cartilage development and biomechanical function. The urling behavior of articular cartilage was believed to be the ombination of results from the osmotic pressure derived from xed negative charges on proteoglycans and the structural and ompositional and material property inhomogeneities within the issue. In the present study, the in vitro swelling and curling beaviors of thin strips of cartilage were analyzed with a new strucural model using the triphasic mixture theory with a collagenroteoglycan solid matrix composed of a three-layered laminate ith each layer possessing a distinct set of orthotropic properties. conewise linear elastic matrix was also incorporated to account or the well-known tension-compression nonlinearity of the tissue. his model can account, for the first time, for the swelling-induced urvatures found in published experimental results on excised carilage samples. The results suggest that for a charged-hydrated oft tissue, such as articular cartilage, the balance of proteoglyan swelling and the collagen restraining within the solid matrix s the origin of the in situ residual stress, and that the layered ollagen ultrastructure, e.g., relatively dense and with high stiffess at the articular surface, play the dominate role in determinng curling behaviors of such tissues. DOI: 10.1115/1.4000942