A micro constitutive model for ultra-high molecular weight polyethylene orthopaedic implant bearings

Ultra-high molecular weight polyethylene (UHMWPE) is a tough semi-crystalline polymer employed widely as a bearing material in total joint replacements. The micromechanical model has been presented that predicts stiffness of UHMWPE as an aggregate of crystalline inclusions (lamellae) embedded in a rubbery matrix of amorphous polymer chains. The differential scheme was chosen for its ability to represent the interaction between an inclusion and the matrix. Numerical simulations show that increasing lamellar thickness results in less stiffness, less shear stress imposed on the lamellae, indicates that thick lamellae are desirable for UHMWPE materials utilized in total joint replacement bearings.