The Design of a Continuous Fiber Composite Surface Hip Replacement

The design of a continuous fiber composite surface femoral shell having the same elastic properties as bone is presented. Contact between the femoral ball and acetabular cup was modeled as an elastic spherical ball loaded on an elastic semi-infinite body. The elastic constants of the composite were obtained by using empirically modified and experimentally verified rule-of-mixture equations relating the elastic properties of bone to those of both the fibers and matrix. The stresses were calculated for the contact problem and applied to a cross-ply laminate made up of orthotropic lamina. An interactive tensor failure criterion was used to select a safe design for polyimide, ultra-high molecular weight (U.H.M.W.), high density polyethylene, acrylic bone cement and epoxy composites using either glass or kevlar fibers. The safest composite design appears to be that made with a polyimide or epoxy matrix and glass or kevlar fibers.