DESIGN OPTIMIZATION OF A LAMINATED COMPOSITE FEMORAL COMPONENT FOR HIP-JOINT ARTHROPLASTY

A multi-level optimization process has been developed specifically to design thick laminated composite structures. The large number of desig n variables present in this type of structure makes such a process a n ecessity so that reasonable computational efficiency can be achieved. At the first level, the in-plane response of a global model is optimiz ed using the stiffnesses of an equivalent orthotropic laminate as the design variables. At the second level, stiffnesses of sublaminates are used to optimize the out-of-plane response while maintaining the in-p lane performance obtained in the first level. Finally, a detailed mode l of a critical local region is developed based on the results from th e second level. This local model is used to optimize the laminate stre ngth using ply orientations as design variables while maintaining the in-plane and out-of-plane performance obtained in the first two levels . The optimization process has been applied to a conceptual model of a composite femoral component for total hip joint replacement. Three-di mensional finite element models are used for the analysis at each of t he three levels. The required computational efficiency is achieved by controlling the complexity of the models, the number of design variabl es, and the nonlinearity of the optimization problem at each level.