Design optimization of hip prosthesis of thick laminated composites by developing finite element method and sensitivity analysis

An investigation has been performed to develop a finite element method for the analysis of the behavior of complicated three-dimensional thick laminated composite structure, and the method has been applied to the design of hip prosthesis with nonuniform cross-sections. The developed method can accomodate the varying material properties layered within the element and allow the ply-drop-off along the element edges. The numerical results are compared with the analytical solution, and the results;show that the number of elements can be reduced up to 80% within 5% error bounds by using the ply-drop-off element. A method of design sensitivity analysis has also been developed to find the optimal ply angles minimizing the deflection of thick laminated composite structures. The developed finited element method together with the design sensitivity analysis has been applied to design of hip stem, and a procedure for calculating the optimum ply angle is proposed to minimize the rotational micromotion which is one of causes of patients' pain.