K. Y. Maalawi’s scientific contributions

The design of thin-walled composite blades is optimized in order to provide high dynamic performance. The optimal design is originated with respect to maximum natural frequency criterion. The optimization model employs the concept of spanwise material grading along the blade axis. Spanwise material grading is achieved by changing the distribution of fiber volume fraction along the blade length. The main blade spar is represented by a beam composed of multiple uniform segments each of which has different cross-sectional properties and length. Transfer matrix technique is used to study the dynamic behavior of such a beam. Design variables are chosen to be the cross-section dimensions, length, fiber orientation angle and fiber volume fraction of each segment. The optimization problem is formulated analytically as non-linear constrained problem solved by sequential quadratic programming technique. Finite element modeling using NX Nastran solver is performed in order to validate the analytical results. The results show that the approach used in this study enhances the dynamic characteristics of the optimized blades as compared with a baseline design.