Tuning of Blade Natural Frequencies Outside High Excitation Region by using Ceramic Particle Reinforced Composite Materials for a Typical Gas Turbine Engine Compressor Blade

Composite materials have time and again proven to be highly useful, especially in the aerospace industry with the increasing need for light-weight materials albeit with high stiffness to strength ratios. The Ceramic Particle Reinforced Composites can be effectively utilized in tuning the natural frequencies of components by varying the volume fractions up to 40% with the help of Representative Volume Element (RVE) / Unit Cell Models as explained in Reference [1].

The aim of this paper is to tune the natural frequencies of a typical blade used in a gas turbine engine by modifying the material properties without changing the design profile significantly. The design profiles of blades are arrived at after a lot of engineering iterations from aerodynamics stability point of view and are also finalized based on meeting key performance parameters. However, the structural analysis studies are carried out after the profile generation, which may sometime predict that the natural frequencies are within the high excitation range of the engine. This adds to the risk of failure due to vibrational stresses caused by resonant frequencies where the vibration loads are higher in magnitude. Therefore, if the natural frequencies of the blades can be tuned in such a way that these do not lie within the high excitation frequency range, then it can save engineering costs and avoid rework in the design phase. In addition, it can help in saving the weight without compromising on the structural integrity of the blades. The studies will be performed using the commercial FE software (Ansys Workbench) by homogenizing the effective material properties and this will involve a direct comparison of natural frequencies and mode shapes with the existing metallic v. proposed composite material models.