Strength Analysis of Composite Turbine Blades

Abstract

Turbine engine blades can be made in a laminate form of composite layers oriented in various directions. In this work we derive two approximate analytical models to describe the stress/strain field within each layer of a rotating turbine blade. At the foundation of the model is the fundamental observation that the very low width-to-thickness ratio precludes the use of the assumptions of classical lamination theory. Reasonable assumptions regarding the response distributions that are consistent with overall equilibrium lead to the appropriate analytical expressions. Strength predictions are made for three different blade architectures. one with orientations used by an existing design. the second prone to failure. and the third not prone to failure for a given angular velocity. The results show that an optimum blade architecture can be determined using these models. A comparison is made between the predicted results by an existing model and one of the present models by using effective material properties of the laminate. A computer code for IBM-PC computer has been written using these models for conducting the strength analysis of the turbine blade.