Failure Analysis of Small Composite Sandwich Turbine Blade Subjected to Extreme Wind Load

Abstract

In this paper, the progressive failure process of composite sandwich wind turbine blades subjected to wind load is studied via both theoretical and experimental approaches. In the theoretical study, the wind pressure acted on the wind blade surface is estimated in an aerodynamic analysis. The stresses in the wind blade are determined using the finite element code ANSYS in which the skin and the core of the blade are modeled using shell and solid elements, respectively. A phenomenological failure criterion is adopted to predict the first-ply failure strength of the blade. After the occurrence of the initial failure, the material properties at the failure locations are modified following a material degradation rule. The updated stiffness matrix of the blade is then obtained with the consideration of the changes of the material properties and configuration of the blade. An incremental load approach together with a sequential stiffness adjustment technique is used to trace the load-displacement curve and thus determine the ultimate strength of the blade. In the experimental investigation, a composite sandwich wind blade was fabricated for strength testing. In the test, the Whiffle-tree approach was used to simulate the wind load on the blade. The measured ultimate load of the wind blade was then used to validate the accuracy of the proposed method for failure analysis of composite sandwich wind blades.