Three-Dimensional Strains on Twisted and Swept Composite Rotor Blades in Vacuum
Cheng Chi, Anubhav Datta, Inderjit Chopra, Renliang Chen
Abstract
This paper presents an investigation of the effects of tip sweep on highly twisted composite rotor blades by acquiring strain data in vacuum. Three parametric test cases were designed for strain measurements, and predictions from a special three-dimensional (3-D) finite element method were used for assessment of data. A set of rotating aluminum beams was also tested as a rudimentary baseline. Three sets of composite rotors (straight, twisted, and twisted–swept) were fabricated and tested, and blade properties carefully characterized. Prediction of 3-D strains was conducted using X3D, a 3-D multibody structural dynamic solver for rotor aeroelasticity. Comparison with measured strains showed overall satisfactory agreements. Under centrifugal loading, strong 3-D strain patterns were observed near the twisted–swept tip. The largest increase in strain magnitude is found to be caused by the twist. Evidence of strong lead-lag bending concentrations due to counteracting axial extension and localized in-plane shear were found in the twisted–swept tip.