Elastic tailoring of spinning advanced composite fan blades

A general finite element analysis based procedure is developed for the analysis and design of spinning advanced composite turbo-propellers. Turbo-propeller blades are very thick at root and very thin at tip. So effects of transverse shear deformation are significant at the root while geometrically non-linear behavior is observed at the tip. These effects have been incorporated in the current analysis procedure. Since existing plate/shell finite elements have the inability to model both thick and thin plate/shell structures, a new triangular finite element has been developed for the current analysis. Different order polynomials are used to model transverse deflections and the in-plane displacements and rotations to properly capture the transverse shear strain behavior for thin plates and to avoid the shear-locking effect present in existing finite elements. A first-order transverse shear deformation plate theory is used to model transverse shear deformation, an effect significant in composite structures. Important structural effects that influence the behavior of spinning blades include effect of centrifugal forces on the stiffness behavior, effect of pretwist angle and pretwist axis location on the stiffness and bending, extension and torsion coupling behavior in composites, and, effect of laminate ply orientation on the stiffness behavior. These effects are included in the analysis procedure and are studied to understand the effect of individual parameters.;Results are presented to compare the new element with available triangular finite elements to show the superiority of the element. Comparisons are made between results from the current analysis procedure and data available from static deflection and free vibration tests of spinning flat and plate structures. Effects of parameters like plate pitch, precone, pretwist and laminate layup on the static and free vibration analysis of spinning flat and pretwisted plates are presented. Stability behavior of spinning flat plates is also studied. Finally an actual NASA turbo-propeller blade is modeled using the developed procedure to study the free vibration behavior of the blade. Optimization studies are presented to see the effect of material properties and laminate ply orientation on the static deflection and free vibration behavior of spinning turbo-propeller blades and to optimize this behavior.