| Two distinct analysis methodologies are presented for composite rotor blades. The first approach formulates a simple, analytical composite beam model in order to predict static and dynamic behavior. In this model, both cross-section and elastica analyses are developed analytically. Results can be obtained either in closed form or in only a few minutes on a personal computer. This approach is needed as a cause-effect relationship between configuration and response must be clearly understood and numerous "preliminary design" iterations may be required. The second theory is formulated for nonhomogeneous, anisotropic elastic beams with initial curvature and shear. The cross-sectional deformations are derived from three-dimensional elasticity by a perturbation procedure which generates a hierarchy of equations. In this methodology, a linear two-dimensional cross-section analysis whose results determine the constitutive law for a nonlinear one-dimensional elastica analysis is presented. A general mixed hybrid finite element variational principle to solve the one-dimensional elastica equations is formulated. This is an amenable approach and practical tool for "detailed design" analysis/optimization. The present work, thus, aims to construct a unified structural technology for both preliminary design and detailed analysis of composite rotor blades. Validation of these approaches through tests on model configurations and comparison with the existing literature are given. |
