A mathematical model describing the nonlinear vibration of horizontal axis wind turbine
(HAWT) blades is proposed in this paper. The system consists of a rotating blade and four
components of deformation including longitudinal vibration (named axial extension), outof-
plane bend (named flap), in-plane/edgewise bend (named lead/lag) and torsion (named
feather). It is assumed that the center of mass, shear center and aerodynamic center of a
cross section all lie on the chord line, and do not coincide with each other. The structural
damping of the blade, which is brought about by materials and fillers is taken into account
based on the Kelvin–Voigt theory of composite materials approximately. The equivalent
viscosity factor can be determined from empirical data, theoretical computation and experimental
test. Gravitational loading and aerodynamic loading are considered as distributed
forces and moments acting on blade sections. A set of partial differential equations governing
the coupled, nonlinear vibration is established by applying the generalized Hamiltonian
principle, and the current model is verified by previous models. The solution of equations is
discussed, and examples concerning the static deformation, aeroelastic stability and
dynamics of the blade are given.