||The use of smart, morphing structures aims to increase aerodynamic efficiency, decreasing fuel consumption and aircraft overall weight. Within this context, piezoelectric materials are of great interest in the design of smart structures due to the reversibility of the piezoelectric effect, allowing them to work both as a sensor and as an actuator. The present work focuses on the development of a geometrically nonlinear finite element formulation for composite beams with embedded piezoelectric layers for application in morphing aerostructures. The proposed formulation is based on Timoshenko's beam theory, taking into account Green type geometric nonlinearities and the beam layerwise mechanical behavior. The set of nonlinear equilibrium equations is solved by means of an iterative-incremental arc length method, and the model is validated by comparing the numerical predictions obtained using the proposed finite element formulation with results available in the open literature. Case studies are also analyzed to verify the performance and sensitivity of the element to design variables such as mechanical and piezoelectric properties, stacking sequence and number of actuators. The good agreement with literature results establishes the code implemented as a versatile tool to analyze smart active-passive composite beams.