Experimental study of lag-twist coupling concept for rotor blade application

A novel passive twist morphing concept is examined for helicopter blades. The concept is demonstrated using a thin-walled rectangular composite beam created with symmetric layup to obtain bend-twist property. The twist of a rotor blade is proposed to be actuated though a movable mass at the blade tip which is able to provide a range of lagwise bending moment during rotation as a result of the centrifugal force. First a set of static bending test is performed which provides detailed characterisation of the deformation and strain distribution of the composite beam subjected to a number of bending loads. The results of the experiment fully verify numerical predictions including finite element approach (FE) and beam cross sectional analysis. A series of simulations are then conducted using the verified numerical model to demonstrate how the desired twist can be effectively achieved by manipulating the size and location of the mass.