NASA experiments have indicated the need for non-linear damping models to describe the motion of large flexible space structures. In this work, energy type non-linear damping models in an infinite dimensional setting are studied. According to the geometry of the structures considered, energy type non-linear damping models are divided into two types. Their frequency response is found and compared with that given by linear models and non-linear stiffness models. It is concluded that non-linear damping models do not produce peculiar behaviours such as internal resonance, jump phenomenon or chaotic behaviour.