The inclusion of simple damping of viscous type in the incremental variational equation governing the non-linear motions of multilayer beams is described. Various problems of forced non-linear response of three-layer sandwich beams are studied. Plots of the response curves reveal some complicated and interesting variation of the amplitudes of different harmonic terms, especially in the case of an unsymmetrically layered beam in which a quadratic type of non-linearity is observed. © 1985.