The effects of particle pollution on the mechanical behaviour of multilayered systems

The mechanical stability of multilayered structures depends on the intrinsic properties of its layers, as on the external applied solicitations (thermal and/or mechanical). Moreover, the structural imperfections, as the ones generated during the deposition process of the layers, may also play an important role in the mechanical stability of the multilayers. For example, a continuous or a sequential laser irradiation on a multilayered mirror, can produce mechanical damage, which is nucleated at the imperfections of the multilayer. With the aim to study the mechanical damage associated to the imperfections of a multilayered structure, the response to an external stress on multilayered samples, with and without imperfections was analysed. The imperfections were obtained by the dispersion of fine diamond particles on polished substrates, before the deposition of the layers. The mechanically damage was progressively induced by pulling the samples in tension in a SEM. The critical parameters, characterising the behaviour and describing the damage are compared and discussed.