In the field of aeronautics (Aircraft, helicopters, space launchers...), as in the field of the automobile, reducing the harmful effects of acoustics constitutes a major concern at the international level and justifies the call for further research. With these challenges in mind, the manufacturers have expressed the need for simple models immediately available as early as the stage of preliminary drafts. This Master's Thesis presents the study and the validation of three different approaches to meet this industrial need. The first approach is based on the propagation of waves in the structure; the second approach uses the technique of SEA by calculating the equivalent damping; and the last approach uses the modal technique.In the three approaches, the transfer matrix method has been used to study the succession of layers. Applying these approaches to some aircraft structures confirm their relevance in relation to more exact and costly methods, such as the finite elements method.

The research on tribology and wear of the metals and composites has always been the topic of interest to understand the behavior and life of them. The wear of the materials with three-body contact has been of particular interest because the wear debris generated due to the wear and tear between the contact surfaces in constant motion will aggravate the wear rate of the contact surfaces. Hence it would be interesting to understand the stress distribution inside the materials with three-body contact. The current research presents the stress distribution within the materials which are in three-body contact modeling them as plain-strain problems with three different models viz., point force model, uniform pressure model and Hertzian Pressure model. The stress distribution of all the three cases are numerically computed and compared and the stress intensity factor is calculated in each case.