. . . . . "Lanceurs (astronautique)" . "Th\u00E8ses et \u00E9crits acad\u00E9miques" . . . . . . . . "M\u00E9thode des \u00E9l\u00E9ments finis ondulatoires (WFEM)" . . "\u00C9l\u00E9ments finis, M\u00E9thode des" . . "Approche de SOAR" . "During its mission, a launch vehicle is subject to broadband, severe, aeroacoustic and structure-borne excitations of various provenances, which can endanger the survivability of the payload and the vehicles electronic equipment, and consequently the success of the mission. Aerospace structures are generally characterized by the use of exotic composite materials of various configurations and thicknesses, as well as by their extensively complex geometries and connections between different subsystems. It is therefore of crucial importance for the modern aerospace industry, the development of analytical and numerical tools that can accurately predict the vibroacoustic response of large, composite structures of various geometries and subject to a combination of aeroacoustic excitations. Recently, a lot of research has been conducted on the modelling of wave propagation characteristics within composite structures. In this study, the Wave Finite Element Method (WFEM) is used in order to predict the wave dispersion characteristics within orthotropic composite structures of various geometries, namely flat panels, singly curved panels, doubly curved panels and cylindrical shells. These characteristics are initially used for predicting the modal density and the coupling loss factor of the structures connected to the acoustic medium. Subsequently the broad-band Transmission Loss (TL) of the modelled structures within a Statistical Energy Analysis (SEA) wave-context approach is calculated. Mainly due to the extensive geometric complexity of structures, the use of Finite Element(FE) modelling within the aerospace industry is frequently inevitable. The use of such models is limited mainly because of the large computation time demanded even for calculations in the low frequency range. During the last years, a lot of researchers focus on the model reduction of large FE models, in order to make their application feasible. In this study, the Second Order ARnoldi (SOAR) reduction approach is adopted, in order to minimize the computation time for a fully coupled composite structural-acoustic system, while at the same time retaining a satisfactory accuracy of the prediction in a broadband sense. The system is modelled under various aeroacoustic excitations, namely a diffused acoustic field and a Turbulent Boundary Layer (TBL) excitation. Experimental validation of the developed tools is conducted on a set of orthotropic sandwich composite structures. Initially, the wave propagation characteristics of a flat panel are measured and the experimental results are compared to the WFEM predictions. The later are used in order to formulate an Equivalent Single Layer (ESL) approach for the modelling of the spatial response of the panel within a dynamic stiffness matrix approach. The effect of the temperature of the structure as well as of the acoustic medium on the vibroacoustic response of the system is examined and analyzed. Subsequently, a model of the SYLDA structure, also made of an orthotropic sandwich material, is tested mainly in order to investigate the coupling nature between its various subsystems. The developed ESL modelling is used for an efficient calculation of the response of the structure in the lower frequency range, while for higher frequencies a hybrid WFEM/FEM formulation for modelling discontinuous structures is used." . "2012" . "Ondes -- Propagation" . "Pendant sa mission, un lanceur est soumis \u00E0 des excitations large bande, s\u00E9v\u00E8res, a\u00E9rodynamiques, de provenances diverses, qui peuvent mettre en danger la survivabilit\u00E9 de la charge utile et de l\u2019\u00E9quipement \u00E9lectronique du v\u00E9hicule, et par cons\u00E9quent le succ\u00E8s de la mission. Les structures a\u00E9rospatiales sont g\u00E9n\u00E9ralement caract\u00E9ris\u00E9es par l\u2019utilisation de mat\u00E9riaux composites exotiques des configurations et des \u00E9paisseurs variantes, ainsi que par leurs g\u00E9om\u00E9tries largement complexes. Il est donc d\u2019une importance cruciale pour l\u2019industrie a\u00E9rospatiale moderne, le d\u00E9veloppement d\u2019outils analytiques et num\u00E9riques qui peuvent pr\u00E9dire avec pr\u00E9cision la r\u00E9ponse vibroacoustique des structures larges, composites de diff\u00E9rentes g\u00E9om\u00E9tries et soumis \u00E0 une combinaison des excitations a\u00E9roacoustiques. R\u00E9cemment, un grand nombre de recherches ont \u00E9t\u00E9 men\u00E9es sur la mod\u00E9lisation des caract\u00E9ristiques de propagation des ondes au sein des structures composites. Dans cette \u00E9tude, la m\u00E9thode des \u00E9l\u00E9ments finis ondulatoires (WFEM) est utilis\u00E9e afin de pr\u00E9dire les caract\u00E9ristiques de dispersion des ondes dans des structures composites orthotropes de g\u00E9om\u00E9tries variables, nomm\u00E9ment des plaques plates, des panneaux simplement courb\u00E9s, des panneaux doublement courb\u00E9s et des coques cylindriques. Ces caract\u00E9ristiques sont initialement utilis\u00E9es pour pr\u00E9dire la densit\u00E9 modale et le facteur de perte par couplage des structures connect\u00E9es au milieu acoustique. Par la suite, la perte de transmission (TL) \u00E0 large bande des structures mod\u00E9lis\u00E9es dans le cadre d\u2019une analyse statistique \u00E9nerg\u00E9tique (SEA) dans un contexte ondulatoire est calcul\u00E9e. Principalement en raison de la complexit\u00E9 g\u00E9om\u00E9trique importante de structures, l\u2019utilisation des \u00E9l\u00E9ments finis (FE) au sein de l\u2019industrie a\u00E9rospatiale est souvent in\u00E9vitable. L\u2019utilisation de ces mod\u00E8les est limit\u00E9e principalement \u00E0 cause du temps de calcul exig\u00E9, m\u00EAme pour les calculs dans la bande basses fr\u00E9quences. Au cours des derni\u00E8res ann\u00E9es, beaucoup de chercheurs travaillent sur la r\u00E9duction de mod\u00E8les FE, afin de rendre leur application possible pour des syst\u00E8mes larges. Dans cette \u00E9tude, l\u2019approche de SOAR est adopt\u00E9e, afin de minimiser le temps de calcul pour un syst\u00E8me coupl\u00E9 de type structurel-acoustique, tout en conservant une pr\u00E9cision satisfaisante de la pr\u00E9diction dans un sens large bande. Le syst\u00E8me est mod\u00E9lis\u00E9 sous diverses excitations a\u00E9roacoustiques, nomm\u00E9ment un champ acoustique diffus et une couche limite turbulente (TBL).La validation exp\u00E9rimentale des outils d\u00E9velopp\u00E9s est r\u00E9alis\u00E9e sur un ensemble de structures sandwich composites orthotropes. Ces derniers sont utilis\u00E9s afin de formuler une approche couche \u00E9quivalente unique (ESL) pour la mod\u00E9lisation de la r\u00E9ponse spatiale du panneau dans le contexte d\u2019une approche de matrice de raideur dynamique. L\u2019effet de la temp\u00E9rature de la structure ainsi que du milieu acoustique sur la r\u00E9ponse du syst\u00E8me vibroacoustique est examin\u00E9 et analys\u00E9. Par la suite, un mod\u00E8le de la structure SYLDA, \u00E9galement fait d\u2019un mat\u00E9riau sandwich orthotrope, est test\u00E9 principalement dans le but d\u2019enqu\u00EAter sur la nature de couplage entre ses divers sous-syst\u00E8mes. La mod\u00E9lisation ESL pr\u00E9c\u00E9demment d\u00E9velopp\u00E9e est utilis\u00E9 pour un calcul efficace de la r\u00E9ponse de la structure dans la gamme des basses et moyennes fr\u00E9quences, tandis que pour des fr\u00E9quences plus \u00E9lev\u00E9es, une hybridisation WFEM / FEM pour la mod\u00E9lisation des structures discontinues est utilis\u00E9." . "R\u00E9ponse vibroacoustique" . "Analyse statistique \u00E9nerg\u00E9tique (SEA)" . . "Text" . . "Excitations large bande" . . "Prediction of the vibroacoustic response of aerospace composite structures in a broadband frequency range" . "Prediction of the vibroacoustic response of aerospace composite structures in a broadband frequency range" . . . .