Les matériaux cellulaires fragiles,

Les matériaux cellulaires fragiles, en particulier les mousses céramiques, suscitent aujourd'hui un grand intérêt dans différents domaines d'applications. Ces mousses présentent un bon compromis entre faible densité et performances mécaniques compatible avec une utilisation comme matériaux d'allègement des structures ou d'absorption d'énergie. L'objectif de la présente étude est double. Il consiste, dans un premier temps, à caractériser le comportement mécanique d'une mousse céramique à matrice vitreuse utilisé en tant qu'un absorbeur de choc, dans un second temps, à proposer une modélisation dans le cadre de la mécanique des milieux contenus permettant de prédire la réponse mécanique obtenue sous différents types des sollicitations simples et complexes. Des essais de compression à différentes vitesses de déformations ont été effectués sur des éprouvettes cylindriques pour étudier la sensibilité du matériau vis-à-vis à la vitesse de sollicitation. Les mécanismes d'endommagement mis en jeu lors des essais de compression quasi-statique ont été observés et analysés via la tomographie RX. La réponse multiaxiale a été caractérisée à travers des essais triaxiaux sur la machine Astrée du LMT-Cachan. La surface de charge obtenue grâce à ces essais a été modélisée par le modèle de Deshpande Fleck en faisant varier le coefficient de poisson plastique. Les paramètres du modèle du comportement ont été identifiés sur la base des essais triaxiaux et ont été validés sur des essais d'écrasement des minus – capots métallique remplie de la mousse céramique.

Résultats (Anglais) 1:

Fragile cellular materials, in particular ceramic foams, today raise great interest in various areas of applications. These foams are a good compromise between low density and mechanical performance compatible with use as relief structures or energy absorption materials. The objective of this study is twofold. It involves, as a first step, to characterize the mechanical behaviour of a foam ceramic glass matrix used as a shock absorber, secondly, to propose a modelling in the context of the mechanics contained to predict the mechanical response under different types of simple and complex stresses. Compression at different rates of deformation tests were conducted on cylindrical specimens to investigate the sensitivity of the counterparts at the speed of solicitation material. Mechanisms of damage put at stake during quasi-static compression tests have been observed and analyzed via Positron tomography RX. The multiaxial response has been characterized through Triaxial tests on the Astrée of LMT-Cachan machine. The surface of load obtained through these trials was modelled by Deshpande Fleck model by varying the coefficient of plastic fish. The parameters of the model of behavior have been identified on the basis of Triaxial tests and have been validated on the UNMIS crash tests - ceramic foam-filled metal hoods.

Résultats (Anglais) 2:

Fragile cellular materials, particularly ceramic foams, now of great interest in various fields of applications. These foams have a good compromise between low density and mechanical performance consistent with use as relief structures or energy absorbing materials. The objective of this study is twofold. It consists, in a first time, to characterize the mechanical behavior of a ceramic foam glass matrix used as a shock absorber, in a second time, to provide a modeling part of the mechanics of content media for to predict the mechanical response obtained in different types of simple and complex loads. Compression tests at various strain rates were performed on cylindrical samples to study the sensitivity vis-à-vis the strain rate material. The damage mechanisms involved during quasi-static compression tests were observed and analyzed via RX tomography. The multiaxial response was characterized through triaxial tests on Astraea machine LMT-Cachan. The load surface obtained using these tests was modeled by the model Deshpande Fleck varying the plastic fish coefficient. Behavior of the model parameters were identified on the basis of triaxial tests and have been validated on crash test minus - metal covers filled with ceramic foam.

Résultats (Anglais) 3:

The cellular materials fragile, in particular the foams ceramics, arouse a lot of interest today in various areas of applications. These foams are a good compromise between low density and mechanical performance compatible with use as a materials of alleviation of structures or absorption of energy. The objective of this study is twofold.It is, in a first time, to characterize the mechanical behavior of a ceramic foam to vitreous matrix used as a shock absorber, in a second time, to propose a modeling in the context of the mechanics of content circles for predicting the mechanical response obtained under different types of stress simple and complex.The tests of compression at different speeds of deformations have been carried out on cylindrical test pieces to study the sensitivity of the material opposite to the speed of solicitation. The mechanisms of damage put into play during the tests of compression quasi-static have been observed and analyzed via the X-ray tomographyThe answer robot has been characterized through of triaxial testing on the machine Astree of the LMT-Cachan. The load surface obtained by these tests has been modeled by the model of Deshpande Fleck by varying the coefficient of plastic fish.The parameters of the model of the behavior have been identified on the basis of triaxial testing and have been validated on tests of crushing of UNMIS - metal hoods filled the ceramic foam.