Multifunctionnal Cellular Materials
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1188-LL06-06
Multifunctionnal Cellular Materials Michel de Gliniasty1 and Régis Bouchet2 ONERA, BP 72, 29 avenue de la division Leclerc FR-92322 Chatillon Cedex E-mail : [email protected] 2 ETOP International 1
ABSTRACT In many industrial fields, structural materials play a key role in the increase of performance, but new requirements in terms of energy saving, safety, materials economy… lead to more stringent requirements on materials properties. The two usual strategies –microstructure optimisation and shape optimisation-, which act at two different scales, the micrometer scale and above the centimetre scale, become less and less efficient with this new strong demand for multi-functional properties. The largely unexplored millimetre scale, domain of the so called “structural materials”, is a possible answer. Structural materials benefit of an extra degree of freedom well suited for multi-functionality: they allow using combination of materials from different classes, allow geometrical optimisation, and can be naturally integrated in structures such as sandwiches and various stiffened plate geometries. The price to pay for this extra-richness is the extraordinary wide variety of potential solutions to investigate for a given problem. Hence modelling plays a crucial role for selecting and optimising such innovative materials. This paper is an overview of a project, named MAPO (“Materiaux Poreux”), aiming at designing high-temperature materials with acoustical and structural properties.
INTRODUCTION
MAPO is a common project between ONERA, the French aerospace lab, and CNRS the French national centre for research. The objective of this project, launched in 2003 and of 5 years duration, was to explore the “materials by design” approach. Most of the work has been carried out through PhD thesis [1]. The concept of designing a special material for a specific application is not original. At the microstructure scale, the excellent paper by S. Naka and T. Khan [2] is a key contribution in the domain and at the mesostructure scale composite materials are very good examples. In both cases designing a new material was imposed by the required multi-functionality. In the first example high creep tensile strength and good ductility were the –usually contradictory- required properties and the authors attempted to create a γ−γ’ type microstructure in several new alloy systems. Their attempt was not successful as our knowledge of the relationship between microstructure and macroscopic properties is far from being satisfactory for that purpose. In the second example the resulting materials were efficient enough to lead to applications, showing that intermediate scale parameters are easier to handle.
Within the MAPO project it was decided to undertake work on “structured” materials, which means that the degree of freedom would be given by the geometry at a millimetre scale. This is by no means new, but it is usually applied at scales above centimetres.
MATERIALS REQUIREMENTS AND CHOICE
Since ONERA is an aerospace lab, the chos
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