Brilliant defense of a supervisor of the Chair Augmented Soldier

Laurent Mahéo brilliantly defended his Habilitation to Supervise Research on Tuesday, June 18, 2019 at the Écoles de Saint-Cyr Coëtquidan. He presented his thesis entitled “Mechanical behavior of cellular materials” summarizing the research projects he has conducted since 2002.

His research activities fall under the theme of protection of goods and people and are particularly interested in the dynamic behavior of sandwich materials subjected to rapid impact-type stresses.

They concern first of all the dynamic tests. The measurement of the contact force during an impact is often made difficult because of the vibrations generated during the impact. The use of a projectile-sensor with gauges makes it possible to measure the evolution of the effort in the case of an impact on a naval sheet and in the case of the dynamic traction of holding straps for military applications.

They then concern the models used in numerical simulation by finite elements to represent time and space and thus describe transient dynamics. Spurious oscillations from rapid loading coupled with the inadequacy of models to represent these loads can be reduced with several tools such as damping time advance schemes or artificial viscosity. A study on the failure of composites using the discrete element method is also detailed and shows the ability of the method to describe the cracking phenomena.

Finally, they concern the mechanical behavior of sandwich materials by studying specifically the dynamic behavior of the sandwich complex and its constituents, the “skin” material and the “core” material. An in-depth study is then proposed for cellular materials. The first step is to examine the effects of the microstructure on the macroscopic scale behavior. An investigation on hyperelastic potentials is carried out in order to propose a model capable of describing the specificities of these materials: large transformations, strong compressibility… To feed the reflection of this modeling, multiaxial tests have been imagined, developed and realized. Finally, an application for the use of foams with thermo-mechanical properties is presented.

The jury was composed of :
– Pr Nadia BAHLOULI (rapporteur), Univ Strasbourg
– Pr Philippe LORONG (rapporteur), Arts et Métiers Paris
– Pr Eric MARKIEWICZ (rapporteur), Univ polytechnique des Hauts de Fance, Valenciennes
– Pr Philippe VIOT, Arts et Métiers Bordeaux
– Pr Vincent GROLLEAU, ETH Zurich
– Pr Gérard RIO, UBS Lorient

Laurent Mahéo is co-supervisor of the thesis that Morwan Adlafi is conducting within the Chair Augmented Soldier in the Digital Battlespace, which has as its theme “the dynamic behavior of metallic materials obtained by additive manufacturing (3D printing).