Hiring Institution
École Nationale Supérieure d’Arts et Métiers (ENSAM)

PhD-Awarding Institutions
École Nationale Supérieure d’Arts et Métiers (ENSAM)
The University of Sydney (USYD)

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Option 1

Effect of cell morphology and microstructure on the mechanical behaviour of architectured materials

The development of new additive manufacturing processes has changed the way we consider process/microstructure/properties relationships of materials. Furthermore, architectured structures obtained by additive manufacturing can be specifically designed to be used as structural components under complex fatigue loadings. The light-weighting of these structures, and their capability to dissipate energy are advantageous for the development of a new class of components.
To conceive more efficient and robust structures, it is necessary to further understand the effect of the specific microstructures induced by additive manufacturing in the particular case of architectured materials. Indeed the small dimensions of the structural elements (walls, struts) of the elementary cells of the lattices with respect to the microstructure induce some specific local anisotropy that may govern the overall behaviour of the lattice under cyclic loadings. The aim of this project is to establish the link between the process, the microstructures and the mechanical behaviour. There is a current lack of detailed understanding of the underlying damage mechanisms of architectured materials under cyclic loadings and their dependence to process parameters.
A methodology will be developed to (1) understand the microstructures of architectured materials obtained by selective laser meting (SLM) technology using different microstructure characterisation techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction(EBSD); (2) to characterize the quasi-static and fatigue behavior of lattices structures produce by metallic additive manufacturing architectured (3) to identify the damage mechanisms at the local scale and the link with the microstructure by performing in-situ micro-computed tomography loading of the structures. The final step of this study will be to include these aspects into a modeling framework for fatigue prediction of lattices structures.

Option 2

Effect of multiaxial loadings on the mechanical behaviour of architectured materials

The development of new additive manufacturing processes has changed the way we consider process/microstructure/properties relationships of materials. Furthermore, architectured structures obtained by additive manufacturing can be specifically designed to be used as structural components under complex fatigue loadings. The light-weighting of these structures, and their capability to dissipate energy are advantageous for the development of a new class of components.
To conceive more efficient and robust structures, it is necessary to further understand the effect of the cell morphology on the cyclic behavior and in particular in the case of multiaxial loadings. Indeed the complex geometries of the elementary cells of the lattices induce some competitions between microstructures and local stress states that are rarely encounter in standard structures. The aim of this project is to propose a global strategy for the fatigue life prediction of architectured materials including multiaxiality and non local effects.
A methodology will be developed to (1) develop some specific geometries for multiaxial tests on lattices structures ; (2) to process the design structures and evaluate the impact of the process on the multiscale geometrical characterisation of the lattices by the mean of microtomography and in-situ loading, (3) to characterize the mulataxial fatigue behavior of specific cell geometries and (4) to propose an adequate modeling framework for these structures under complex loadings.

Option 3

Development of new post-treatment routes to improve the mechanical behaviour of architectured materials

The development of new additive manufacturing processes has changed the way we consider process/microstructure/properties relationships of materials. Furthermore, architectured structures obtained by additive manufacturing can be specifically designed to be used as structural components under complex fatigue loadings. The light-weighting of these structures, and their capability to dissipate energy are advantageous for the development of a new class of components.
To conceive more efficient and robust structures, it is necessary to further understand the effect of the specific microstructures induced by additive manufacturing in the particular case of architectured materials. Indeed the small dimensions of the structural elements (walls, struts) of the elementary cells of the lattices with respect to the microstructure induce some specific local anisotropy that may govern the overall behaviour of the lattice under cyclic loadings. The aim of this project is to optimize the microstructures obtained by additive manufacturing with respect to the mechanical behavior (static, cyclic) of thin walled structures by optimising the post-treatment of additively manufactured metallic alloys. There is a current lack of detailed understanding of the role of microstructural length scales on the mechanical behavior of architectured materials under cyclic loadings and their dependence to post processing parameters.
A methodology will be developed to (1) understand the microstructures of architectured materials obtained selective laser meting (SLM) technology using different microstructure characterisation techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction(EBSD); (2) to develop specific post treatments such as hot isostatic pressing, heat treatment or case hardening treatments and characterize the obtained microstructures and their on cell morphologies using micro-computed tomography and (3) to evaluate the effect of the post-treatments on the static and fatigue mechanical behavior of the architectured structures.

Nicolas Saintier
Gwenaelle Proust

Mechanics, Materials