Responsible : Ali ZAOUI
The research of this team deals with the development and use of modeling at several scales with the aim of improving the understanding of the behavior of geomaterials and infrastructures by taking into account the multi-scale nature of the problems encountered. It is a question of modeling the behavior and of characterizing materials by going from the nanoscale to the macroscopic scale
Three main topics are considered in this team: topic 1 focuses exclusively on studies at the nanoscale (modeling at small scales), topic 2 is based on the different scales ranging from nano to macro and finally the topic 3 focuses on modeling at the macroscopic scale.
The subjects considered are mainly devoted to geomaterials at all scales up to that of the infrastructure, the various couplings (hydro-thermo-mechanical, physico-chemical ...) and the interaction of the structure with its environment.
On the other hand, the characterization of the various materials (including geomaterials) constitutes the main subject of topic 2 where we can note, in particular, experimental work based on instrumented indentation as well as its development.
The works are classified into three topics:
This topic aims to study the properties of geomaterials at the nanoscale in variable environments of temperature, pressure, fluid and contaminants both in volume and on surface. We use in particular atomistic modeling and simulation methods including first-principles methods (ab initio), molecular dynamics and Monte Carlo. The corresponding works cover a wide range of systems including rocks, clays and concrete. The originality lies in the pioneering role of LGCgE in this area. It makes it possible to position it at the best levels on the international level with both fundamental and applied aspects.
This topic benefits from close international collaborations with colleagues from Sweden, the United States, Austria, China and England. An international master course on nanoscience and nanotechnology in civil engineering has been created. It opens the door to new PhD students to be specialized in this field.
This topic is interested in all types of materials: massive homogeneous or heterogeneous materials, metallic, ceramic or polymers, coated or not. The main objective is the determination of their mechanical properties on local and global scales and the identification of their behavior laws in small and large deformations according to their properties. This theme is addressed with an emphasis on the relationship between modeling and experimentation. This is why, a first axis concerns the use of instrumented indentation for the mechanical characterization of materials. This approach makes it possible to consider a wide variety of properties and therefore to be interested in purely elastoplastic materials, such as metals and ceramics, or in polymeric materials for which the viscous aspect can be taken into account. With regard to polymer systems, an emphasis is under development and experimental verification of behavioral models and criteria of fatigue and rupture.
Mechanical characterization by multiscale indentation
Mechanical characterization by multiscale indentation
In general, we are interested in the mechanical characterization of materials, mainly by indentation, with a materials approach taking into account various parameters (multiphasic, heterogeneous, porous, coated ...) and an approach rather oriented towards the development of the technique of indentation. All measurement scales are covered, from nano to macro, different modes are used (classic, CSM and multi-cyclic) and different properties are studied.
In addition to the mechanical characterization of materials, we are interested in the development of instrumented indentation at different measurement scales for the determination of mechanical surface properties. It is mainly a question of hardness but also of the modulus of elasticity, the toughness and the mechanical properties of traction by inverse methods, the laws of behavior in creep and in relaxation. Our goal is to deepen our knowledge of the methodology, its contours and its limits for obtaining reliable and relevant properties. This is why we are studying a wide variety of materials in massive forms with different mechanical behaviors (from metals to ceramics), highly heterogeneous materials such as geomaterials (concretes), materials coated with thin films (<10 μm) or thicker (some 100 μm), homogeneous or heterogeneous structures or materials with a gradient of surface properties obtained by mechanical or thermochemical treatments. This diversity of case studies has allowed us to make good progress on the knowledge of new materials. However, there are still scientific barrier to be overcome, such as the taking into account of experimental parameters (rigidity of the machine, tip defect ...), the effect of size in indentation, the modeling of the mechanical properties of coated or gradient materials and finally the search for relevant parameters to characterize highly heterogeneous materials such as those of civil engineering.
The problematic dealt with in this theme concerns the modeling and forecasting of the behavior of complex structures by taking into account different couplings (mechanical, thermal, hydraulic, soil-atmosphere, soil-structure), complex loads, such as seismic loading or movement of soil linked to excavations or deformations of thermal or water origin and complex geometries (3D, evolutionary or fractured environments ...).
Originality and positioning
The originality of the work lies in the use of a global numerical approach integrating the different elements of complexity (3D geometry, non-linear behavior, different coupling of phenomena ...) to analyze the behavior of structures with different types of stresses, including the stresses imposed by the environment of the structure. Integrated modeling often leads to simpler models and/or practical recommendations for the design, rehabilitation and or operation of the structure.
Approach and actions undertaken
The approach is based on new digital developments, the integration of part of these developments in existing software or platforms, the validation of models on tests or observations and their applications to the analysis of the behavior of works under different types of stress.
