Interfaces and adhesion

Our work in this group focuses on the experimental characterization, modeling and simulation of interactions between solid bodies. This concerns different types of interactions (contact, friction, adhesion, surface transformations, contact thermal resistance, etc.), different types of materials (metallic, concrete, silica, resins, etc.) and different fields of application (transport, space, aeronautics, energy, etc.). We are particularly interested in understanding the phenomena involved, developing behavior models and their mathematical analysis, and developing original numerical methods adapted to this generally non-regular context.

Permanents Members : Caroline Bauzet (MCF AMU), Amal Bechikh (MCF ECM), Frédéric Lebon (Prof AMU), Aurélien Maurel (MCF AMU)

Characterizing and modeling the behavior of adhesive interfaces

We are interested in problems where solid bodies are joined together by means of an adhesive or by spontaneous bonding (direct bonding). The focus will be on experimental characterization of these assemblies (static, fatigue, shock, aging, etc.), phenomenological or deductive modeling (in connection with work in the “mechanics of heterogeneous media and homogenization” theme) and analysis of the mathematical consistency of models (taking uncertainties into account, for example). Mechanical problems may be coupled to several physics (in connection with the “multiphysics couplings” theme).

The scientific questions addressed are mainly related to the strength and service life of assembled structures, taking into account their environment (fatigue, aging, creep, damage/healing, etc.), but also to the mathematical problems raised by the modeling of the phenomena involved.

Modified Arcan tests for cylindrical specimens with image correlation strain field monitoring

Characterization and modeling of direct bonding assembly behavior

The problem concerns the integration of molecular adhesion bonding for space and terrestrial optical devices. The aim of this work is to describe the multiphysical phenomena of adhesion between two surfaces without the addition of polymeric glue or thick liquid. To achieve this, it is necessary to control the sub-nanometer roughness of these surfaces to create van der Walls or covalent bonds at the interface. Various ways of creating and reinforcing adhesion are being explored, such as annealing, UV treatments or plasmas. Efforts are focused on validating methods for reinforcing the mechanical strength of these interfaces, limiting sensitivity to defects and confidence in measurement, while respecting the limitations of the field, and developing simulation models adapted to this interface. To this end, specific methods have been developed to characterize the mechanical properties of direct bonded assemblies: starting with propagation and/or initiation of fracture methods for different loading directions and for static or dynamic loads, and ending with qualification tests on flight models.

Left -> Slicer image produced by molecular adhesion for the Multi Unit Spectroscopic Explorer (MUSE) in the Very Large Telescope (VLT)

Right -> Arcan tests modified to accommodate cylindrical specimens bonded by direct adhesion. Molecularly bonded cube corner model positioned on its mechanical support. The model is mounted on a CNES pyrotechnic test bench to validate its resistance to the launcher's shock specification. 

Characterization and modeling of friction contact behavior

These are problems where solid bodies, generally metals, are joined by contact. On the experimental side, the focus is on characterizing the materials involved, their microstructural evolution under loading (white or brown phase, in collaboration with external academic partners) and the measurement of friction coefficients. Mechanical problems may be coupled to several different types of physics (in line with the “multiphysics coupling” theme).

The scientific questions addressed are mainly related to the strength and service life of structures in contact, but also to the mathematical problems raised by the modeling of the phenomena involved.

Computational and sotware aspects

Because of their often non-regular nature, these problems require us to develop specific numerical formulations (e.g. adaptive mesh refinement, multigrids, a posteriori error calculation, etc.) which can help us deal with certain numerical problems (e.g. related to the diversity of spatial scales). In terms of software, these developments can be applied to in-house tools, i.e. internal finite element codes, or tools developed by an industrial partner (such as Cast3M or PLEIADES), or even commercial codes (such as Abaqus or COMSOL).     

 Simulation in Comsol®, using the imperfect interface model with evolving damage, of the static and cyclic test on the beam-column structure made by bonding pultruded composite beams.