Objectives

Fort existing studies, the goal of our team for the next four years is to continue the research activities under way by continuing to develop strategies for analysis and modeling of assemblies based on various collaborations (ie, industrial , national and international university). The various research themes proposed by this group have strong applications in the field of marine renewable energy.

Science projects planned for the group "Mechanics of Assemblies" are presented as follows:

Modeling the behavior of bonded composite joints

(Participants: Jean-Yves Cognard, Romain Créac'hcadec, Malick Diakaté, Bernard and Laurent Sohier Gineste)

An important research topic in the context of structural optimization for industrial innovation is associated with the use of composite joints (metallic materials - composite materials). The design of such assemblies requires the establishment of procedures for specific tests in order to search geometries assemblies limiting stresses (especially for composites) and to control the influence of environment on sustainability in service. These points are particularly important for marine applications (ships, offshore structures, applications in the field of marine renewable energy). Replacing traditional methods of assembly by bonding offers significant benefits, including relief, reduction of galvanic corrosion problems and the potential for reducing manufacturing costs. Thus, the bonding must be integrated into the design stage, which requires the availability of tools that are adapted to the marine industry and have been validated by tests on representative structures, particularly for marine applications. In addition, the new REACH regulation limit, in particular, the use of surface preparations techniques developed to increase the durability of bonded assemblies.

Durability of adhesive joint industrial marine environment.

Two topics of study are proposed to analyze the influence of couplings between aging and thermomechanical loading:

1. 3D modeling service behavior of a bonded assembly under thermomechanical loads. The approaches currently used to consider possible experimental study of the behavior of a bonded assembly under cyclic loading and under loadings creep and relaxation as a function of temperature. Furthermore, the use of the traction machine twist available LBMS will allow to analyze the influence of non-proportional multiaxial loadings. Collaborative projects, first for automotive applications SIKA with, and secondly with the CEA to characterize the mechanical behavior of the accession of insulating parts of high field magnets operating at cryogenic temperature (project Isolde / Inumac, postdoc 18 months), will be launched.
2. Modeling the influence of age in the marine environment on the behavior of bonded joints. In this study, it is necessary to analyze in detail the influence of surface preparation of substrates and primary used for sustainability on the mechanical behavior of the bonded assembly as a function of aging in humid environment. In particular, it may be necessary to propose a model of the interphase-substrate adhesive. A collaborative project with the DGA and Eurocopter is under study on this topic. Further work on the influence of hydrostatic pressure, in collaboration with Lucas da Silva University of Porto and Peter Davies, IFREMER is included in this framework. In addition, a collaborative project is being set up with Josef Raimund Rolfes and Matthias Volger of the "Institute of Structural Analysis, Leibniz University Hannover, 3D modeling of the behavior of composite joints (models taking into account The influence of hydrostatic pressure).

Study of the behavior of off-plan composite bonded joints and composites.

1. As part of the sequence of the thesis in collaboration with Airbus, a study in collaboration with Nicolas Carrère of ONERA is proposed for studying the behavior of bonded composite for aerospace applications. The objective is to establish a procedure for identifying reverse the degradation of the composite using the numerical models developed at ONERA.
2. We also propose to continue the study on optimizing the behavior of composite assemblies bios (with Yves Grohens and Christophe Baley, LIMATB, Lorient and Peter Davies, IFREMER).

For applications heavily used, the bonded assemblies are often proposed hybrid (bolted bonded assemblies for aerospace Airbus and Eurocopter, welded and bonded joints for automotive applications SIKA). A natural consequence of the proposed activated is associated with the optimization of these assemblies.

Modeling the behavior of mooring line at sea

(Participant: Guilhem Bles)

The offshore mooring lines are either chains or steel cables or cables son of woven polymer (often polyester). For large depths (2000, 3000 meters), steel lines are limited because of their weight becomes too great. The son of polymer lines then have a definite advantage because of their lightness. Unfortunately, the behavior of the latter is elastic and nonlinear viscous. What complicates the work of design engineers. The modeling approach developed to analyze the behavior of woven materials (viscoelastic anisotropic model) is a good basis for addressing the modeling of the behavior of synthetic cables. On this theme of collaboration with IFREMER are possible.

Implementation of composite materials by the method of infusion

(Participants: Franck Le Poulain, Eric Lolive, Bonnemains Thomas, Jean-Yves Cognard)

The objective is to establish a design tool and aid to the achievement which can determine the optimal parameters of implementation for obtaining materials free of defects and possess desired mechanical properties. To achieve this, we want to develop an experimental instrument to:

1. quantify and monitor throughout the infusion process of all parameters of implementation (flow of resin, depression ...)
2. to monitor the flow front in two dimensions in a first-time and three dimensions in a second time - in unsaturated and saturated regime by setting up a marker - to determine propagation speeds of resin,
3. measure the pressure field in different parts of mold unsaturated and saturated regime,
4. follow the evolution of geometry over time (unsaturated regime, the saturated regime, during and after curing).

Funding for the experimental device is being finalized in collaboration with the IUT de Brest (professional license "Design and manufacture of composite structures" and SYRTEF PFT).