In-service behavior, durability and lifetime

During its service life, the structure is subjected to a series of natural or accidental stresses of all kinds. All of these stresses and their coupling can be applied to the structure.

Gradients – chemical concentrations, humidity, pressure, etc. – between the material and its environment are at the origin of material exchanges that are often detrimental to the reliability of structures. Indeed, the structural material often also plays a role of diffusive “barrier”. Concrete structures are directly exposed to aggressive agents (CO2, chlorides, acids, sulfates, biofilms, etc.), the role of the coating is to protect the steel reinforcements from corrosion. When the diffusing element reacts with the medium in which it moves, it is called reactive transport. In this case, the phenomenon modifies the chemical composition and the microstructure of the materials (dissolutions, precipitations) and even its state of stress. Moisture gradients affect most porous and polymeric materials, with shrinkage/swelling phenomena and associated stresses. The study of hygrothermal transfers is then necessary to understand the behavior of materials and qualify innovative solutions. We note indeed a strong coupling with the mechanical field in some materials, for example with the phenomena of mechano-sorption in the case of natural fibers.

At the scale of the structure, the static or cyclic load, as well as the combination, of external mechanical solicitations and/or environmental actions is likely to aggravate the consequences of these – the damage and the cracking accelerate the transport of material towards the vulnerable zones of the structure (corrosion) – but sometimes also to mitigate them (healing).

The maritime environment represents a particular interest and aggressiveness for composite materials in the broadest sense – reinforced concretes, organic matrix composites, bio-sourced materials, membrane structures, bonded assemblies – and is an important issue for the GeM ecosystem, with the proximity of the Atlantic Ocean and the ongoing development of marine renewable energy (MRE).

The development of this axis will be pursued in collaboration with the other TRUs, relying on innovative experimental equipment and multi-physics and multi-scale numerical modelling/simulation. The scientific developments will aim at :

– better understand and predict degradation mechanisms,
– rationalize the experimentation for the study of the long-term behavior of evolving materials with non-linearities: fatigue of synthetic anchor cables and energy transmission cables, creep, cracking and swelling of cementitious and composite materials,
– characterize the interactions between the structure of materials, mechanical loads and environmental actions, in order to identify possible couplings,
– develop a performance approach to durability.

This approach allows to qualify a material for a given environment on the basis of aging tests and durability indicators. These performance specifications will allow the qualification of innovative materials developed in response to societal issues.

Physico-chemical gradients and transport

Chemical (water, chlorides, CO2, etc.) and physical stresses (UV, thermal, fire, etc.)

Hygrothermal
aging

Composites and assemblies,
Ecomaterials


Mechanical
stresses

Long-term behavior
Fatigue, creep, etc.


Couplings

Damage and diffusion, durability


FACILITIES

  • Numerical methods: numerical and analytical homogenization of physical and mechanical properties, molecular dynamics,
  • Accelerated ageing chambers, tidal and salt spray simulator
  • Mechanical testing platforms – creep, fatigue, fracture – and associated instrumentation: acoustic emission, image correlation
  • Characterization means : microstructure, mechanical and transfer properties of cement materials
  • Optical platform
  • Microscopic observations: SEM-EDS, microtomography.

ONGOING PROJECTS

  • Study of synthetic anchor cables for floating wind turbines (2022-2025)
  • MONAMOOR – Monitoring of polyamide mooring lines (2020-2024)
  • CEAUCOMP – Modelling of coupling between water diffusion and mechanical loading in composite materials (2018-2021)
  • FIRMAIN – Impact of hygroscopic aging on the carcking of composite materials in an uncertain context(2016-2020)
  • Projet National PERFDUB – Performance-based approach of durability of concrete (and concrete structures) (2015-2022)

MEMBERS

Coming soon…

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