Analysis of the state of deformation and internal damage in cement matrix composites used for reinforcement of civil engineering structures
Composites with a cementitious matrix and textile reinforcement by their mechanical, environmental and aesthetic compatibility are used on a large scale for the rehabilitation and reinforcement of built heritage and civil engineering structures.
Under the effect of mechanical or environmental stresses, the phenomena of interaction and damage between the textile reinforcement and the cementitious matrix prove to be more complex than in the case of polymer composites. These are mainly related to the fragile, cracking nature of the matrix and a reinforced / matrix bond of mechanical preponderance. In particular, knowledge and understanding of charge transfer mechanisms between fiber / reinforcement and matrix and initiation and cracks remain a major scientific lock.
Current measurement techniques (mechanical extensometry, digital image correlation techniques -DIC, etc.) are able to give information on the state of deformation and stress of the surface of the test body. The different mechanisms of stress and degradation of the components (fibers, matrix) are deduced using the approaches of the continuum mechanics and of the rupture.
In this context, we propose in the framework of this thesis to set up and adapt measurement systems that can be integrated within composites (for example, optical-fiber sensors, integrated resistive sensors). The main objective is to analyze more precisely the mechanical parameters on the micro scale and the mechanisms of transfer of charge, initiation and propagation of cracks as well as mechanisms of damage. On the basis of a uniaxial or biaxial traction test coupled to the chosen instrumentation, a methodology to identify local laws of fiber-matrix interaction (slip, damage, etc.) will be implemented. The purpose of the thesis work will be to determine the material parameters of the composite (deformation gradients, stress concentrations, etc.) and to establish the mechanical parameters characteristic of the local behavior (cracking, damage, behavior of the interfaces, etc.). ) and global (laws of behavior, …). The results will be used for the construction and improvement of mechanical models of the stiffness and rupture behavior of composites with textile reinforcement and cement matrix.
- Aron Gabor
Beginning and end of the PhD thesis
01/10/2017 – 30/09/2020