21 Janvier – Thesis defense - Tanguy Briand

10 h Amphi 3 - IUT of Bordeaux (Gradignan)

Characterization and modelling of the relationship between damage and permeablity in laminated composites with cryogenic conditions.

The design of liner-less cryogenic tanks for the space launchers require to identify accurately the complex and multi-scale behaviour just as the permeability of the composite laminate according to the thermomechanical loading because of the liquid propellant and the pressurisation. The objectives of this study is to propose a damage and leak path predictive meso-model according to the loading applied to the structure. The meso-model is build and enhanced from several experimental protocols to characterise the composite laminate behaviour. First, this research work aim to develop these ambient protocols to the low temperatures. Under-load microscopic observations and X-tomography are used on straight specimen to identify and quantify the transverse cracking process and especially the interaction phenomenon between the damaged plies that pilot the appearance of the first leak path. In addition, two experimental tests is developed on tubular specimen to measure the permeability of the material and the leak path localisation under uni-axial and bi-axial loading. To complete and confirm the experimental observations, we propose a strategy based on the cohesive zone to model the discrete damage of the laminate at the mesoscopic scale. Finally, the proposed predictive meso-model based on a scale changing with an energy equivalence to predict the transverse cracking process is extented to the low temperatures. The interaction effects are included with a phenomenological approach in order to predict the rate of leak path. A confrontation between the model and an industrial application representative test allows evaluating of the implemented strategy relevance.

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