20 Juillet – Thesis defense - Justine Bertrand

12 h Amphi La Rochefoucauld-Liancourt (Campus Arts et Métiers Bordeaux-Talence)

Ageing of bonded joints undershear loading.

This thesis deals with ageing of bonded joints under shear loading. The bonded joint technique competing with riveting, welding or folding methods,
has sealing properties, allow to put together structures with complicated shapes and made with dissimilar materials and can be adapted for various environmental conditions. Bonded joints are generally designed to withstand shear loads. However, this technology is not competitive yet for applications which require a high level of reliability : complex loading (creep, quasi-static, impact, ...) coupled with an aggressive physico-chemical environment (temperature, humidity, ....).
The main objective of this thesis is to evaluate the mechanical behaviour of bonded joints under shear loading in order to enhance the robustness of the methods for predicting the behaviour of bonded joints. To address this issue, two test procedures using Digital Image Correlation (DIC) were developed to assess the mechanical behaviour of bonded joints: the Arcan test was used to identify the rheological behaviour of the adhesive layer and the End Loaded Split (ELS) test was used to observe damage evolution in the adhesive layer. Then, an experimental method was described to directly identify the shear behaviour of the adhesive layer (cohesive law). This law is the first input in simulation tools (analytical or numerical) that can predict the mechanical behaviour of bonded joints. Eventually, a semi-analytical model was developed which is able to predict the behaviour of the bonded joint (adherend displacements, shear strain and stress in the adhesive layer) under shear loading in a standard environment (ambient temperature and humidity and quasi-static loading).

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