Numerical study of an arcan tensile compression shear test in dynamic: application to bonded joints

This paper presents a numerical study of the Arcan TCS testing device under dynamic conditions. This test is commonly used to characterize the mechanical behavior of bonded joints subjected to combined quasi-static loadings. In this study, the question of its extensibility to dynamic loadings by the use of an impactor guided in a drop tower is investigated. A dedicated finite element model is built under the plane stress assumption. Stress distributions in the adhesive are analysed trought time ans space for several configurations

Modelling edge effects at the interface in bonded joints using gradient functions in the mechanical properties of the adhesive: Application of the method to the Arcan test loaded in tension and shear

International audienceThe design of bonded joints requires studies of stress concentrations due to edge effects. For complex joint configurations, the finite element method can be quite costly. The objective is to develop a fast and reliable numerical design tool for bonded assemblies. Therefore, an approach to design bonded assemblies is presented which aims to meet the needs of a design office, particularly in terms of calculation costs. The latter consists in reproducing the edge effects with a single element through the joint thickness using a modulus function. The concept was tested on Arcan specimen with two loading cases: tension (γ = 0°) and shear (γ = 90°). A 2D model under the elastic assumption is developed to describe the edge effects of the joint using Abaqus subroutines (UMat). The approach is set up to solve this problem in the form of two blocks. First, mesh refinement studies for bonded specimens loaded in tension were performed, within a good level of accuracy, on the free edge with the use of local discretization error estimation. After that, the effects of local geometry and modulus ratio are investigated. Afterwards, the von Mises stress at the interface level of the adhesive joint was used to identify a modulus function to describe the behavior of a joint with straight edge geometry for tension and shear loadings. The proposed approach has improved the performance of the model. Actually, the calculation is practically three times faster than for the conventional model

Polychloroprene behaviour in a marine environment: role of silica fillers

International audiencePolychloroprene rubbers are widely used in marine structures and often filled with silica in order to increase mechanical properties. The presence of silica fillers leads to a complex degradation of the material. This study aims to understand the deeper degradation mechanisms involved when a silica filled polychloroprene is used in sea water. To do so, 4 polychloroprene rubbers filled with different amounts of silica (from 0 to 45 phr) were aged in natural sea water for 6 months at temperatures ranging from 25 to 60 degrees C. Moreover, a natural rubber with similar formulation was also considered in order to evaluate the role of the chlorine atom in the degradation. The chemistry and mechanics of the rubber degradation were also studied. In the presence of water and silica fillers, a large decrease in rubber stiffness was observed. This was attributed to the breakage of hydrogen bonds involved in the interaction between the silica and chloroprene matrix and the process is reversible. In the meantime, silica undergoes hydrolysis that leads to silanol formation and so an increase in rubber stiffness when water is removed; this process is irreversible