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Characterization and modeling of multi-material assemblies under mixed quasi-static loadings for the design of automotive structures

Abstract : Nowadays, the emissions of CO2 due to the use of automobiles have reached critical levels causing global warming and health problems. In order to reduce these emissions, the French automotive industry has decided to reduce the car weight by means of the use of lighter materials such as composite materials. However, the classical joining techniques are not adapted to assembly these new materials to the structure of the car (aluminum and steel alloys). Therefore, the characterization and modeling of new joining techniques of dissimilar materials is a problem that has been treated in the current study.Four different joining techniques of dissimilar materials (metal/composite) have been studied: (i) stud bonding, (ii) laser welding, (iii) self-pierce riveting and (iv) adhesive bonding systems. Traditional lap-shear and cross-tension tests were used to characterize the first two joining techniques. Then, a new characterization test based on a modified Arcan device has been proposed to analyze the behavior of self-piercing rivet and adhesive bonding systems. Among all the four tested techniques, adhesive joints have been selected as the most adapted technique according to the requirements of the industry. Therefore, modified Arcan tests have been performed in order to determine the behavior of the adhesives of the study (Betamate1822 and Sikapower498). These tests were then used to propose and identify a new 3D non-linear viscoelastic spectral model. The identification procedure of the material parameters is only based on three multilevel creep tests, which permits the rapid dimensioning of adhesively bonded structures. Finally, the proposed behavior law was validated by the good concordance between the numerical predictions and the experimental curves of monotonic tests at different loading rates and increasing cyclic tests.The current study was developed in the framework of an automotive project. Nevertheless, the conclusions and prospects of the study can be extrapolated to other interesting fields.
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Submitted on : Wednesday, June 7, 2017 - 3:05:10 PM
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Hugo Leonardo Alfonso Medina. Characterization and modeling of multi-material assemblies under mixed quasi-static loadings for the design of automotive structures. Mechanical engineering [physics.class-ph]. Université de Bretagne occidentale - Brest, 2016. English. ⟨NNT : 2016BRES0118⟩. ⟨tel-01453047v2⟩

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