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Vieillissement hygrothermique d'un assemblage acier galvanisé/adhésif époxy : évolution de la tenue mécanique en fonction de l'état physico-chimique de l'adhésif

Julie Bertho 1
1 Procédés et performance des polymères et composites
PIMM - Laboratoire Procédés et Ingénierie en Mécanique et Matériaux
Abstract : During hydrothermal ageing of bonded assemblies for automotive industry, several phenomena overlap, with various kinetics: adhesive degradation, polymer/metal interphase strength and its hydrolysis, substrate corrosion. All these phenomena, occurring over the hydrothermal ageing of a galvanized steel/ epoxy-dicyandiamide adhesive joint, have a physico-chemical background. Thus water spread into assemblies is at the beginning of these events, notwithstanding, chemical reactions kinetics is the one which will rule the speed of adhesive joints mechanical properties decline. A multi-scale approach has been set up to have a better understanding of ageing phenomena at the local scale of the adhesive joint. This study highlights that the loss of mechanical properties is directly related to the adhesive chemical evolution and at long term, to the substrate corrosion. The chemical evolution of the adhesive has for major origin, the hydrolysis of imine bonds in the polymer network, assisted by the adhesive plasticization. Then, a pseudo-linear relationship has been established between the variations of the adhesive BM 1480R chemical structure and the decrease of the ultimate stress in assemblies. For a physico-chemical state of the aged adhesive, failure envelops are plotted and allow to estimate the galvanized steel/epoxy adhesive joint mechanical behaviour at failure, under mixed-modes of loading.
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Julie Bertho. Vieillissement hygrothermique d'un assemblage acier galvanisé/adhésif époxy : évolution de la tenue mécanique en fonction de l'état physico-chimique de l'adhésif. Matériaux. Arts et Métiers ParisTech, 2011. Français. ⟨NNT : 2011ENAM0028⟩. ⟨pastel-00655855⟩

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