A study of the impact of humid aging on the strength of industrial adhesive joints

Abstract

This paper aims at investigating the aging of a single lap joint (SLJ) in water at 70 1C. Experimental observations show an important decrease of deformability from 1 day of aging, while initial behaviour is not impacted. Further investigations reveal that the initial crack occurs at the interface near extremities of overlaps at a load depending from aging time. To predict the behaviour of the aged SLJ submitted to tensile loading, it is necessary to know precisely the state of stress in the adhesive layer and at the interface. The authors develop a finite element model to simulate the diffusion of water in the adhesive layer of the SLJ and the subsequent residual strength testing. The mechanical behaviour of the adhesive is predicted by a coupled elasto-plastic law which is deduced from an experimental work on bulk adhesive aged in water. It can model simultaneously its intrinsic behaviour as a function of temperature and water concentration and allow predicting the tensile tests on aged adhesive specimens and the volume change due to temperature and diffusion of water. Using the finite element software ABAQUS, the authors show that during diffusion of water, stresses can be important in the adhesive layer and can generate small damage. Then, for a load that led without aging to crack initiation and final fracture, stress field in the aged adhesive layer is not that critical. Such results tend to confirm that interface has been mostly impacted and weakened by water.

Experimental and numerical study on the effect of humidity-temperature cycling on structural multi-material adhesive joints

“…Small deformations of these adherends impacted negatively the internal pressure in bonds. Furthermore, this FE analysis outcome corresponds to the results reported in [14] and [20], showing great similarities in stress concentrations patterns in adhesive layers.…”

“…Also, apart from the experiments, an accurate analytical model was developed, capable of incorporating temperature effect to the joint strength evaluation. Leger et al in [20] described aging of specimens immersed in water, carried out on aluminum coupons. The authors reported that the initial cracks occurred in the vicinity of adhesive layer vertices and that the center of the joint was hardly reached by water molecules.…”

Joining of dissimilar materials

“…Further research is needed on this topic. The effect of ageing, which will lead to progressive degradation of mechanical properties of the adhesive joint, is also an important area of research [130].…”

Degradación ambiental y en condiciones adversas de adhesivos estructurales : análisis y consideraciones técnicas para su aplicación industrial

“…Leger et al [28] estudiaron el envejecimiento, mediante la inmersión en agua a 70°C durante periodos de 1, 5 y 14 días, de probetas a solape simple de acero unidas con epoxi. Los resultados indicaron que se producía una diminución importante de la deformación tras 1 día de envejecimiento, mientras que el comportamiento inicial no se ve afectado.…”

“…Los acrílicos termoestables están formados por dos componentes y consiguen una elevada resistencia a cizalladura para muchos metales y plásticos. Debido a su rápido curado y a su alta resistencia (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), los acrílicos son utilizados en operaciones altamente automatizadas. Los acrílicos modificados tienen una buena resistencia al pelado, al impacto y a cortadura en un intervalo de temperatura entre -100° y 120°C.…”