The Effect of a Hot–Wet Environment on Adhesively Bonded Joints Under a Sustained Load

Abstract

The aim of this research was to develop numerical modelling techniques for simulating the simultaneous effects of moisture, elevated temperature and applied load on the performance of adhesively bonded joints. Associated experimental data are also reported. The degradation process of the joints was modelled using a fully-coupled approach, with the moisture concentration affecting the stress distribution and the stress state affecting the moisture diffusion analyses simultaneously. Further, the stress analysis contains a moisture dependent creep model to accommodate viscous effects and both swelling and thermal strains were included in the simulation. The governing parameters adopted in the modelling procedure were determined from experimental work based on the bulk adhesive. The joint response was monitored throughout the ageing process and good correlation was found between the experimental and numerical results.

The strength prediction of adhesive single lap joints exposed to long term loading in a hostile environment

“…This is reasonable because, as with the experimental data, by the time the transition creep strain has been reached the adhesive will generally be in a saturated condition. Good correlation was found between the predicted and experimental creep behaviours in the SLJs as presented elsewhere [32].…”

“…Detailed verification and discussion of the modelling technique have been reported elsewhere [32], however major modelling achievements in Step 1 are presented in Section 5.1 to provide a better understanding of the whole modelling work. Following this, the majority of this section focuses on the SLJ simulation results from Step 2 (the residual strength modelling) to investigate the degradation in joint strength induced by the prior simultaneous exposure to moisture and sustained loading.…”

“…Modelling details related to Step 1 can be found elsewhere [32] and this paper focuses on the modelling procedure performed in Step 2. However, key data from Step 1 will be presented.…”

“…It is worth noting that although the stress states in the bulk adhesive and adhesive layer in the joint are different, as a starting point the von Mises stress was used to characterise the stress dependence of the moisture uptake. This procedure was carried out in Abaqus and has been discussed in detail elsewhere [32].…”

“…It can be seen that the degraded i) elastic stiffness K, ii) tripping traction T and iii) fracture energy Gc, (which constitute a set of CZM parameters) are dependent on the prior ageing (moisture and loading level) experienced. Using the data transfer procedure outlined in Section 4.4, the DF (moisture uptake and equivalent creep strain) distribution in the aged adhesive layer was determined and transferred from the validated simulation in the Step 1 model [32] into the Step 2 model. Finally the quasi-static tensile testing of the degraded aluminium SLJ was simulated numerically using progressive damage FE modelling to obtain the predicted residual strength after ageing.…”