a b s t r a c tThe stress singularity that occurs at a vertex in a joint with a slanted side surface is investigated. The orders of stress singularity at a vertex and at a point on stress singularity lines for various material properties are determined using eigenanalysis. The stress distribution on an interface and the intensity of stress singularity at the vertex are investigated using BEM. It is shown that the order of stress singularity at the vertex in the joints can be reduced by slanting a side surface so as to decrease the angle between the interface and the side surface. The results of BEM analysis reveal that the distribution of stress on the interface is influenced by the slanted side surface. Finally, the 3D intensities of the singularity for stress components which are continuous at the interface are newly defined and determined for various material combinations.

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In real practice, adhesively bonded structures are usually exposed to cyclic environmental conditions. However, cyclic ageing processes are relatively unexplored. The aim of this study is to consider the effect of cyclic ageing on the rate of water uptake and the drying process in an epoxy-based adhesive. Fick’s law was considered to estimate the water diffusion coefficients for the ageing and the drying steps at different cycles. Different cyclic ageing times have been considered in the ageing procedure. Dogbone shape specimens were also manufactured and subjected to cyclic aging to investigate the tensile properties of the tested adhesive as a function of aging cycles. The gravimetric results showed that the rate of water uptake and drying is mainly a function of the level of water uptake of the first ageing cycle. Tensile test results showed that the maximum water content increases with each subsequent ageing cycle. It was also found that the Young’s modulus and the tensile strength of the adhesive decreased significantly after the initial ageing cycle, but all subsequent ageing cycles have considerably less influence on the mechanical properties of the adhesive.

The strength and durability of adhesive joints are significantly influenced by environmental conditions. Humidity absorption can cause deleterious effects on the adhesive joint's performance. The current study investigates the tensile properties of an epoxy‐based adhesive using Arcan joints (which is a kind of butt joint) subjected to different aging levels and loading conditions. To this end, joints with different aging times, as well as reference‐dried samples, were subjected to both the static and cyclic loading conditions. To construct the S–N curves, different cyclic load levels were applied to the joints. The static results showed that the mechanical properties, such as tensile strength of the joints decreased with an increase of the aging time. The fatigue strength and the fatigue lifetime were significantly decreased by the increase of aging levels, mainly due to an interfacial aging phenomenon. The water diffusion in interfacial aging is faster than that of the adhesive aging, which resulted in a premature failure of the joints for both the static and fatigue conditions. Based on the experimental results, the interfacial diffusion coefficient was calculated using an inverse method. According to the results, the rate of water uptake along the interface is more than 30 times higher than that which occurs in the adhesive.

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