The Effect of Adhesive Layer Thickness on Joint Static Strength

Abstract

One of the most relevant geometrical factors defining an adhesive joint is the thickness of the adhesive layer. The influence of the adhesive layer thickness on the joint strength has not been precisely understood so far. This article presents simplified analytical formulas for adhesive joint strength and adhesive joint coefficient for different joint loading, assuming, inter alia: linear-elastic strain of adhesive layer, elastic strain of adherends and only one kind of stress in adhesive. On the basis of the presented adhesive joint coefficient, the butt joint was selected for the tests of the influence of adhesive thickness on the adhesive failure stress. The tests showed clearly that with an increase in the thickness of the tested adhesive layers (up to about 0.17 mm), the value of their failure stress decreased quasi linearly. Furthermore, some adhesive joints (inter alia subjected to shearing) may display the optimum value of the thickness of the adhesive layer in terms of the strength of the joint. Thus, the aim of this work was to explain the phenomenon of optimal adhesive layer thickness in some types of adhesive joints. The verifying test was conducted with use of single simple lap joints. Finally, with the use of the FE method, the authors were able to obtain stresses in the adhesive layers of lap joints for loads that destroyed that joints in the experiment, and the FEM-calculated failure stresses for lap joints were compared with the adhesive failure stresses determined experimentally using the butt specimens. Numerical calculations were conducted with the use of the continuum mechanics approach (stress-based), and the non-linear behavior of the adhesive and plastic strain of the adherends was taken into account.

Numerical and experimental study on protective film removal towards the automation of flexible electronics assembly

“…Figure 11a shows that as t A increases, the peeled area rate decreases. This behavior can be explained by the fact that the trigger load increases with increasing adhesive thickness, especially in the range of 0.01-0.08 mm, as reported by Roskowicz et al in [23]. The results also reveal that the robot approaching velocity v R does not influence the PA; thus, it can be reasonably set at high values in order to reduce the task execution time.…”

Ultrastrong underwater adhesion on diverse substrates using non-canonical phenolic groups

“…The compression of the adhesive layer is considered to be the reason for the improvement of adhesion strength. The previous report showed that thin adhesive layers are more beneficial than thick ones 32 , and larger quantities did not increase the adhesion strength of our system (Supplementary Fig. 40 ) as the adhesive layer became thick.…”

Improved Copper–Epoxy Adhesion by Laser Micro- and Nano-Structuring of Copper Surface for Thermal Applications

“…It is also important to bear in mind that despite the uniform applied pressure to the joint during curing, it is not possible to guarantee an exact uniformity of the adhesive layer thickness among all tested joints. The effect of the adhesive thickness on bond strength, which would depend on the epoxy mechanical characteristics and on the type of joint, is complex and not yet fully understood [ 28 , 29 , 30 ]. Large variations on the adhesive thickness may even produce changes on the cohesive/adhesive failure mode [ 28 ], although this is not expected to occur in the present work, given the above-mentioned thickness range measured in selected joints of this study.…”