Abstract
With the increasing use of structures with adhesive bonds at the industrial level, several authors in the last decades have been conducting studies concerning the behaviour and strength of adhesive joints. Between the available strength prediction methods, cohesive zone models, which have shown good results, are particularly relevant. This work consists of a validation of cohesive laws in traction and shear, estimated by the application of the direct method, in the strength prediction of joints under a mixed-mode loading. In this context, scarf joints with different scarf angles (α) and adhesives of different ductility were tested. Pure-mode cohesive laws served as the basis for the creation of simplified triangular, trapezoidal and exponential laws for all adhesives. Their validation was accomplished by comparing the numerical maximum load (Pm) predictions with the experimental results. An analysis of peel (σ) and shear (τ) stresses in the adhesive layer was also performed to understand the influence of stresses on Pm. The use of the direct method allowed obtaining very precise Pm predictions. For the geometric and material conditions considered, this study has led to the conclusion that no significant Pm errors are incurred by the choice of a less appropriate law or by uncoupling the loading modes.
Highlights
The use of adhesive bonds in the aerospace, aeronautical and automotive industries, among others, has assumed a high preponderance to the detriment of conventional joining methods such as riveting, bolting, brazing and welding
The main purpose of this work was the evaluation of different cohesive zone models (CZM) formulations to predict the strength of adhesively-bonded scarf joints, considering the tensile and shear pure-mode laws were estimated by a direct method
The results showed that the mechanical behaviour of the scarf joints is dependent on the type of adhesive and value of α
Summary
The use of adhesive bonds in the aerospace, aeronautical and automotive industries, among others, has assumed a high preponderance to the detriment of conventional joining methods such as riveting, bolting, brazing and welding. Adhesive bonds offer several advantages such as the reduction of stress concentrations, good response to fatigue stresses, ability to bond dissimilar materials and lightness of structures. They present some limitations, namely the difficulty of disassembly, high cure times (in some cases) and limited temperature and humidity conditions [1]. There are several types of joint geometries, the most common are single-lap, double-lap and scarf [2,3,4,5].
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