Digital Image Correlation Measuring of Strain and Stress Distributionon Mixed Adhesive Joints Bonded by Honeymoon Adhesion Using TwoTypes of Second-Generation Acrylic Adhesives of Two Components

Abstract

For stress relief in the adhesive layer, various methods have been proposed, including the use of scarf joints. However, these techniques are highly dependent on the adherend thickness and are thus of limited use. The stress concentration of the joints can be relaxed by using mixed adhesive joints (MAJs), which employ a brittle adhesive in the middle portion of the overlap and a ductile adhesive at the bondline ends. In a previous paper, we proposed a manufacturing method of adhesive joints that have a variable modulus adhesive layer. When using the proposed method, adhesive flow has a significant effect on the adhesive layer property distribution. Considering adhesive flow using finite element analysis or numerical analysis is difficult. Therefore, an experimental evaluation is necessary to elucidate the actual behaviors of these joint types. The principal aim of this study was to investigate the relationship between applied patterns of brittle and flexible adhesives and the stress distributions of those adhesive layers. Accordingly, stress distributions of single lap joints were evaluated by a tensile test using a digital image correlation (DIC) method. Based on the DIC results, MAJs contributed to the relaxation of the adhesive layer stress concentration. According to the results of the adherend strain distribution, the longer was the soft type of adhesive, the wider was the stress concentration area.