Effect of Loading Rate, Temperature and Adhesive Bondline Thickness on the Mechanical Response of Dissimilar CFRP-Steel Single Lap Joints Bonded with Flexible Adhesive

Abstract

The impressive properties of composite materials have allowed their integration in various structural and light weight applications. This large dependence on composites has resulted in multiple situations where bonding with other materials is required. Of the possible bonding mechanisms, adhesive bonding offers significant advantages such as eliminating stress concentration sites and the ability to bond brittle material. Single lap joints are considered a simple and efficient joining configuration that allows the bonding of two materials along an adhesive overlap. Consequently, analyzing the performance of single lap joints that incorporate composites bonded to different materials is highly important.

The performance of dissimilar CFRP-Steel single lap joints was investigated under variable operating conditions (testing temperature, loading rate) and adhesive bondline thickness. All joints were fabricated using a simple mold design that allowed the production of consistent lap joints with precise bondline thickness. Experimental results showed a general decrease in single lap joint shear strength at elevated temperatures; however, the strain rate effect was more evident upon increasing the temperature within the adhesive’s heat resistance range resulting in enhanced single lap joint shear strength. Furthermore, analysis of variance (ANOVA) results show that testing temperature has a larger contribution to the lap shear strength compared to the loading rate. On the other hand, the lap shear strength decreased progressively with the increase in bondline thickness.

Finally, a material characterization process was performed to extract the hyperelastic parameters of the flexible adhesive understudy, particularly Mooney-Rivlin and Neo-Hookean parameters. A hyperelastic numerical model was then established and showed impressive accuracy in replicating the experimental and analytical results for a selected case study of operating conditions.