Optimization and Analysis of Adhesive Joints with Modified Geometries for Reducing of Adhesive Consumption

Abstract

Adhesive bonding is a joining method frequently used as an alternative to mechanical fasteners. Compared to mechanical joints, adhesive bonding offers significant advantages such as reducing stress concentration and avoiding damage to the materials being joined (e.g., no need for drilling or riveting). Adhesively bonded joints, which rely on cohesive and adhesive forces, are particularly well-suited for the aerospace industry, where weight reduction is of critical importance. In a study conducted by James Renton et al., it was shown that, unlike mechanical joints, adhesive bonding results in a more uniform distribution of shear stress [1]. Typically formed using synthetic-based two-phase materials, these non-detachable joints are created by applying a thin layer of adhesive between the substrates. The adhesive undergoes a chemical reaction and cures to form a permanent bond. In this study, auxetic patterns were used in the bonded joints as a method for weight reduction. The aim of the research is to design weight-reducing adhesive patterns and investigate the mechanical properties of the resulting bonded joints. Despite reducing the weight by auxetic patterns, it is expected that stress concentrations can be minimized and the loss in strength can be kept to a minimum. In a study conducted by Armenio N. Correia et al., it was concluded that, from a mechanical behavior perspective, adhesive joints with high ductility—when well-designed in terms of process parameters and appropriate adhesive type—can outperform traditional mechanical joints [2]. In the present study, the adhesive joints were designed as single-lap joints, and the 3D printing parameters for PLA were kept constant. The effect of adhesive reduction via auxetic patterns on the tensile strength of the joints was analyzed. Auxetic materials are those that exhibit a negative Poisson’s ratio. Unlike conventional materials, which become thinner when stretched, auxetic materials expand laterally when subjected to tensile loading. When a material shows an increase in thickness rather than thinning during tension, it is referred to as auxetic.