Numerical analysis and optimization of adhesively-bonded single lap joints by adherend notching using a full factorial design of experiment

Abstract

The objective of this study is to carry out experiments using the experimental design methodology to determine the optimal geometric configuration which improves the resistance of a single-lap joint with notched adherends subjected to uniaxial tensile load. On the sides of the adherends in contact with the adhesive layer, a longitudinal rectangular notch is introduced. A complete experimental design (15) of three factors at two levels: the adhesive thickness (tA), depth (dN) and extended length (LE) of the notch was used to determine their effects on strength of an adhesive joint. The response or dependent variable used was the resistance of a single lap joint (SLJ). Finite element (FE) analysis was conducted to investigate the effect of different notch parameters on the strength enhancement of the SLJs. A quadratic regression model with interaction is developed to relate the strength of an adhesive joint and the variables (tA, dN and LE). The regression model was validated using various statistical approaches. According to the ANOVA results, the model is highly significant and in good agreement with the experimental results. The quadratic regression model suggested was used for optimizing the resistance of the joint. The maximum joint strength occurs when the adhesive thickness is the smallest (left end) and when the adhesive thickness is the largest (right end) of the validated domain. The strength of SLJ increases when the notching parameters (dN and LE) increase in the validation zone. The numerical results show that to improve the resistance of an adhesive joint with notched adherend, it is necessary to minimize the thickness of the adhesive layer and to use notch with the highest depth and extension equal or greater than the overlap. The results show that using the adherend notching can significantly improve the load bearing capacity of SLJs.