Experimental study of the impact of chamfer and fillet in the frontal edge of adherends on the fatigue properties of adhesive joints subjected to peel

Abstract

The paper presents the influence of simple structural modifications of the adherend on the fatigue properties of adhesive joints subjected to peel. The considered modifications consisted in making a chamfer and fillet on the front edge of the adherend. The purpose of such modifications was to locally increase the thickness of the adhesive layer in the area of stress concentration. Fatigue strength tests were carried out using an electrodynamic shaker at the resonant frequency of the flexible adherend. On the basis of fatigue strength tests carried out at the limited number of cycles equal to 2×106, it was shown that a local increase in the thickness of the adhesive layer in the front part of the joint allows a significant increase in the joint's fatigue lifetime and fatigue strength. The greatest effect was shown for the variant with the fillet R2. In this case, an increase in fatigue strength of 33.1% compared to the base variant was demonstrated. For the fatigue stress level of 20.25 MPa, an increase in fatigue lifetime of 337.7% was also demonstrated. Based on the conducted research, it was shown that the reason for the improvement of the fatigue properties of the joints due to the local increase in the thickness of the adhesive layer is the phenomenon of energy absorption in the frontal area of the joint. Absorption of energy that inhibits the process of fatigue results from, among others, local flexibility of the joint, as well as nucleation of cracks in the locally increased volume of the adhesive.

Selected Methods of Modifying the Surface Layer of a Carbon Composite

“…The use of such techniques results in an increase in surface roughness [5,17], and thus an increase in the strength of the adhesive bond. Many studies indicate that the properties of adhesive joints depend on a number of key factors, and these include [18][19][20]: type of adhesive [21], type of hardener, surface condition, adhesive application method, application conditions (temperature, humidity and adhesive open time), curing conditions, operating environment, chemical resistance and joint geometry [22][23][24][25].…”