Fracture Behaviour of Adhesives Modified With Various Rubber Content Under Combined Stress Conditions

Rubber-modified adhesives have attracted special interest recently due to their property of dramatically increase in fracture toughness of adhesively bonded joints, where the fracture toughness increases with the rubber content. However, an increase in rubber content decreases the joint strength without initial flaws. Besides, most adhesively-bonded joints have combined normal and shear stresses concentrated in the adhesive layer. Hence, the effect of rubber content on adhesively-bonded joints should be clarified under combined stress conditions. In this paper the aim is to characterize the rubber content dependent behaviour of the rubber-modified adhesive under combined stress conditions. Tensile tests were conducted for adhesively-bonded butt and scarf joints with various rubber contents, where these joints can cover the combined stress conditions in the adhesive layers of most joints in industrial applications. The influence of the rubber content on the joint strength is represented in the normal stress-shear stress diagram.