Effect of Adhesive Thickness on Cohesive Laws of Adhesively Bonded Joints

Abstract

In the past several decades, cohesive zone models (CZMs) have been widely utilized for understanding fracture of adhesively bonded structures including adhesively bonded joints due to its fairly simple and accurate predictive ability. In CZMs the nonlinear interfacial fracture behaviors are described by the traction-separation laws (also referred to as cohesive laws). The cohesive laws represent the local constitutive behavior of the adhesive layer, instead of the global parameter, such as toughness. Obviously, the properties of the adhesive layer, including strength, stiffness, toughness, bond strength, and thickness, play an essential role in the fracture of the bonded structures. In this chapter, within the framework of nonlinear fracture mechanics, we will summarize our experimental studies on the effect of adhesive thickness on the CZM under pure Mode-I (peel fracture), pure Mode-II (shear fracture), and mixed Mode I/II fracture modes. The experimentally determined interfacial traction-separation laws provide valuable baseline data for parameter calibrations in numerical models. The experimental results may also facilitate the understanding of adhesive thickness dependent interfacial fracture of bonded joints.