Interface bonding strength measurement of a joint between elastic and viscoelastic materials

Measurement of bi-materials interface bonding strength is crucial for the design and application of structures with two or more materials since bi-material interface debonding is one of the major modes of failures for these structures. However, accurate determination of the interface bonding strength is not an easy task due to the discontinuity of material properties at the interface. There may exist a stress singularity at the edges of bi-material interface, where the debonding usually initiates from. A new specimen design that can eliminate the stress singularity is proposed. In practical applications, the interface failure often occurs under the actions of combined interface normal and shear stresses. Therefore, a biaxial normal-shear bonding strength envelope is required for practical applications. This paper presents a new experimental method integrated with finite element analysis and an iterative algorithm to determine the interface strength envelope between aluminum and epoxy polymer materials, in which the former is considered as an elastic isotropic material and the latter as a linear viscoelastic material.