Investigation on Delamination Characteristics of 2-Ply Clad Metals and Adhesive Joints for Aluminum/Stainless Steel via the Peel Test

Bonding properties are important for metallic multilayer composites (MMCs) comprising different materials or materials with different mechanical properties. In this study, we fabricated 2-ply Al/stainless steel (STS) clad metals and Al/adhesive (adh)/STS joints. To manufacture samples with various mechanical properties, T6 heat treatment was performed on clad metals, and adhesive joints of several thicknesses were prepared. For each sample, the bonding strength was characterized via a T-peel test and the results were analyzed using the peeling angle. For 2-ply Al/STS clad metals, the T6 heat treatment resulted in opposite trends in the mechanical properties. The bonding strength of 2-ply Al/STS clad metals was affected by the peeling angle, i.e., a small peeling angle provided a small bonding strength at the interface. However, for the 2-ply Al/adh/STS joints, the bonding strength of adhesives on metals depended on each adherend of the stress state. As the difference in mechanical properties between the two adherends increased, the difference in each peeling angle of Al and STS also increased. The peeling angle of adherends reached a limiting value when the sample contacted the clamping jig head; therefore, a new term, apparent bonding strength (ABS), is necessary to differentiate this new strength from the bonding strength obtained under non-contact conditions. We believe that the concept of peeling angle and ABS proposed herein will play a crucial role in describing the delamination behavior and bonding strength of MMCs via the peel test. Graphic Abstract