Adhesive joining techniques have rapidly gained momentum in the automotive industry over the past decade, offering several advantages over traditional joining methods. The complex design requirements of modern automobiles have increased the demand for intricately shaped components, where conventional spot/seam welding and mechanical fastening are often not feasible.
Unlike spot and arc welding, adhesives do not degrade the properties of the substrate. Moreover, they enable the joining of components made from dissimilar materials, thus contributing to the overall weight reduction of assemblies. Adhesives also provide damping effects, reducing noise, vibration, and harshness (NVH), thereby contributing to a quieter and more comfortable ride. Additionally, adhesives enhance structural integrity by distributing stresses more uniformly across the joints. Consequently, understanding the simulation and failure prediction of adhesive joints has become essential.
Traditional failure criteria such as maximum stress, maximum strain, maximum principal stress/strain, and plastic yielding have limitations in accurately predicting adhesive joint failure due to inherent stress singularities. The Cohesive Zone Model (CZM) provides better insight into the behavior of adhesive joints, enabling the simulation of crack initiation and propagation, including multiple crack paths within a single model.
There are three independent failure modes in adhesively bonded joints. The crack opening mode (Mode I) is considered more critical than in-plane shear (Mode II) and out-of-plane shear (Mode III) since its fracture toughness is typically lower.
This paper investigates the tensile and shear moduli of adhesive materials, evaluates traction-separation behavior, and explores fracture energies across Modes I, II, and III. It emphasizes the accurate modeling of adhesive joints using cohesive elements to simulate crack initiation, propagation, and eventual failure. The methodology is validated against experimental data, demonstrating its effectiveness in predicting the performance and durability of adhesive joints.