These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Cohesive zone modeling is a powerful tool for simulating the failure of adhesive joints and adhesively bonded interfaces. Accurate simulation of adhesive or interface failure with cohesive zone modeling requires simulation engineers to define traction-separation laws that describe the stiffness, strength, and toughness of the adhesive or interface under tension, shear, and mixed-mode loading. These parameters are not generally available from data sheets or other references and so the CZM parameters have to be determined experimentally on a case-by-case basis. Calibration of cohesive zone models is often done using standard test specimens to measure the strength and toughness of the adhesive or interface. Standard fracture mechanics tests specimens can also be used to directly measure the traction-separation law for an adhesive bond. This works particularly well for ductile structural adhesives. However, in many cases, the use of standard test specimens or established CZM calibration methods is not possible. Cases like this arise when there are size constraints on material samples or if the materials being bonded are prone to large inelastic deformation during testing. Also, standard test methods are often not applicable for cases of high-rate or impact loading. When standard test methods aren'™t applicable, inverse calibration can be used to determine CZM parameters. Inverse calibration involves designing custom mechanical test specimens and loading fixtures along with using FEA to simulate the test. The CZM parameters are then iteratively solved for until good agreement between the measured and simulated adhesive or interface failure are in good agreement. In this presentation, we will discuss inverse calibration strategies for cohesive zone modeling that we have successfully employed for a variety of material systems. We will focus on addressing two commonly encountered scenarios: 1) when the materials being bonded are thin and 2) when the adhesive is being loaded under impact conditions. This talk will be of interest to simulation engineers responsible for modeling the failure of adhesive joints or bonded interfaces and are interested in new approaches to calibrate cohesive zone models.