A discrete cohesive zone model for beam element: Application to adhesively bonded laminates and sandwich panels

TL;DR

This paper introduces a simplified discrete cohesive zone model for adhesive interfaces in laminates and sandwich panels, reducing computational complexity while maintaining accuracy, validated through multiple fracture tests and experiments.

Contribution

The novel DCZM simplifies interface modeling by treating it as a spring-beam system, reducing computational effort by over 25% without sacrificing accuracy.

Findings

Model is insensitive to element and load step size.

Reduces degrees of freedom by over 25% compared to existing methods.

Accurately predicts fracture behavior in laminates and sandwich panels.

Abstract

A new discrete cohesive zone model (DCZM) is presented for modeling the interface behavior of adhesive-bonded thin laminates and sandwich panels. The proposed model treats the interface as a spring element and the adherent as a beam element. The use of the preceding assumptions facilitates the simplification of the computational framework reducing the problem from a 2D to 1D, thereby relaxing the requirements of maintaining the aspect ratio of elements in the finite element mesh. For thin laminates, the constitutive relation of the adhesive is represented by a bi-linear traction-separation law, whereas for sandwich panels, an exponential law is employed to model the adhesive behavior. In order to validate the proposed model for thin laminates, simulations of three established fracture tests: DCB, ENF, and MMB have been undertaken. Additionally, for the sandwich panel, two experiments documented in the literature have been simulated for assessing the efficacy of the modelling. One experiment has a mode-I interface failure and the other one a mode-II interface failure between the core and skin. It has been observed that the model is not sensitive to either the element size or the load step size. The results have been compared with reported (benchmark) numerical, analytical, and experimental findings. The proposed methodology for thin laminates offers a significant reduction in the computational effort (reduced number of unknown degrees of freedom compared to existing methods) with no compromise on the accuracy of the predictions. Specifically, it reduces the unknown degrees of freedom by more than 25\% compared to the corresponding mesh used in existing continuum cohesive zone model (CCZM) approaches. The Newton-Raphson solver can achieve quick convergence and no line search feature is required. The proposed algorithm is easy to implement on any computational platform.