# Validated Cohesive Zone Models for Epoxy-Based Adhesive Joints Between Steel and CFRP Composites for Multimaterial Structural Design in Transportation Applications

## TL;DR

This paper develops and validates models for epoxy adhesive joints between steel and composite materials, enabling accurate simulation of structural failure in transportation applications.

## Contribution

The study introduces and validates cohesive zone models for epoxy joints between steel and CFRP, enabling reliable simulation of structural failure in multimaterial systems.

## Key findings

- Cohesive zone models for epoxy-based adhesive joints were calibrated and validated using Mode I and Mode II experimental tests.
- The validated models accurately predict failure initiation and propagation in adhesive joints under large deformations.
- The models were successfully applied in a bus rollover simulation, showing their relevance for real-world structural design.

## Abstract

This study presents the development, calibration, and validation of cohesive zone models (CZMs) for epoxy-based adhesive joints connecting stainless steel and CFRP composites. The objective of this study is to develop and rigorously validate cohesive zone models for epoxy-based adhesive joints between stainless steel and CFRP composites, ensuring their reliability for numerical simulations of structural failure under quasi-static and large-deformation conditions. The work focuses on accurately describing the quasi-static behaviour and failure mechanisms of hybrid adhesive interfaces, which are crucial for multimaterial structures in modern transportation systems. Experimental tests in Mode I (DCB) and Mode II (ENF) configurations were performed to determine the cohesive parameters of the structural adhesive SikaPower 1277. The obtained data were further analysed through analytical formulations and validated numerically using PAM-CRASH. Excellent agreement was achieved between experiments, analytical predictions, and simulations, confirming the reliability of the proposed material definitions under large deformations. The validated models were subsequently implemented in a large-scale numerical simulation of a bus rollover according to UN/ECE Regulation No. 66, demonstrating their applicability to real structural components. The results show that the developed cohesive zone models enable accurate prediction of failure initiation and propagation in adhesive joints between dissimilar materials. These findings provide a robust foundation for the design of lightweight, crashworthy structures in transportation and open new perspectives for integrating epoxy-based adhesives into additively manufactured hybrid metal–composite systems.