Estimation of fracture behavior of CFRP/CFRP adhesively bonded joints under mixed-mode conditions using a cohesive zone model

Abstract

Finite element (FE) simulations of adhesively bonded composite joints were conducted using the cohesive zone model (CZM). To clarify the effect of fracture criteria on the accuracy of the CZM simulation, two types of mixed-mode criteria including the ­linear summation model of Modes I and II energy release rates, $G_I/G_{\mathit{\text{IC}}}+G_{\mathit{\text{II}}}/G_{\mathit{\text{IIC}}}=1$, and the nonlinear power-law, ${\left(G_I/G_{\mathit{\text{IC}}}\right)}^n+{\left(G_{\mathit{\text{II}}}/G_{\mathit{\text{IIC}}}\right)}^n=1$ , were employed. A CZM formulation using the power-law fracture criterion was developed in this study. The load–displacement curves calculated by the two models were compared with the experimental results obtained from mixed-mode Fernlund–Spelt-type double cantilever beam tests, and the Mode II end-notched flexure (ENF) tests. Calculations using the nonlinear fracture criterion were closer to the experimental results. Consequently, it is concluded that nonlinear fracture modeling is of vital importance for accurate strength analysis of mixed-mode adhesive joints.

Keywords:

• Film type epoxy adhesive
• mixed-mode conditions
• cohesive zone model
• load–displacement curve
• power-law
• fracture toughness

Acknowledgments

We would like to thank Editage (www.editage.jp) for the English language editing.

Authorship contribution statement

Yousuke Kouno: Conceptualization, Methodology, Investigation, Data curation, Writing – original draft. Makoto Imanaka: Methodology, Validation, Writing – review and editing. Ryutaro Hino: Validation, Writing – review and editing, Resources. Masaki Omiya: Software, Formal analysis, Validation. Fusahito Yoshida: Validation, Writing – review and editing.

Disclosure statement

The authors have no commercial interest in any of the materials used in this study.