Improvement of a Cohesive Zone Model for Fatigue Delamination Rate Simulation

Area of Science:

• Materials Science
• Mechanical Engineering
• Computational Mechanics

Background:

• The cohesive zone model (CZM) is widely used for simulating delamination and debonding.
• Existing CZM implementations for fatigue problems have limitations with high stiffness interfaces, such as ply-to-ply interfaces in composites.
• Previous work by the authors developed a CZM where damage affects cohesive stiffness.

Purpose of the Study:

• To develop a new cohesive zone model formulation that overcomes the limitations of previous models when simulating fatigue crack propagation in high stiffness interfaces.
• To enhance the accuracy and robustness of CZM simulations for delamination and debonding phenomena.

Main Methods:

• A new formulation of the cohesive zone model was developed.
• Finite element simulations were conducted on a mode I double cantilever beam (DCB) joint under constant bending load (constant G).
• The response of the new model was assessed against the original model for varying initial stiffness (K₀) and cohesive strength (σ₀).

Main Results:

• The modified cohesive zone model demonstrates robustness with respect to significant changes in initial stiffness (two orders of magnitude).
• The model also shows robustness when the cohesive strength is varied by a factor of two.
• The new formulation overcomes the inaccuracy issues encountered by the previous model with high stiffness interfaces.

Conclusions:

• The developed cohesive zone model formulation provides accurate and robust predictions for fatigue crack propagation, particularly in high stiffness composite interfaces.
• This advancement enhances the simulation capabilities for delamination and debonding in advanced materials.
• The modified model expands the applicability of CZM in fatigue analysis of bonded joints and composites.