Unstable Delamination Growth in Stiffened Composite Panels Under Cyclic Loading Conditions

Area of Science:

• Composite Materials Science
• Aerospace Engineering
• Structural Integrity Analysis

Background:

• Foreign object impacts (FOIs) critically damage aeronautical composite structures.
• Delamination, an undetectable damage, is exacerbated by cyclic loading, reducing structural capacity and potentially causing collapse.
• Predicting unstable delamination growth under fatigue is challenging for traditional non-linear finite element methods (FEMs) due to convergence issues.

Purpose of the Study:

• To present an efficient alternative methodology for analyzing delamination propagation under cyclic loading in composite structures.
• To develop a model capable of accurately accounting for the decrease in load-carrying capacity during delamination growth.
• To validate the methodology's effectiveness in predicting delamination behavior in aeronautical components.

Main Methods:

• Implementation of the Paris law approach within the ANSYS FEM code.
• Utilization of an enhanced virtual crack closure technique (VCCT)-based method.
• Application of non-linear static analyses with alternating force and displacement-controlled FEM simulations.

Main Results:

• The proposed methodology efficiently analyzes delamination propagation under cyclic loading.
• The model accurately predicts the decrease in load-carrying capacity as delamination grows.
• Successful prediction of delamination growth in stiffened aeronautical panels subjected to cyclic compression loading.

Conclusions:

• The developed methodology offers an efficient and accurate alternative for simulating delamination growth in composite structures.
• This approach enhances the prediction of structural integrity under fatigue loading, crucial for aeronautical applications.
• The study demonstrates the capability of non-linear static analyses to overcome convergence challenges in dynamic delamination simulation.