Finite Element Modeling for Debonding of FRP-to-Concrete Interfaces Subjected to Mixed-Mode Loading

Area of Science:

• Civil Engineering
• Materials Science
• Computational Mechanics

Background:

• Fiber Reinforced Polymer (FRP) composites are widely used for strengthening concrete structures.
• Understanding the debonding behavior of FRP-to-concrete interfaces under mixed-mode loading is crucial for structural integrity and design.
• Existing models often assume pure mode II interfacial failure, potentially overestimating debonding strength.

Purpose of the Study:

• To investigate the mixed-mode debonding behavior of FRP-to-concrete interfaces using finite element (FE) modeling.
• To evaluate the influence of various interfacial parameters and loading conditions on debonding.
• To provide a more accurate understanding of FRP debonding strength for improved structural design.

Main Methods:

• Finite element (FE) modeling was employed to simulate the debonding behavior.
• A cohesive zone model (CZM) was implemented to represent the FRP-to-concrete interface.
• Orthotropic plane stress elements were utilized for FRP composite simulation, proving superior to beam elements.
• Parametric studies were conducted varying peeling angle and interfacial parameters.

Main Results:

• The mode I component significantly influences debonding failure, even at small peeling angles.
• A transition from mode II-dominated to mode I-dominated failure occurs rapidly with increasing peeling angle (e.g., 4 degrees).
• This transition leads to a dramatic decrease in peeling force, indicating reduced FRP debonding strength.

Conclusions:

• Mixed-mode loading, particularly the mode I component, is critical for FRP-to-concrete interface debonding.
• Current design assumptions of pure mode II interfacial failure may be inadequate.
• Accurate consideration of mixed-mode I/II loading is essential for refining analyses of FRP-strengthened structures and FRP debonding strength design.