Numerical Analysis on Optimal Adhesive Thickness in CFRP Single-Lap Joints Considering Material Properties

Area of Science:

• Materials Science
• Mechanical Engineering
• Structural Analysis

Background:

• Assessing adhesively bonded joint strength is critical for structural reliability.
• Size-dependent effects present challenges in consistent strength evaluation.
• Carbon fiber reinforced plastics (CFRP) are increasingly used in structural applications.

Purpose of the Study:

• To investigate the impact of adhesive thickness on the strength of Single Lap Shear (SLS) joints.
• To determine the optimal adhesive thickness range for maximizing joint strength.
• To analyze the local stress state at fracture initiation in CFRP joints.

Main Methods:

• Finite element simulations of Single Lap Shear (SLS) tests were performed.
• Analysis included unidirectional and quasi-isotropic CFRP adherends.
• Three adhesives (polyphenylene sulfide, polyether ether ketone, epoxy) and thicknesses from 0.1 mm to 0.5 mm were evaluated.

Main Results:

• Optimal adhesive thickness for maximizing joint strength was found to be between 0.1 mm and 0.3 mm.
• Adhesive layers that were too thin or too thick resulted in reduced joint performance.
• Simulation results demonstrated alignment with experimental trends.

Conclusions:

• Adhesive thickness significantly influences the strength of CFRP bonded joints.
• A specific thickness range (0.1-0.3 mm) is recommended for optimal joint performance.
• Findings support the development of precise design guidelines for polymer-based structural joints.