Surface Irregularity Factor as a Parameter to Evaluate the Fatigue Damage State of CFRP

Area of Science:

• Materials Science
• Mechanical Engineering
• Non-Destructive Testing

Background:

• Fatigue damage in composite materials like CFRP significantly impacts structural integrity.
• Assessing fatigue damage is crucial for safety and maintenance in aerospace, automotive, and industrial applications.
• Current methods for damage evaluation can be complex or limited in scope.

Purpose of the Study:

• To introduce a novel, non-contact optical technique for evaluating fatigue damage in CFRP structures.
• To correlate surface irregularity measurements with stiffness degradation, a key indicator of fatigue damage.
• To demonstrate the applicability of this technique across different fatigue loading conditions and structures.

Main Methods:

• Development and application of an optical non-contact technique to measure surface irregularity.
• Correlation analysis between the surface irregularity factor and stiffness degradation.
• Application of constant amplitude fatigue loads (CAL) and variable amplitude loads (VAL) to CFRP specimens.
• Utilizing optical profilometry for surface topology assessment.

Main Results:

• The surface irregularity factor, reflecting surface topology, was successfully measured.
• A strong correlation was established between the surface irregularity factor and stiffness degradation.
• The technique proved effective for both CAL and VAL, indicating independence from the load type.
• The method demonstrated applicability for various CFRP structures, including tanks, aircraft components, and automotive parts.

Conclusions:

• The optical measurement of surface irregularity is a viable method for assessing fatigue damage in CFRP.
• This technique offers a simple, field-deployable solution for non-destructive inspection.
• Its independence from loading conditions broadens its applicability across diverse composite structures and industries.