Guided wave and damage detection in composite laminates using different fiber optic sensors

Area of Science:

• Materials Science
• Structural Health Monitoring
• Nondestructive Testing

Background:

• Composite laminates are increasingly used in critical structures.
• Effective damage detection is crucial for ensuring structural integrity.
• Fiber optic sensors offer promising solutions for real-time monitoring.

Purpose of the Study:

• To systematically investigate and compare two types of fiber optic sensors for guided wave detection.
• To evaluate their effectiveness in damage detection for carbon fiber reinforced plastic (CFRP) laminates.
• To analyze the characteristics and performance differences between fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors.

Main Methods:

• Construction of guided wave detection systems utilizing both FBG and FOD sensors.
• Propagation of guided waves, generated by a piezoelectric transducer, through a CFRP laminate.
• Acquisition and comparison of guided wave signals by the two sensor types.
• Analysis of signal-to-noise ratio (SNR) and sensitivity to specific wave modes.

Main Results:

• Both FBG and FOD sensors successfully detected guided waves and identified damage in CFRP laminates.
• FOD sensors exhibited a higher SNR compared to FBG sensors due to distinct ultrasonic detection principles.
• FOD sensors demonstrated sensitivity to the damage-induced fundamental shear horizontal (SH(0)) guided wave, which FBG sensors could not detect.

Conclusions:

• Both FBG and FOD sensors are viable for guided wave and damage detection in CFRP laminates.
• FOD sensors offer superior performance in terms of SNR and detection of specific wave modes (SH(0)).
• The omnidirectional nature of FOD sensors contributes to their enhanced detection capabilities compared to the direction-dependent FBG sensors.