Early Damage Detection in Composites during Fabrication and Mechanical Testing.

Area of Science:

• Materials Science
• Mechanical Engineering
• Structural Health Monitoring

Background:

• Composite materials offer high performance but require robust monitoring for reliability.
• Integrated sensing systems can enhance confidence and reduce lifecycle costs of composite structures.
• Understanding in-situ material behavior during fabrication and loading is crucial for composite design.

Purpose of the Study:

• To develop and validate a fully integrated monitoring system for composite materials.
• To investigate resin rheology and strain development during composite fabrication using optical fiber sensors.
• To assess material damage progression under mechanical loading using integrated sensors and acoustic emission.

Main Methods:

• Embedding a distributed optical fiber sensor with three sensing regions through-the-thickness of a composite laminate.
• In-situ monitoring of strain development during the resin infusion process and curing.
• Post-fabrication bonding of piezoelectric wafer active sensors and electrical strain gauges.
• Conducting progressive loading/unloading cycles with four-point bending and acoustic emission analysis.

Main Results:

• Optical fiber sensor data showed good agreement with electrical strain gauges, distinguishing compressive, neutral, and tensile strain regions.
• Acoustic emission detected matrix crack formation, with event amplitudes consistent with literature.
• The Felicity ratio effectively tracked damage progression across loading cycles.

Conclusions:

• The developed integrated monitoring system enables real-time, in-situ assessment of composite behavior from fabrication to end-of-life.
• The methodology provides a comprehensive approach to understanding composite material performance and structural health.
• This integrated sensing approach enhances confidence in composite material applications and supports lifecycle management.