Non-Destructive Evaluation of Composite Thermal Damage with Agilent’s New Handheld 4300 FTIR

Significance of the Topic

Composite materials widely replace metals in aerospace, automotive, and sporting industries due to their high strength-to-weight ratio. Nondestructive detection of thermal damage is essential to ensure structural integrity, safety, and cost-effective maintenance of composite parts that may exhibit subsurface degradation without visible signs.

Objectives and Overview of the Article

This application note introduces Agilent’s 4300 Handheld FTIR for at-site, nondestructive analysis of thermal exposure in carbon fiber composites. It outlines the development of spectral calibration models, evaluates detector configurations, and validates real-time predictive performance for composite inspection.

Methodology and Used Instrumentation

Diffuse reflectance spectra were acquired using the Agilent 4300 Handheld FTIR equipped with either a DTGS detector or a faster thermoelectrically cooled MCT detector. Composite coupons (unsanded and sanded) were subjected to 375°F–550°F for one hour. Spectra were collected at 8 cm⁻¹ resolution with 64 co-added scans. Partial least squares (PLS) models correlating spectral changes to temperature exposure were implemented in the integrated Microlab software for real-time analysis and quality control.

Main Results and Discussion

Spectral changes in the 1850–1500 cm⁻¹ region served as thermal damage markers: an emerging oxidation carbonyl band near 1722 cm⁻¹ in unsanded samples and reduced absorbance at 1670 cm⁻¹ in sanded samples indicating anaerobic degradation. Calibration models for four composite types achieved high correlation coefficients (R²≥0.92) and low relative errors (<5%). The MCT detector configuration reduced scan times by over 50%, facilitating rapid surface mapping.

Benefits and Practical Applications

The 4300 Handheld FTIR offers:

• Non-destructive, at-site measurement with immediate results.
• Ergonomic, lightweight design for prolonged use.
• Rapid scanning capability, especially with the MCT detector, for extensive area coverage.
• Interchangeable sampling interfaces for diverse composite resins, surface conditions, and contaminants.
• Intuitive software with preprogrammed methods and color-coded thresholds to guide both expert and novice users.

Future Trends and Potential Applications

Expanding chemometric libraries to include new resin systems and hybrid composites will extend the method’s applicability. Integration with automated scanning platforms and in situ monitoring during manufacturing could further enhance efficiency. Continuous health monitoring of critical composite components in service represents a promising direction.

Conclusion

The Agilent 4300 Handheld FTIR is a powerful tool for nondestructive thermal damage assessment in composite materials, combining fast, accurate spectral analysis with user-friendly operation. Its deployment supports informed maintenance, repair, and quality control decisions in the field, addressing the evolving needs of composite-intensive industries.

References

No external references were provided in the original document.