DIC Analysis in High-Speed Tensile Test of CFRP

Importance of the Topic

Carbon fiber reinforced plastics (CFRP) combine high specific strength and low weight, making them essential in aerospace, automotive and other industries. Their brittle fracture behavior demands high-speed imaging and accurate strain measurement to understand crack initiation and propagation.

Study Objectives and Overview

This study demonstrates the application of digital image correlation (DIC) in high-speed tensile testing of CFRP, leveraging a newly developed high-resolution camera (Hyper Vision HPV-X3) and a high-speed tensile testing machine (HITS-TX). A comparative assessment against a conventional system (HPV-X2) evaluates improvements in DIC performance.

Methodology and Instrumentation Used

Specimen preparation involved adhering aluminum foil to the specimen back for electrical triggering upon fracture. A random speckle pattern on the front surface enabled DIC measurement. Key equipment included:

• Hyper Vision HPV-X3 high-speed camera (20 Mfps, 300 kpx resolution)
• Hyper Vision HPV-X2 camera (10 Mfps, 100 kpx resolution)
• HITS-TX tensile testing machine (up to 20 m/s crosshead speed)
• 10 kN load cell, 105 mm macro lens, strobe lighting, high-speed grips
• VIC-2D DIC analysis software

Test conditions featured a 10 m/s loading speed on a quasi-isotropic CFRP laminate.

Main Results and Discussion

DIC analysis of high-speed images revealed early strain localization in a 45° orientation, with the HPV-X3 capturing finer details of strain concentration immediately before crack initiation. Enhanced resolution (3× higher) and increased frame rate (2× faster) of the HPV-X3 yielded sharper strain maps and more precise temporal tracking of fracture events compared to the HPV-X2.

Benefits and Practical Applications of the Method

• Improved visualization of initiation and propagation of brittle fractures
• Higher spatial and temporal resolution enhances DIC accuracy
• Applicable to the development and quality assurance of composite materials
• Enables detailed failure analysis under dynamic loading conditions

Future Trends and Potential Applications

Advancements may include further increases in camera speed and resolution, integration with real-time data processing and AI-based pattern recognition, expansion to three-dimensional DIC using multi-camera setups, and in-line monitoring in manufacturing processes for composites and other brittle materials.

Conclusion

The combination of the Hyper Vision HPV-X3 camera and HITS-TX tensile testing machine significantly improves the capability to observe and quantify dynamic fracture processes in CFRP via DIC. This system provides a robust tool for research and industrial evaluation of composite materials.