On the accuracy of monitoring inter-fibre fractures in composites using passive infrared thermography extended by microscopic analysis

ABSTRACT

This work deals with the accuracy of a non-destructive testing methodology to monitor the evolution of inter-fibre fractures in $[{90}_3/0_2{]}_s$ cross-ply carbon fibre-reinforced polymer laminates. Specimens are subjected to a continuous 3-point bending test. The locations of local energy releases corresponding to inter-fibre fractures are recorded during the experiment using passive infrared thermography. They are correlated to reference positions from an optical microscopic analysis in a post-processing step. The absolute difference between both positions is a measure for the accuracy of the passive infrared thermography. A correction function for the infrared data as well as criteria for the correlation and test execution are derived. The correlation allows the introduced methodology for low error localisation of inter-fibre fractures providing temporal and spatial information. The resulting temporal error is in the range of milliseconds, the spatial error in the range of microns.

KEYWORDS:

• Carbon fibre-reinforced polymer
• damage evolution
• inter-fibre fracture
• passive infrared thermography
• 3-point bending test

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft under grant number 3933868053. Sincere appreciation to Hamburg University of Technology/Institute of Polymer Composites for the provision of the CFRP substrates.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft [3933868053].