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Measurement of sub-surface delaminations in carbon fibre composites using high-speed phase-shifted speckle interferometry and temporal phase unwrapping |
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| Authors: | A Davila P D Ruiz G H Kaufmann J M Huntley |
| Institution: | a Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicester LE11 3TU, UK b Instituto de Física Rosario (CONICET-UNR), Bv. 27 De Febrero 210 bis, S2000EZP, Rosario, Argentina c Departamento de Física, Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, S2000PTB, Rosario, Argentina |
| Abstract: | A high-speed phase-shifted speckle interferometer has been developed recently for studying dynamic events. Speckle interferograms are continuously recorded by a CCD camera operating at 1 kHz with temporal phase shifting carried out by a Pockels cell running at the same frequency. Temporal phase unwrapping through sequences of more than 1000 frames allows the determination of time-varying absolute displacement maps. This paper presents the application of this speckle interferometry system to the detection and measurement of sub-surface delamination defects in carbon fibre specimens. The influence of re-referencing the temporal phase unwrapping algorithm after different time intervals is analysed to reduce the random phase errors produced by speckle decorrelation and vibration. The performance of several phase-shifting algorithms to minimize the influence of the vibration noise caused by the vacuum pump used to load the specimen is also investigated. |
| Keywords: | Speckle interferometry Phase shifting Phase measurement Phase unwrapping Optical metrology |
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