Laser generated ultrasound: efficiency and damage thresholds in carbon fibre reinforced composites

Citation
C. Edwards et al., Laser generated ultrasound: efficiency and damage thresholds in carbon fibre reinforced composites, IEE P-SCI M, 148(4), 2001, pp. 139-142
Citations number
19
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEE PROCEEDINGS-SCIENCE MEASUREMENT AND TECHNOLOGY
ISSN journal
13502344 → ACNP
Volume
148
Issue
4
Year of publication
2001
Pages
139 - 142
Database
ISI
SICI code
1350-2344(200107)148:4<139:LGUEAD>2.0.ZU;2-U
Abstract
Laser techniques are beginning to be used for non-contact ultrasonic inspec tion of carbon fibre reinforced composites in industry. The ultrasound is n ormally generated with a high-power pulsed laser and is detected with a las er interferometer. Other non-contact detection methods can also be used, su ch as simpler laser beam deflection techniques and air coupled transducers. The authors compare the generation efficiency and damage thresholds of a f undamental Nd:YAG laser (1.06 mum), and a TEA CO, laser (10.6 mum) which is normally preferred for carbon-fibre reinforced composites). A Nd:YAG laser with an optical parametric oscillator (OPO) tunable up to 4 mum is also ex amined. The laser energy is absorbed within the optical absorption depth; t he temperature rise is affected by the wavelength and laser pulse duration. It is essential to remain in the thermoelastic regime in order not to dama ge the material. A modified Michelson interferometer is used to detect the absolute displacement of the ultrasound. Optical beam deflection techniques and air-coupled transducers are also evaluated as detectors.