NDT of free formed CFRP composites with laser ultrasonics

In recent years the use of carbon fiber reinforced plastics (CFRP) in manufacturing of aircraft and auto cars has increased continually. These materials are of interest because of their excellent mechanical properties like high strength and stiffness at low weight. In consequence of the development of new production processes machine-made CFRP components became more complex in design and shape. The automatic inspection of high quantities of different complex shaped parts is a big challenge for the NDT industry. Especially the examination of free formed composites requires the adaptation of existing equipment or the development of new inspection tools. One new approach for a flexible tool for the investigation of free form CFRP components is laser based ultrasound. This technique has the advantage of being independent from the contour of the component under investigation. The main difference to the well known conventional ultrasonic inspection technique is the substitution of the piezoelectric transducer by two lasers, one for the generation and the other one for the detection of the ultrasound waves. The use of these laser systems enables an inspection without a couplant and with no contact to the component under investigation. In addition this configuration works from greater distances to the objects surface and therefore allows the inspection of structures with difficult access.