The main and tail rotors of helicopters are made more and more out of fiber composite materials because of their increased stiffness and strength to weight ratio compared to metallic structures. The earlier helicopter division of MBB, now Eurocopter Germany, has developed the first bearingless main rotor made of glass fiber reinforced materials within the 60īs. By the use of glass fiber reinforced materials the main rotor head of the BO 105 could be made without discrete flap and leadlag hinges. The newer helicopter rotor developments at Eurocopter Deutschland (ECD) have further simplifications of the rotors. The result has been that more and more functions have been integrated into the rotor blade structure, resulting in increasing structural complexity. Such complex structures of fiber composite materials, so e.g. the rotor blades of the EC135, can only be inspected restrictedly with the conventional NDT-methods, like ultrasonics or the conventional X-ray testing. Particularly at thick-wall, monolithic composites the conventional NDT-test procedures fail. The X-ray Computed Tomography (CT) as an imaging test procedure closes this gap. CT is especially suitable for applications involving identification, flaw analysis and structural quantification. This is made possible by the good spatial resolution and the very good resolution of density of the CT-measurements. Subsequently the history of the CT at ECD, the measuring principle of the CT and the necessary technical equipment is described. The paper will be supported by examples, the usage of CT during the development of fiber-reinforced main rotor blades for optimisation the manufacturing techniques. In addition the methodology of the qualification of test procedure for determination the quality of fiber reinforced helicopter rotor blade structures during the manufacturing in series is presented.
Publication Source: International Symposium on Computerized Tomography for Industrial Applications and Image Processing in Radiology March, 15 - 17, 1999 Berlin, Germany. Proceedings BB 67-CD. Publisher:DGZfP - German Society of Non-Destructive Testing