Prof. Dr. Habil. Rymantas Kažys rymantas.kazys@ktu.lt Prof. K. Baršauskas Ultrasound Research Institute
Ultrasonic non Destructive Testing of Composite Structures Composites are the materials of the XXI century. They are being used in such important areas as aviation and space industry, energy generation systems, materials science etc. Composites are made from several components. Most common composites are glass or carbon fibres glued together. Such materials have few essential advantages compared to metals. Constructions made from them are lighter and at the same time even stronger than made using metal. Secondly, composite structures are manufactured by gluing fibres layer by layer. So, it enables to create structures, in general, of any geometrical shape. Moreover it can be created as a single piece. Insertion of the layers of honeycomb structures, foam or balsa wood into the composite enables to create extremely light and strong structures. Most widely composite materials are used in aerospace industry, but in recent years they are used for manufacturing of wind turbine blades, aerodynamic bodies of racing cars, busses, trains, yachts.
Ensuring Safety Main disadvantage of composite structures is that in most cases they are manufactured manually. Taking into account complexity and non-uniformity of structure it can lead to presence of defects such as delamination, lack of glue and brake of fibres. Thus due to safety reasons such composite structures need to be tested. However an inspection of so complex structures is also not a simple task. One of main techniques which can be exploited for non-destructive testing of composite materials is based on applications of ultrasonic waves.
Methods and Technologies Parameters of propagating ultrasonic waves depend on the elastic properties of the material, the dimensions of the object or the presence of nonuniformities therein. Received ultrasonic signals contain information about the condition of object or material. In view of that, ultrasonic waves are widely used for detection of defects in various objects, the exploitation reliability whereof is essential. Such technique is called Ultrasonic
Non-Destructive Testing (UT NDT). However one of most important parameters of ultrasonic waves related to the inspection of composite structures is how they are absorbed and scattered by the material. Higher frequency waves allow better accuracy of the measurements. However it also brings about bigger losses. For example, the waves generated at 3-5 MHz penetrate into composite material only several millimeters. Kaunas University of Technology
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