Pulse Shaping and Extraction of Information from Ultrasonic Reflections in Composite Materials

Most ultrasonic inspections of materials involve sending elastic waves generated by a transducer through the investigated material, and monitoring either the transmitted waves as appear on the other side of the material, or the reflected waves which return back to the first side. Information about the state of the material is obtained by analyzing the received waves for global acoustic properties as well as local properties that may result from acoustic discontinuities such as defects in the material. Such analysis becomes more difficult when investigating composite materials. These materials have a complex structure, a complex acoustic wave propagation, and are limited to inspection by waves with relatively low frequencies due to high attenuation at high frequencies. All these contribute to more complex waveforms where overlapping of different signals make identification and investigation of discrete events very difficult. Digital signal processing can be used to help in this matter, increase the resolution, and facilitate analysis, as demonstrated here through description of three cases.