About Ultrasonic Inspection of Work Pieces and Products from Carbon-Carbon Composite Materials

Abstract

Introduction. Carbon-carbon composite products feature high strength at temperatures up to 3000 C, resistance to aggressive environments, mechanical reliability and relatively low density. Up to now, there are no NDT established procedures for assessing the quality of composite products and their compliance with the technical requirements. Nowadays composites know-how can not guarantee the specified requirements. The paper provides the estimation of the composites ultrasonic testing equipment and procedure. Method. Subjected to studies were samples made a) in compliance with the required production technology, b) to ensure low mechanical properties, c) to ensure wrong frame geometry. An electronic module and transducers were developed so that a shadow method of sample examination in 3 orthogonal planes could be used. Subjected to studies were samples made a) in compliance with the required production technology, b) to ensure low mechanical properties, c) to ensure wrong frame geometry. An electronic module and transducers were developed so that a shadow method of sample examination in 3 orthogonal planes could be used. Results. The paper provides an analysis of relations between ultrasonic wave propagation velocity, signal amplitude, and the spectral maximum. It has been shown that a 200-500 kHz signal is appropriate to test all available samples, whereas a 400-500 kHz signal provides more information on the product and its defects. Defective samples shift the spectrum maximum to lower frequencies which can be used as the product rejection criterion. Possible directions in the further studies to improve the measurement accuracy have been emphasized. Conclusions. The findings show good opening for the carbon-carbon composites acoustic NDT.