MICROWAVE TECHNIQUE FOR NON-DESTRUCTIVE TESTING OF SOLID PROPELLANT AND COMPOSITE MATERIALS
P. K. Chaturvedi, S. K. Athithan, R. N. Bhattacharya, M. C. Uttam SHAR Centre, ISRO, Sriharikota
Keywords: Microwave ND Testing, Inspection of composite materials, Propellant NDT
ABSTRACT
Microwaves are basically Electro-magnetic waves which can easily pass through a dielectric material whether it is in the form of solid, gas or liquid with certain degree of variation of attenuation in them depending on their dielectric constant. But these waves are opaque to the metallic bodies and rather they are reflected from the metallic surfaces. Based on these properties of the microwaves one can decide its application. This paper deals with application of the microwave technique for the Non- destructive testing of the solid propellant to detect defects like voids, uncured areas, presence of foreign material, etc. Microwaves are very sensitive to a slight change in the dielectric property of a material which considerably influences the transmission of the microwaves through them in terms of attenuation and phase variation. These parameters are easily measurable using suitable microwave receiver system. Materials like solid propellants, resins etc., fall in this category of dielectric materials. During their curing process, dielectric property changes continuously due to chemical reaction of polymerisation. Therefore one can easily differentiate between the cured and uncured material using microwave technique. Also these waves can easily distinguish between gaseous or solid state based on their dielectric property. In this paper, it has been discussed that how a microwave transmission and receiver system has been employed to detect deliberately created defects like holes, filling certain pockets with the uncured propellant and foreign materials in a test article made up of dummy propellant. The microwaves system used for the above ND testing work was planned in the X-band frequency range. The test article was kept on a rotating table in between the transmitting and receiving horn antenna. The microwave transmitted signal through dummy propellant was recorded. The recorded signal pattern indicated peaks corresponding to the defect locations. Minimum defect size detectable, test setup and other technical aspects of this technique are discussed in detail in this paper.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 2, pages 457 - 460 Publisher:Ashgate Publishing Company
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