Accession Number : AD0778202

Title :   Ultrasonic Measurement of Phase and Group Velocity and Attenuation Using Continuous Wave Transmission Techniques.

Descriptive Note : Final rept. Apr 73-Mar 74,


Personal Author(s) : Lynnworth,Lawrence C. ; Papadakis,Emmanuel P. ; Rea,Warren W.

Report Date : APR 1974

Pagination or Media Count : 80

Abstract : The main purpose of the program was to measure the frequency-dependence of phase velocity, group velocity, and attenuation, for longitudinal and shear waves, in seven different dispersive three-dimensional reinforced woven composites, using continuous wave ultrasonic techniques. A secondary purpose was to determine the errors associated with the usual rf burst zero crossing techniques, when applied to dispersive materials, under the constraints of fixed-path and fixed-frequency. To measure phase velocity V and group velocity U in the composites, we used, for the most part, the fixed-path, variable frequency technique demonstrated by the authors in a previous program. V and U data were thereby obtained over an approximately 50:1 to approximately 100:1 frequency range, up to the low megahertz range, the limit depending on specimen attenuation. The principal limitation of the methods utilized stems from the nonhomogeneous nature of the specimens, and the corresponding difficulty of precisely defining V, U and the attenuation coefficient. (Modified author abstract)

Descriptors :   *Fiber reinforced composites, *Ultrasonic tests, Phase, Velocity, Shear properties, Ultrasonic frequencies, Attenuation

Subject Categories : Laminates and Composite Materials
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE