Accession Number : ADA301918

Title :   Wave Propagation in Anisotropic Medium Due to an Oscillatory Point Source With Application to Unidirectional Composites.

Descriptive Note : Contract rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Williams, James H., Jr. ; Marques, Elizabeth R. ; Lee, Samson S.

PDF Url : ADA301918

Report Date : JUL 1986

Pagination or Media Count : 59

Abstract : The far field displacements in an infinite transversely isotropic elastic medium subjected to an oscillatory concentrated force are derived. The concepts of velocity surface, slowness surface and wave surface are used to describe the geometry of the wave propagation process. It is shown that the decay of the wave amplitudes depends not only on the distance from the source (as in isotropic media) but also depends on the direction of the point of interest from the source. As an example, the displacement field is computed for a laboratory fabricated unidirectional fiberglass epoxy composite. The solution for the displacements is expressed as an amplitude distribution and is presented in polar diagrams. This analysis has potential usefulness in the acoustic emission (AE) and ultrasonic nondestructive evaluation of composite materials. For example, the transient localized disturbances which are generally associated with AE sources can be modeled via this analysis. In which case, knowledge of the displacement field which arrives at a receiving transducer allows inferences regarding the strength and orientation of the source, and consequently perhaps the degree of damage within the composite.

Descriptors :   *FIBER REINFORCED COMPOSITES, *ISOTROPISM, *ELASTIC WAVES, TRANSIENTS, NONDESTRUCTIVE TESTING, DISPLACEMENT, ORIENTATION(DIRECTION), WAVE PROPAGATION, ANISOTROPY, TRANSDUCERS, AMPLITUDE, OSCILLATION, ACOUSTIC EMISSIONS, DIAGRAMS, ULTRASONIC TESTS, UNIDIRECTIONAL.

Subject Categories : Mechanics
      Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE