Accession Number : ADA300528

Title :   Acousto-Ultrasonic Input-Output Characterization of Unidirectional Fiber Composite Plate by SV Waves.

Descriptive Note : Final contract rept.,

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

Personal Author(s) : Liao, Peter ; Williams, James H., Jr

PDF Url : ADA300528

Report Date : JUN 1988

Pagination or Media Count : 90

Abstract : This study increases the quantitative understanding of acousto-ultrasonic nondestructive evaluation (NDE) parameters such as the stress wave factor (SWF) and wave propagation in fiber reinforced polymeric, ceramic or metallic composites, which can be modelled as transversely isotropic media. A unidirectional fiberglass epoxy composite specimen is modelled as a homogeneous transversely isotropic continuum plate medium. Acousto-ultrasonic noncontact input-output characterization is studied theoretically with a transmitting and a receiving transducer located on the same face of the plate. The single reflection problem for an incident SV wave at a plane boundary in transversely isotropic medium is analyzed. It is found that an obliquely incident SV wave results in a reflected SV wave and a reflected P wave for an angle of incidence of the incident SV wave less than the critical angle. When the angle of incidence of an incident SV wave is equal to or greater than the critical angle, there exists only an SV wave in the medium as the reflected P wave degenerates into a surface wave travelling parallel to the plane boundary. The amplitude ratio of the reflected SV wave is found to be minus one when the angle of incidence is equal to or greater than the critical angle. It is found that the directional dependence of the phase velocity of the SV wave propagating in the transversely isotropic medium has a significant effect on the delay time, as opposed to the directional independence of the phase velocity of a shear wave propagating in an isotropic medium. The displacements associated with the SV wave in the plate and which may be detected by the noncontact receiving transducer are approximated by an asymptotic solution for an infinite transversely isotropic medium subjected to a harmonic point load.

Descriptors :   *NONDESTRUCTIVE TESTING, *COMPOSITE MATERIALS, *STRESS WAVES, SHEAR PROPERTIES, RATIOS, SURFACE WAVES, LOADS(FORCES), DISPLACEMENT, FIBER REINFORCED COMPOSITES, HARMONICS, COMPOSITE STRUCTURES, REFLECTION, BOUNDARIES, CERAMIC MATERIALS, ULTRASONICS, WAVE PROPAGATION, PLATES, ISOTROPISM, ASYMPTOTIC SERIES, ANGLE OF INCIDENCE, POINT THEOREM, ELECTROACOUSTIC TRANSDUCERS, ELASTIC WAVES, DIRECTIONAL, UNIDIRECTIONAL, FACEPLATES, PHASE VELOCITY.

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

Distribution Statement : APPROVED FOR PUBLIC RELEASE