Accession Number : ADA300676

Title :   Input-Output Characterization of Fiber Composites by SH Waves.

Descriptive Note : Final contractor rept.

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE

Personal Author(s) : Renneisen, John D. ; Williams, James H., Jr

PDF Url : ADA300676

Report Date : JUN 1988

Pagination or Media Count : 42

Abstract : Input-output characterization of fiber composites is studied theoretically by tracing SH waves in the media. A fiberglass epoxy composite is modeled as a homogeneous transversely isotropic continuum plate. The reflection of a SH wave at a stress-free plane boundary in a semi-infinite transversely isotropic medium is considered first. It is found that an incident SH wave reflects only a similar SH wave back into the medium. It is also established that the angle of reflection of the reflected wave is equal to the angle of incidence of the incident wave. The phase velocity of the SH waves and the delay time of the SH waves in reaching the receiving transducer are computed as functions of a reflection index, defined as the number of reflections of the SH waves from the bottom face of the continuum plate. The directivity function corresponding to the shear stress associated with the SH waves in the continuum plate is also derived as a function of the reflection index. A theoretical output voltage from the receiving transducer is calculated for a tone burst (a periodic input voltage of finite duration). The output voltage is shown for tone bursts of duration 60 microns and center frequencies 0.75, 1.00, and 1.25 MHz. The study enhances the quantitative and qualitative understanding of the nondestructive evaluation (NDE) of fiber composites which can be modeled as transversely isotropic media. (MM)

Descriptors :   *FIBER REINFORCED COMPOSITES, *EPOXY COMPOSITES, VELOCITY, FIBERGLASS, EQUATIONS OF MOTION, NONDESTRUCTIVE TESTING, DISPLACEMENT, ELASTIC PROPERTIES, EIGENVALUES, VOLTAGE, REFLECTION, BOUNDARY VALUE PROBLEMS, TRANSDUCERS, ANGLE OF INCIDENCE, TRAVELING WAVES, PARTICLE TRAJECTORIES, CARTESIAN COORDINATES.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE