Acousto-Ultrasonic Wave Propagation in Composite Laminates
In the acousto-ultrasonic technique, a wave is injected onto the surface at one location and the displacement normal to the same surface is measured at another location. Thus, understanding the propagation characteristics of the wave is essential for successful application of the technique. The main objective of the present investigation is to identify through analysis-experiment correlation how the AU wave propagates through composite laminates.
Lamb wave speeds were calculated in the low frequency region for a unidirectional graphite/ epoxy laminate. For wave propagation in off-axis directions transverse displacement was assumed zero. An experimental verification was carried out by measuring the wave speeds on the upper and lower surfaces of the specimen. The changes of the wave velocity and attenuation with frequency were monitored. Fourier spectra of the received signal were obtained using a wave analyzer to study the dispersion.
It has been found that the dominant AU waves produced experimentally were Lamb waves. The wave velocity changed with the fiber direction in the predicted manner. The maximum attenuation was obtained in the 22.5° fiber direction while the minimum attenuation was observed parallel to the fibers.
KeywordsWave Velocity Acoustic Emission Attenuation Coefficient Peak Amplitude Fiber Orientation
Unable to display preview. Download preview PDF.
- 3.H. F. Pollard, “Sound Waves in Solids”, Pion Limited, London (1977).Google Scholar
- 4.I. A. Viktrove, “Rayleigh and Lamb Wave,” Plenum Press, New York (1967).Google Scholar
- 5.J. H. Hemann and G. Y. Baaklini, “The Effect of Stress on Ultrasonic Pulses in Fiber Reinforced Composites, NASA CR-3724,” NASA, Cleveland (1983).Google Scholar
- 7.L. J. Bond and N. Saffari, Crack Characterization in Turbine Disks, in: “Review of Progress in Quantitative Nondestructive Evaluation, Vol. 3A,” D. O. Thompson and D. E. Chimenti, eds., Plenum Press, New York (1984).Google Scholar
- 8.A. Fahr, S. Johar, and M. K. Murthy, Surface Acoustic Wave Studies of Surface Cracks, in: “Review of Progress in Quantitative Nondestructive Evaluation, Vol. 3A,” D. O. Thompson and D. E. Chimenti, eds., Plenum Press, New York (1984).Google Scholar
- 10.F. C. Moon, Wave Propagation and Impact in Composite Materials, in: “Mechanics of Composite Materials, Vol. 7,” C. C. Chamis, ed., New York (1974).Google Scholar
- 15.J. D. Achenbach, Waves and Vibration in Composites, in: “Mechanics of Composite Materials, Vol. 2,” G. P. Sendeckyji, ed., Academic Press, New York (1974).Google Scholar
- 17.S. Serabian, “Implication of the Attenuation-Produced Pulse Distortion Upon the Ultrasonic Method of Nondestructive Testing,” Matl Eval. 26:173 (1968).Google Scholar
- 19.R. M. Jones, “Mechanics of Composite Materials,” Scripta Book Company, Washington, DC (1975).Google Scholar