Imaging Surface Displacements of Piezoelectric Composites
Studies over the last ten years have shown that composite piezoelectrics can have a significant advantage over monolithic materials for a number of applications, especially in transducers used in medical imaging. In conventional ceramics the Poisson effect lowers the thickness mode displacement that can occur in wide specimens at high frequencies. This effect is sometimes referred to as self pinning. In one specific type of composite (type 1–3) the proper incorporation of an array of rods made from a piezoelectric ceramic such as PZT in an inactive matrix such as epoxy will form a composite piezoelectric with much lower self pinning than occurs in a monolithic ceramic. For medical applications composite transducer materials may consist of rods as small as 100 microns across and separated by about 25 microns. For lower frequency applications, the rods may be as large as 1.0 mm and be separated by 4.0 mm or more. Characteristics of piezoelectric composite materials and the conventions used in naming them are described in a review article by Smith .
KeywordsDisplacement Field Thermal Displacement Standing Wave Pattern Equivalent Noise Level Proper Incorporation
Unable to display preview. Download preview PDF.
- 1.W. A. Smith, “New Opportunities in Ultrasonic Transducers Emerging from Innovations in Piezoelectric Materials,” 1992 International Symposium, New Development in Ultrasonic Transducers and Transducer Systems, 21–22 July, 1992.Google Scholar
- 2.T. R. Gururaja, W. A. Schultz, L. E. Cross, B. A. Auld, Y. A. Shui, and Y. Wang, “Piezoelectroc Composite Materials for Ultrasonic Applications.Part I: Resonant Modes of Vibration of PZT Rod-Polymer Composites,” IEEE Transactions on Sonics and Ultrasonics, p 481, Vol SU-32, No4 (1985).Google Scholar
- 3.W. R. Scott, M. J. Ryan, D. M. Granata and N. Sottos, “Nondestructive Evaluation and Characterization of Composite Materials: Microinterferometry”, Proceedings of the Navy IR/IED Symposium, Johns Hopkins Applied Research Laboratory, (21 July 1988 ).Google Scholar
- 4.N.R. Sottos, M.J. Ryan, and W.R. Scott, Naval Air Development Center, Warminster, PA 18974, “Measurement of Local Thermal Displacements at the Fiber/Matrix Interface Using Micro-Interferometry”; presented, Review of Progress in Quantitative Nondestructive Evaluation, USCD, Aug 1990; Submitted for Publication, Progress in Quantitative Nondestructive Evaluation, Vol.9, Plenum, (1991).Google Scholar
- 5.Martin J. Ryan, W. R. Scott, Nancy Sottos, “Scanning Heterodyne Micro- interferometer for High Resolution Contour Mapping,” presented, Review of Progress in Quantitative Nondestructive Evaluation, USCD, Aug 1990; Submitted for Publication, Progress in Quantitative Nondestructive Evaluation, Vol.9, Plenum, (1991).Google Scholar
- 6.N. R. Sotos, W. R. Scott, and R. L. Mc Cullough, “Micro-Interferometry of Thermal Displacements at Fiber/Matrix Interfaces,” Experimental Mechanics, V31, #2, 98–103, June 1991.Google Scholar
- 7.Clyde Oakley, “Analysis and Development of Piezoelectric Composites for Medical Applications,” PhD Thesis, The Pennsylvania State University, 1991.Google Scholar