Determination of the orthotropic elastic constants of thin PET filmby an ultrasonic micro-spectrometer

摘要

The elastic constants of a thin polyethylene terephthalate (PET)nfilm, whose thickness was 12 Μm, were determined from the acousticnreflection coefficients. The reflection coefficients were measured by annultrasonic micro-spectrometer (UMSM), and all of the elastic constantsnwere obtained through the fitting of a theory to the dip points of thenmagnitude of the reflection constants where leaky Lamb waves werenexcited. As a result, the film was found to be an orthotropic material,nand the observed elastic constants were consistent with those measurednby tensile tests. Besides, the in-plane shear modulus was found to benmuch larger than the out-of-plane shear moduli. Then, the reflectionncoefficients were calculated using the obtained stiffness matrix. Thencalculated values reproduced not only the dip points but also the changenin magnitude of measured reflection coefficients depending on thenfrequency and the incident angle. These agreements suggest that thenstiffness matrix components were determined accurately