Erstmalig war die Elektrische Messtechnik dieses Jahr mit einem Beitrag beim Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) in Burlington (USA) vom 15. bis 19. Juli 2018 vertreten.
Frau Sarah Johannesmann berichtetete über “Characterization of the linear-acoustic material behavior of fiber-reinforced composites using Lamb waves” (S. Johannesmann, M. Webersen, J. Düchting, L. Claes, B. Henning).
Die Veröffentlichung der Tagungsbandbeiträge steht noch aus.
Although ultrasonic measurement techniques are widely used in non-destructive detection of material defects, the material parameters are still mostly determined destructively using tensile tests. One non-destructive method is the evaluation of guided ultrasonic waves, whose application on fiber-reinforced composites is also challenging due to their high acoustic absorption and anisotropy. In this contribution, Laser-induced Lamb waves are used in the acoustic characterization of plate-shaped specimens. However, pure Lamb modes are independent of the third spatial dimension, so this approach does not yield a complete description of material behavior by evaluation of Lamb waves only. While for some special cases, e.g. isotropy, a complete set of parameters can be derived, this cannot be directly applied to composite materials. Therefore, multiple measurements are performed for different rotations of the sample plate, so that the entire 6x6 elasticity matrix can be determined by combining the individual measurement results. The procedure is exemplarily applied to fiber-reinforced polymer plates with different fiber weave patterns (plain and twill). Although neither mode conversion is considered in the forward model nor shear horizontal modes are evaluated and despite high absorption, the complete elasticity matrix containing both Young’s and shear moduli and Poisson’s ratios can be determined.