| A basic physical explanation, a model, and comments on NDE application of the acousto-ultrasonic method for composite materials are presented. The basis of this work is a set of experiments where a sending and a receiving piezoelectric transducer were both oriented normal to the surface, at different points, on aluminum plates, various composite plates, and a tapered aluminum plate.; Chapter one introduces the purpose and basic idea of the dissertation, while supporting its need. Also, general comments on the AU method are offered. The second chapter offers a literature review of areas pertinent to the dissertation, such as composite materials, wave propagation, ultrasonics, and the AU method. Special emphasis is given to theory which is used later on and past experimental results that are important to the physical understanding of the AU method. The third chapter describes the experimental set-up, procedure, and the ensuing analysis. In the fourth chapter, the experimental results are presented in both a quantitative and qualitative manner. Chapter five furnishes a physical understanding of experimental results based on elasticity solutions, Lamb wave theory, and through-the-thickness-transverse-resonance (TTTR). Computer results are presented for sake of comparison. The sixth chapter discusses modeling and applications of the AU method for composite materials and the seventh chapter states general conclusions.; The unique offering of this work is the physical model of the AU method for composite materials, something which has been much needed and sorely lacking. This physical understanding is possible due to the extensive set of experimental measurements, also reported in this dissertation. |
