Wave Propagation on Thin Lightweight Structures

One of the goals of this research is to investigate the use of controlled stress-wave propagation for structural healing. The paper begins with a review of the recent literature in the area of self-healing materials with a view to understanding possible use of acoustic energy to accelerate the healing process. Using a simple 1-dimensional propagation example, the paper investigates time reversed acoustics as a method to deliver focused acoustic energy at the defect. Also reported are results form wave propagation experiments that were conducted on synthetic membranes with and without different types of defects such as scratches, slices, holes, and cracks. The analytical work shows that energy in a series of wave pulses scattered by a defect can be captured using transducers and focused at the site of the defect. Since both pressure and temperature affect the healing process, further theoretical and experimental investigations are needed in order to provide an understanding of the effect of acoustic focusing on the rate and nature of healing. HE current aim of this study of wave propagation across thin lightweight structures is to observe the behavior of wave feedback in real time. As the waves travel across the membrane and the frequency response is observed, one may deduce the behavior of not only the wave, but also the membrane. In this study, wave propagation across a synthetic collagen-like membrane is studied. The wave, phase, and frequency response patterns are studied with the goal of detecting an imperfection in the surface. Among the defects considered are scratches, cracks, slices, and holes. A survey of the state of the art was conducted to obtain a realistic impression of current wave studies and membrane healing projects. In theory, if the energy from the waves could be harnessed, it could also be reversed and used to create concentrated constructive or destructive interference focused at the defect. In an ideal system, the acoustic energy harnessed would induce healing of the membrane. To illustrate the healing process, it was animated using the Java Swing programming language.