ABSTRACT
CH A P T E R 15 Wave Propagation in Defective Waveguides
In this chapter, a study of the wave propagation characteristics of a mechanical waveguide in the presence of defects is presented. Defects are caused due to various reasons and they differ depending upon the material in which the waveguide is manufactured. For example, the defects in metals are normally in the form of cracks, which are normally caused by high stresses due to high amplitude, dynamic loads. Also, metals are susceptible to corrosion in a highly humid environment, which causes the metal to lose its material especially in the thickness direction causing corrosion pits. In composites, a high level of dynamic stresses can cause delamination of the plies, cracks in the matrix, or even the composite fibers can break. These failures are very different compared to metals. In addition, the laminated composites are prone to moisture absorption leading to reduction in strength and stiffness. Composite structure manufacturing is an involved process that requires precise control of various parameters such as resin flow rate, bagging pressures, etc. It is always difficult to control the composite manufacturing process precisely and this leads to porosity in the manufactured sample. If the level of porosity is over 2.5 percent of a volume fraction of composite, especially for aerospace applications, such samples are not air-worthy. It will be interesting to see the wave characteristics in such defective waveguides. The main objective here is to address only the wave propagation aspects in such defective waveguides and not go over the mechanics behind their analysis.
