Polyester resin based glass fiber reinforced composite panels obtained from a local windmill turbine blade part
manufacturing company are used to evaluate the performance of inter-digital transducer (IDT) surface wave transducers.
Interaction of surface waves with fiberglass layers is addressed in this work. Additionally, artificially created flaws such
as cracks, impact damage and delamination are also studied in terms of amplitude changes in order to attempt to quantify
the size, location and severity of damage in the test panels. As a potential application to the structural health monitoring
(SHM) of windmill turbine blades, the coverage distance within the width of the sound field is estimated to be over 80
cm when a set of IDT sensors consisted of one transmitter and two receivers in a pitch-catch mode.
The paper will give a brief overview on techniques that have been developed or are in progress for high resolution characterization of materials at the Center for Materials Diagnostics, University of Dayton. Acoustic microscopy is used to characterize coating systems and localized defects like corrosion pits. Significantly higher resolution is provided by Ultrasonic force microscopy, which allows the imaging of elastic inhomogenities in materials for example, studying nano-grain structures in copper films and nano precipates in aluminum alloys. Several optical high-resolution techniques have been developed or are in progress. These include interferometric imaging of the response of acoustic MEMS transducers, imaging of acoustic wave structures and early detection of crack initiation. Microellipsometric and NSOM imaging techniques are in development for imaging of surface structures significantly smaller than the optical wavelength. White light interference microscopy is frequently used to characterize surface topography with nanometer resolution for example, to quantify fretting damage or stress fields in front of fractures.
The material being used to construct interconnects in microelectronic circuitry is changing as developers switch from aluminum alloys to copper in order to make increasing smaller circuit wires. The performance of copper interconnects can be adversely affected by electromigration, precipitation formation, and changes in the grain microstructure of the wire. There is a need for characterization methods that can allow examination of the interconnects/wires and their grain structure in the nanometer range. One of the most powerful tools that are routinely used for characterization of nanostructured materials is the Atomic Force Microscope. The combination of AFM with ultrasonics (UFM) allows a near field acoustic microscopic image to be generated. By having the AFM tip detect the ultrasonic signal, the lateral resolution limitation of the acoustic wavelength that occurs in conventional acoustic microscopy can be overcome so that imaging with nanometer resolution is possible. In this paper, we present a qualitative comparison of AFM-UFM images on different forms of copper nanograins from two sources namely, ion beam deposited thin films samples containing polycrystalline sections and the aligned copper grains in the wires of an actual working microelectronic device. Images of the nanometer grain structure will be presented. Explanations for the image differences between samples will be discussed and possible applications are suggested.
The quest for technical advancements is leading scientists to study how devices interact on the nanometer scale. There is a growing need for material characterization techniques, which can image, detect damage/changes, and characterize the material and its engineered structures in the nanometer region. One of the most powerful tools that are routinely used for characterization of nanostructured materials is Atomic Force Microscopy. The Atomic Force Microscope (AFM) provides a 3 dimensional surface topographic image of a sample. When imaging a sample's surface, a 10-micron or smaller area maybe fairly flat so that the AFM image provides very little detail and contrast even though the overall sample surface is quite rough. Ultrasonic Force Microscopy (UFM) has been developed in order to improve the image contrast on flat areas of interest where the AFM topography images are limited in contrast. The combination of AFM-UFM allows a near field acoustic microscopic image to be generated. The AFM tip is used to detect the ultrasonic waves and overcomes the lateral resolution limit of the acoustic wavelength that occurs in acoustic microscopy. By using the elastic changes under the AFM tip, an image of much greater detail than the AFM topography can be generated. Nondestructive evaluation and material characterization on ceramic and copper applications in which the addition of UFM has greatly improved upon the AFM images is presented.