This research will investigate the use of using acoustic signals for quality control in the manufacturing of composites. Recent efforts in acoustic microscopy have been found to be very successful in studying near surface defects in a material. The acoustic material signature of a specimen (obtained using an acoustic microscope) is significantly affected by the surface roughness and near surface defects of a material. However, acoustic microscopes still lack the ability to correctly detect internal cracks or manufacturing defects within a material if these defects are at a depth of a few millimeters or greater from the surface. This is because the operating frequency (100 MHz. - 2 GHz.) of acoustic microscopes is too high for penetration into a material. In this research, an acoustic microscope operating at low frequency (0.1 to 3 MHz.) will be tested in the detection of internal cracks in a composite plate. Several modifications in the microscope design will be investigated to arrive at the best possible design.
