Ultrasonic Signal Attenuation in Syntactic Foams Filled With Rubber Particles

Ultrasonic imaging is a non-destructive evaluation technique, which is used to obtain density profile, phase distribution and three-dimensional profiles of cracks and defects in a material. Although this technique is used for a variety of metals and non-metals, it is difficult to use it for testing of porous materials and foams due to high attenuation of ultrasonic waves in these materials. Syntactic foams are hollow particle filled composites that have recently emerged as attractive material for use in applications requiring low weight, low moisture absorption and high insulation properties. The present paper focuses on determining the attenuation coefficient in syntactic foams and its correlation with porosity distribution. Eight types of foam samples are tested in the study. A combination of four types of microballoons and two types of rubber particles is used. Volume fractions of microballoons and rubber particles are maintained at 0.63 and 0.02, respectively, in all samples. Pulse Echo ultrasonic test method is used and results are compared to determine the effect of constituent particles on the ultrasound signal attenuation. Coefficient of attenuation is observed to increase with decrease in density of foam samples and with decrease in size of rubber particles.Copyright © 2004 by ASME