Effect of Density and Volume Fraction of Microballons on Ultrasonic Attenuation Behavior of Syntactic Foams

摘要

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. Several Non Destructive techniques such as Ultrasound are used in the industry to characterize these materials. Though Ultrasonic imaging can be used for a variety of materials, it is difficult to use this technique for porous materials and foams due to high attenuation of ultrasonic waves in air. The present study focuses on the effect of attenuation behavior on the varying density and volume fraction of syntactic foams. Eleven different types of syntactic foams, divided into four types of hollow microballons having different inner diameters, are used in this study. Foam slabs are fabricated by varying the volume fraction of micro balloons from 30% to 50% for each type of microballoon. The Pulse Echo method is used for the ultrasonic imaging of these materials, and thus their ultrasonic attenuation behavior. Coefficient of attenuation is observed to depend upon the open cell porosity and density of the foam sample.