Mechanical properties of a new hybrid foam: Closed-cell syntactic foam reinforced with an open-cell aluminum metallic foam

Syntactic foams are light weight particulate composites employed as core materials in sandwich constructions. They are light in weight; possess superior strength and stiffness as well as enhanced thermal insulation, damping and acoustic properties. These characteristics truly make them multifunctional materials. Their low density characteristic made them ideal candidates for many buoyancy aid applications. Currently, due to their multifunctionality, they are widely employed in many structural load bearing constructions in the defense, aerospace and marine sectors. In this study, a systematic step by step procedure of manufacturing, testing and analyzing novel closed-cell syntactic foam reinforced with open-celled aluminum foam was undertaken. Before exploration of this new hybrid foam in various structural, marine and defense installations, an understanding of the mechanical properties is quite necessary. Two types of syntactic foams are manufactured in this study. The first type was fabricated by dispersing glass microballoons, and the second type was obtained by dispersing polymeric microballoons in an epoxy matrix. Two different volume fractions of 30% and 50% were used in manufacturing the syntactic foams. The aluminum foam essentially consist of a 3-D network with a pore size of 20-PPI (20 pores per inch) and average relative density of 7% (the porosity is about 93%). Quasi-static compression and short beam three point bending tests was conducted on syntactic foams without any aluminum reinforcement as the control specimen, and syntactic foams reinforced with the aluminum foams for comparison purposes. The viscoelastic behavior of these materials was also analyzed by performing Dynamic Mechanical Analysis (DMA) tests in tension mode. The current study provides valuable baseline information required for design of such systems and also facilitates better understanding of these hybrid foams as a core material in advanced sandwich structures.