Syntactic Foams

Syntactic foams are composite materials synthesized by filling hollow particles (called microballoons) in metals, polymers or ceramics. Presence of hollow particles provides low density to these materials. These materials were developed in early 1960s as buoyancy aid materials for marine applications. However, low density coupled with higher strength, low thermal expansion coefficient, radar transparency led these materials to aerospace and ground transportation vehicle applications.

Tailorability is one of the biggest advantage about these materials. The matrix material can be selected from almost any metal, polymer or ceramic. A wide variety of microballoons are available, which include low cost cenospheres to glass, carbon and polymer microballoons. Glass microballoon-epoxy, glass microballoon—aluminum and cenosphere-aluminum syntactic foams are the most widely studied and used syntactic foams.

It is found that the compressive properties of syntactic foams primarily depend on the properties of microballoons, whereas the tensile properties depend on the matrix material used in their structure. There are two ways of modulating properties of these materials. The first method is to change the volume fraction of microballoon in the syntactic foam structure. The second method is to use microballoons of difference walls.

Among the present applications, some of the common examples are buoyancy risers, boat hulls, and parts of helicopters and airplanes. New applications are coming up in sports industry. Snow skis and Adidas soccer balls are some of the examples.