Syntactic foams:

Syntactic foams are particulate composite materials having hollow particle, called cenospheres, in some kind of matrix material, which can be polymer or metal. Syntactic foams are used in various applications owing to their high strength to weight ratio and highly tailorable properties.

The syntactic foam design tool is intended for users to design syntactic foams for material properties, namely, mechanical, electrical and thermal. User can obtain values like volume fraction and radius ratio of cenospheres required for the foam to exhibit a specific property. The design process is based on various numerical models developed to approximate syntactic foam material properties. These methods have been published in distinguished journals and have been referred to by various researchers.

The current applications and many future possibilities for syntactic foams are discussed in the following publication:
Gupta, N., Zeltmann, S. E., Shunmugasamy, V. C. and Pinisetty, D., Applications of polymer matrix syntactic foams. JOM, 2014, 66(2): p. 245-254. (PDF Download)