Quick google seach .. What some companies are doing with hollow glass micropheres : ‘a syntactic foam product for blast mitigation. “There are millions of microballoons in one square inch of syntactic foam, and at each interface there is an event that dissipates the energy of a blast,” explains Gladysz. He believes this makes syntactic foams ideal for production of moldable protective panels that absorb and dissipate blast energy rather than just transmit and reflect blast effects.

Key applications for antiblast products include lightweight armor plating for military vehicles, lightweight helmet covers, flak jacket inserts and protective composite walls, doors and other structures.’ Link http://www.compositesworld.com/articles/microspheres-fillers-filled-with-possibilities