Effect of microballoon radius ratio on syntactic foam core sandwich composites

Hollow particles, called microballoons, are commonly used in the fabrication of syntactic foams, which are used as core materials in sandwich composites. The present experimental investigation aims at characterizing five different types of syntactic foam core sandwich composites for their edgewise compressive strength. The microballoon volume fraction is maintained at 0.65 in each type of syntactic foams. The five types of microballoons used in the study have the same mean outer diameter of about 40 μm but different wall thickness causing a difference in their densities and strengths. The differences in the compressive strength and modulus of sandwich composites are related to the microballoon radius ratio, which is defined as the ratio of the internal to the external radii of the microballoons. It is observed that the compressive strength and modulus of syntactic foams increase with a decrease in the microballoon radius ratio. The specimen fracture features are also discussed.