Microballoons (hollow particles) of the same outer radius but with five different inner radius values are used to fabricate five types of syntactic foam slabs. These five types of slabs are used as the core material to fabricate sandwich composites. Three- and four-point bending and short beam shear strength tests are carried out to characterize the flexural behavior of syntactic foam core sandwich composites. The effect of change in microballoon radius ratio (ratio of the inner to the outer radius) on the flexural properties of the sandwich composites is also studied. The results show that in three- and four-point bending tests, the failure is governed by tensile properties of the foam core and the strength is not affected by the microballoon radius ratio. Shear failure takes place in short beam shear tests, which makes the microballoon radius ratio an important factor in determining the strength of the sandwich composite.
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