Specific properties and fracture toughness of syntactic foam: Effect of foam microstructures

Studies were performed on the specific strength, moduli and fracture toughness of varied microstructures of syntactic foam. The different microstructures were created by using three different types of microspheres, namely 3M Scotchlite™ K15 and K46 glass bubbles, and Phenoset BJO-093 hollow phenolic microspheres, and by changing the volume fractions of microspheres from 0 to 50 vol%. Tension, compression, flexural and fracture tests were performed. Results showed that the tensile and flexural strengths decreased with increasing filler content. The behavior of the tensile and flexural strength was not affected by the component microspheres. Interestingly, the tensile and flexural moduli showed different trends for each type of microspheres with increasing filler content. Results of the compression tests revealed superior behavior of the high density microspheres. The specific fracture toughness data yielded maximum values at 30 vol% for each type of microspheres investigated. Scanning electron microscope studies were performed to determine the failure mode for each loading condition.