The effects of diatom frustule filling on the quasi-static and high strain rate mechanical behavior of polymer matrices

Abstract

In this study quasi-static tension and quasi-static (1x10-3 and 1x10-1 s-1) and high strain rate (300-600 s-1) compression and quasi-static tensile behavior of diatom frustules-filled, Diatomaceous earth (CD) and Kieslguhr (ND), epoxy matrices were investigated experimentally and microscopically. For comparison, the compression and tensile behavior of the neat epoxy was also determined. Compression results showed that diatom frustules filling increased both modulus and yield strength of the epoxy matrix at quasi-static and high strain rates. ND frustules filled epoxy samples showed a higher strain rate sensitivity compare with CD filled samples. Tensile test results showed that the modulus of filled epoxy increased with increasing frustule content. The frustule filling, however, decreases the tensile failure strains of the epoxy and increased the tensile strength slightly. Microscopic observations on the fracture surfaces and the mounted cross-sections of deformed samples showed that the failure mechanisms were debonding of the frustules-epoxy interface and the fracture of the frustules at quasistatic strain rates while the failure of the filled composite at high strain rate was dominated by the fracture of the matrices. These results confirmed that significant benefits might anticipated from the use of diatom frustules as reinforcements and fillers in polymeric materials. Various methods; acid leaching, thermal shock and ball milling were further applied to process nano size silica powder from frustules. Projectile impact tests indicated that frustule addition increased the ballistic resistance of epoxy matrices. Finally, the strength and modulus of the filled epoxy matrices were predicted using analytical models developed for short fiber composites.