Effect of the Resin/Hardener Ratio on Yield, Post-yield,and Fracture Behavior of Nanofilled Epoxies

In this work, the effect of the resin/hardener ratio on the small deformation, yield, post-yield, and fracture behavior of a series of DGEBA-Jeffamine epoxy-clay nanocomposites with a fixed organo-clay content (6 phr), and of the corresponding unfilled resins, was investigated. The mechanical behavior at small deformation was studied by means of uniaxial tensile tests, whereas compression tests were employed to investigate the large (yield and post-yield) deformation levels. The fracture behavior was studied by the application of fracture mechanics testing methods. The results pointed out that small variations in the resin/hardener ratio used for the preparation of the resin can give rise to remarkable differences in the mechanical behavior at large deformation levels and at fracture. These effects were related to the parameters characteristic of the macromolecular architecture of the resins (chain segments flexibility and crosslink density). The results obtained on nanofilled systems showed that the effect of the resin/hardener ratio on the mechanical behavior of the resins is reduced in presence of organoclay particles