Anomalous fracture behavior in an epoxy-based hybrid composite

In this investigation, core-shell rubber particles and organically modified clay were added to an epoxy resin and the changes in mechanical behavior were studied. As expected, the yield strength of the organoclay-filled epoxies increased modestly with increasing clay content and the yield strength of the rubber-modified compounds decreased with rubber content. Interestingly, the compressive yield strength of epoxy resins containing both rubber particles and organoclay (a.k.a. hybrid nanocomposites) was found to be independent on organoclay content (up to 5 phr). The fracture toughness of organoclay-filled epoxies increased modestly with clay content and, as expected, the increases in fracture toughness were greater for the rubber-modified epoxies. Surprisingly, the addition of nanoclay to the rubber-toughened epoxy resulted in a significant decrease in fracture toughness.