Reza Akbari - Composites Department, Iran Polymer and Petrochemical Institute, P.O. Box 14975/112, Tehran, Iran.
Mohammad Hosain Beheshty - Composites Department, Iran Polymer and Petrochemical Institute, P.O. Box 14975/112, Tehran, Iran.
Mahdieh Shervin - Composites Department, Iran Polymer and Petrochemical Institute, P.O. Box 14975/112, Tehran, Iran.
Navid Mahnam - Composites Department, Iran Polymer and Petrochemical Institute, P.O. Box 14975/112, Tehran, Iran.

Epoxy resins are highly crosslinked polymers, which have high stiffness, high strength and good solvent resistance. These properties make epoxy an ideal material for structuralapplications, e.g. adhesives, coatings and matrices for fibrereinforced composites [1]. However, when it is cured witharomatic or cycloaliphatic curing agents, the high crosslink density makes these materials inherently brittle, leading to poor resistance to crack propagation [2]. One of the usefulmethods is to incorporate various amounts of flexible amine curing agent with aromatic curing agents into the epoxymatrix. Mechanical properties of diglycidyl ether of bisphenol A (DGEBA) based epoxy resins cured with a mixture of two curing agents have been performed. One of the components ofthe mixed curing agent was dicyandiamide (Dicy) which is widely used as a latent curing agent in heat-cured epoxy resinsfor laminates or prepreg fabrication, coatings, and adhesives, and the other one was a poly(propylene oxide) based amine(Jeffamine D-400). Different epoxy formulations were produced by varying the Jeffamine/Dicy ratios.