Mechanical and Cryo-Fracture Properties of Core-Shell Clay Filled Epoxy Composites

Abstract

The fracture characteristics and mechanical stability of thermoset composites are of utmost importance in some engineering applications. In this study, novel 3 -aminopropyltriethoxysilane coupled nanoporous organically modified calcites, “core-shell”, clay “SOBM-Ormocal” was used to reinforce phenol-free epoxy matrix. Such particulate n anoporous core-shell fillers are meant to diffuse stress concentrations within their host matrices thereby enhancing shear yielding in composite structures. But, on the contrary, this phenomenon greatly limits yielding and post -yield behaviour in particulate filled thermosets giving interesting fracture characteristics which were clearly evident in electron microscopy images obtained after cryo-fracture of the phenol-free epoxy composite samples. A careful assessment of the matting cracked surfaces presented features of brittle fracture even at very low filler loading, with no discernible stretch fibrils or ribs. Instead, crack pinning, tongues, inclusions, river markings, valleys and plateaus and bifurcations, were evident.