Experimental determination of fracture toughness of epoxy toughened with nano-block copolymers

Abstract

A lack of resistance to crack growth and initiation limits the application of epoxy in fields requiring high fracture toughness. Means to improve the fracture toughness of epoxy are commonly achieved through the addition of a secondary phase. The study of increasing levels of Nanostrength® M52N nano-block copolymers with a bisphenol A epoxy resin has been investigated due to low agglomeration of the nanophase, and retention of mechanical and thermal properties signature to epoxy. Mode I fracture toughness has been determined using double cantilever beam testing. A modified simple beam theory for brittle, linear elastic behaviour, has accounted for bond line properties and non-symmetrical crack propagation of the adherend. Experimental investigation has shown improvements of stress intensity factor for Mode I failure, KIc, of 173% for 10% volume fracture nanophase.