Fracture toughness of spherical silica-filled epoxy adhesives

Crack propagation in epoxy adhesives filled with spherical silica was inves tigated using double cantilever beam (DCB) specimens. In particular, to cla rify the effect of particle size and particle/matrix adhesion upon the frac ture toughness, silica particles were prepared with mean particle sizes in the range of 6-30 mum, where the particles were treated with gamma -aminopr opyl methyldiethoxysilane and hexamethyl disilazane. The former and latter treatments demonstrated well- and poorly-bonded interfaces between the part icle and matrix, respectively. The experimental results showed that the fra cture toughness of DCB specimens increases with particle size and with inte rfacial strength of silica/matrix depending on the particle content. The be havior has been interpreted in terms of crack pinning and crack blunting. ( C) 2001 Elsevier Science Ltd. All rights reserved.