Inorganic particle toughening II: toughening mechanisms of glass bead filled epoxies

Based on the previously established knowledge about the micro-mechanical de formations occurring during the fracture of glass bead filled epoxies, the major energy dissipation mechanisms are investigated. Correlation studies b etween the fracture toughness of composites and the size of micro-mechanica l deformation zones (or areal density of deformation) are used to assess th e contributions of the deformations to toughening. Among the deformations f ound in the fracture of glass bead filled epoxies, i.e. micro-shear banding , debonding of glass beads/diffuse matrix shear yielding, and step formatio n, micro-shear banding is established as the major and most effective tough ening mechanism. In terms of this mechanism, the negligible effect of surfa ce treatments of glass beads on the fracture toughness of glass bead/thermo set composites can be explained successfully This mechanism is expected to give more detailed and fundamental understanding of inorganic particle toug hening than the crack front bowing mechanism. (C) 2000 Published by Elsevie r Science Ltd.