Some polymers can be toughened by rigid inorganic fillers. In this study, t
he effect of inherent matrix toughness on the fracture of filled thermosets
is systematically investigated using glass heads and epoxies. The tougheni
ng effect of glass beads, i.e. the relative increase of toughness due to th
e incorporation of glass beads, follows an increase in the molecular weight
of epoxides. Inherent matrix toughness is found to increase with the incre
ase of the epoxide molecular weight, Microscopy studies reveal that the siz
es of debonding and micro-shear banding zones are increased as the fracture
toughness of composites increases. Matrix shear yielding is identified as
one of the major energy absorbing mechanisms fur unmodified and modified ep
oxies. (C) 2000 Elsevier Science Ltd. All rights reserved.