抄録
Rubber-modified epoxy resin is widely employed as a base for adhesive compositions and as a matrix material for glass and carbon-fiber composites. A damage zone is generated around a crack tip before fracture. This damage zone is caused by the deformation of rubber particles dispersed in the matrix resin. Its size is closely correlated with the fracture toughness of the resin. In this study, we investigate the deformation of rubber particles inside a damage zone and the relation between the fracture toughness and the size of a damage zone around a crack tip, that is, the length, width, and area under mixed mode condition. The fracture toughness (KIC) and the fracture energy (GC) are measured using an end notched circle type (ENC) specimens. The damage zones around crack tips of damaged specimens are observed by a polarization microscope. As a result, the fracture energy (GC) of rubber-modified epoxy resin has close relationship with the area of damage zone. The rubber particles are deformed elliptically due to the difference of the components of principal stress in the specimen whose load angle is 30 degree.
