Abstract
A model composite method was proposed to evaluate the interfacial fracture toughness between fiber and matrix, where the resin fracture is not involved. In the composite, two glass fibers from 10 to 15μm in diameter were bonded by resin. In the present study, two kinds of surface treatments were conducted for the glass fibers. One was the acrylic-silane coupling, and the other one was the 3-methacryloxy-propyl tri-ethoxysilane coupling. The interfacial strength is low for the former and it is high for the latter. Two kinds of resins were also employed for the matrix, one was vinylester resin, and the other one was unsaturated polyester resin. The former is ductile and the latter is brittle. In-situ observation testing system was developed for Mode I fracture toughness tests of the model composite, where the resolution of applied force was about 0.01 mN. For the model composites consisted of either the low interfacial strength fiber and the ductile resin or the high interfacial strength fiber and the brittle resin, the crack propagation was unstable, and the interfacial fracture toughness could be evaluated. On the other hand, ductile fracture occurred in the resin and the interfacial fracture was not evaluated for the model composite consisted of the high interfacial strength fiber and the ductile resin.
