Advanced interfacial properties of glass fiber/dopamine-epoxy composites using a microdroplet pull-out test and acoustic emission

The evaluation of interfacial properties between fiber and epoxy resin is very important. An advanced microdroplet pull-out test was introduced to quantitatively evaluate the interfacial adhesion. To improve the interfacial property, dopamine was added in the epoxy resin whereas grease treatment was applied to the glass fiber to reduce the interfacial property. The pull-out forces of microdroplets as well as acoustic emission energy were measured by establishing a relationship between the adhesive force and acoustic emission energy per embedded length. Microdroplet fatigue tests were performed on microdroplets with the same embedded lengths. To observe the effect of interfacial properties, tensile specimens of milled glass fiber-reinforced epoxy composite were manufactured and tensile tests were conducted. During this tensile testing, the stress distribution was determined using polarized optical light. The results indicated that the dopamine conditions produced the highest degree of curing of the epoxy resin resulted in improved mechanical properties and interfacial shear strength. In addition, the studies also demonstrated that the debonding and fracture forces of the microdroplets were proportional to the acoustic emission energy accompanying fracture of specimens during microdroplet pull-out test with the associated acoustic emission test.