Reaction of carbon fiber sizing and its influence on the interphase region of composites

What might happen with the interphase region of composite if the sizing agent cannot afford the attack of processing temperature and firstly reacted before its combination with the resin, is rarely reported. On the basis of this, herein, effects of sizing reaction on the interphase region of composite were investigated, as well as on the carbon fiber surface properties. It showed that the interfacial shear strength of carbon fiber/epoxy composite was improved after the sizing reaction. The interphase modulus was also increased with a thinner gradient distance. Further analysis indicated that the fiber surface roughness increased, the fiber wettability with the resin lowered, and the chemical reactions between sizing agent and resin reduced after 200°C/2 h treatment on carbon fiber. These results explained the change of the interphase region, which are meaningful for sizing optimization.