Interfacial evaluation of carbon frinforced nano-composites using electrical resistance measurement with wetting tests

Abstract

The use of carbon fiber reinforced plastic (CFRP) is rapidly increasing in aerospace and automobile applications. The fiber-matrix interface has been found to be important for high strength in composites. Methods to improve interfacial property of composites include: the addition of coupling agents, surface modifications, chemical reaction control and use of nanofillers for reinforcement. During mechanical loading the shape of carbon fibers is altered with a concomitant change in electrical resistance (ER). Carbon fibers are used as sensing elements in CFRP due to their electrical conductivity for damage sensing. The movement of carbon fiber could be detected by ER measurement. During loading, the extent of contact between carbon fibers in a CF tow is altered, and the ER changes from its initial value. Interfacial properties of carbon fiber/polymer composites were evaluated by ER measurements. During the wetting process of CF tows by the polymer resins, the change in ER was analyzed. The ER change was associated with different wetting conditions, and the interfacial properties were predicted by ER measurements. CF tow/epoxy exhibited the poorest carbon tow wettability, the smallest change in ER and the poorest IFSS and ILSS. For the four systems studied, the relative change was roughly proportional to the other measured quantities. This may have some very significant practical importance. It may point the way to use quick easy tests to screen and predict other behaviors for composites of different materials and/or processes. Perhaps a simple ER change test could be used to predict and select good candidate materials, surface processing techniques for high strength composite applications. The proportional relationship between interfacial adhesion and ER change was obtained by trend fitting line analyses. Ultimately, it was demonstrated that mechanical properties related to interfacial properties might potentially be predicted by ER measurement and studies of wetting behavior, using empirical formulas and correlations. Copyright 2016. Used by the Society of the Advancement of Material and Process Engineering with permission.