Evaluation of the Effect of a Custom Fiber Surface Treatment on the Adhesion Level in a Polymer-Based Composite Using the Single Fiber Fragmentation Test

During the past several years, a number of investigations have focused on improved fiber surface treatments as well as the development of micromechanical experimental techniques to accurately evaluate the fiber/matrix adhesion level. The aim of this study was to evaluate the effect of a custom fiber surface treatment on the fiber/matrix adhesion level of a carbon fiber reinforced, polymer matrix composite material. Single fiber fragmentation tests were performed on specimens produced using EPON 828 resin and AU-4 fibers, AS-4 fibers, and AU-4 fibers that were treated with a custom fiber surface treatment known to lead to direct chemical reaction with the EPON 828 resin. Qualitative inspection of the birefringent stress patterns produced by the custom treated fiber indicate a high level of fiber/matrix adhesion, greater than the adhesion exhibited by either of the two as received fiber types. In addition, the custom treated fibers produced an average fiber fragment length approximately 23% shorter than the AS-4 specimens, indicating a rather significant increase in adhesion level for the custom treated fibers over the commercially treated fibers. Calculated interfacial shear strength values follow the same trend as was seen during the evaluation of the average fragment length values.