The purpose of this study is to better understand the mechanisms governing the phenomena of fiber/ matrix adhesion by controlling the fiber surface properties. This adhesion is evaluated by studying the micromechanical and thermodynamical behavior of the fiber/matrix interface. The complexity of the interactions at the interface requires a global approach that takes into account the chemistry, morphology, and mechanics. The thermodynamical affinity between the binder and fibers is evaluated by the wetting behavior, whereas the mechanical resistance of the fiber/ matrix interface is characterized with the pull-out test: Three distinct approaches are used to classify the different systems according to the nature of the binder and the fiber surface. It is found that there is better adhesion when the spin finish is removed from the fibers, revealing the surface roughness on which the latex can mechanically anchor. (c) 2006 Wiley Periodicals, Inc.