Correlation of fiber pull-out strength and interfacial vibration damping techniques by micromechanical analysis

Adhesion between fiber and matrix in fiber-reinforced polymer composites pl ays an important role both in controlling mechanical properties and in the overall performance of composites. This suggests that analytical and experi mental methods to characterize the interface can be used to predict the mec hanical performance of the material. To this end, vibration damping techniq ues have been used as a non-destructive method to evaluate interfacial effe cts on composites. According to the theory of energy dissipation, the quali ty of the interfacial adhesion can be evaluated upon separating the predict ed internal energy dissipation associated with perfect adhesion from the me asured internal energy dissipation of a composite system; this enables the quantification of interfacial adhesion. A micromechanics-based model for ev aluating the adhesion between fiber and matrix from the damping characteris tic of a cantilever beam was developed that shows an inverse relationship b etween the damping contributed by the interface and its adhesion strength. A simple optical system was used to measure the damping factor of unidirect ional fiber-reinforced-polymer composites. Cantilever beam specimens contai ning either a single glass fiber or three types of single metallic wires em bedded in an epoxy resin matrix were tested. A correlation was found betwee n the measured interfacial adhesion strength directly from microbond pull-o ut tests and the micromechanics-based calculations from vibration damping e xperiments. (C) 1998 Kluwer Academic Publishers.