Modification of Fiber-Matrix Bond Strength through Surface Treatments

摘要

A model system of Ni-Cr wires in a vinyl ester resin matrix is used to study therneffect of surface treatments on shear bond in axisymmetric macrobond tests. Arnstress-based approach presented by Zhandarov and colleagues is modified to allowrntests with different fiber diameters to be compared on the same plot of averagernshear stress at debond, τd versus embedment length divided by fiber diameter, le/df.rnTwo parameters are used to fit the theoretical equation to experimental data. Onernparameter, c, is related to the shear lag parameter, β, and controls the shape of therncurve. This parameter is nearly constant in the range of geometries considered inrnthis work. The second parameter is the ultimate shear stress, τult, which is the valuernof the fitted curve at le/df equal to zero. As c is nearly constant for the geometriesrnconsidered, the same value of c is used to explicitly solve for τult for additional testsrnwhere the surfaces of the Ni-Cr wires were modified via baths in sulfuric acid. Thisrntreatment resulted in significant increases in τult, albeit with increased scatter in thernresults. Specific results of surface treatments are discussed. This work establishesrna framework for developing micromechanical models for bond strength based onrnmeasureable characteristics of the surface with the ultimate goal of developingrnmicromechanical models to predict the effect of surface treatment a priori.