Effect of spatial inhomogeneity in fiber packing on the strength variability of Al-matrix composites

Abstract

Nonuniform packing of fibers in Al₂O₃ fiber-reinforced Al-matrix composite (AMC) arises due to the pressure infiltration processing technique used for producing these composites. The effect of spatial variation in fiber volume fraction, f_L, on the strength variability of a Al-2Cu alloy matrix reinforced with 65 vol.% Nextel™-610 Al₂O₃ fibers was investigated. Measurements indicate a variance of ~7% in the f_L, much larger than the measured variance of ~3% in the specimen-to-specimen fiber volume fraction, f_G. An analytical model to account for the variance in f_G and f_L in predicting the Weibull modulus and the mean strength variation with the volume of AMCs is presented. This model incorporates the characteristic link concept and utilizes the theoretical predictions for their strength variability under local load sharing conditions. Comparisons of the model predictions with the experimental results of three- and four-point flexure, and tensile tests show excellent agreement.