On composite-structure weaknesses: Part II. Computer experiments, identification, and correlation

Part II of this article concerns correlating the composite-structure weaknesses (CSWs) with the local microstructure of simulated short-fiber-reinforced metal-matrix composite (MMC) samples. The proposed analytically-numerically-based approach was employed for numerical computation of the mesoscopic stress distribution in short fibers. Nine local microstructure-related parameters are defined, which incorporate local elastic and thermal anisotropies into presentation of a local microstructure. It is found that the nine defined parameters are adequate physical parameters, which also account for synergetic interactions due to orientation-induced local anisotropies, either elastic anisotropy or thermal expansion anisotropy. By using the defined physical parameters, CSWs can be correlated with the local microstructure of simulated MMC samples. A database which collects numerical correspondences between the orientation and geometry of composite constituents and CSWs has been established for a number of simulated MMC samples. Computer experiments confirm that not only the stiffness mismatch between fiber and matrix materials, but also orientation-induced local anisotropies, exert decisive influence on the distribution of CSWs in short-fiber composites. The mesoscopic stress and strain distributions within a short fiber are critically dependent on the local evolution of elastic and thermal anisotropies of surrounding grains. Whether a CSW may become a failure origin must be evaluated in conjunction with a local damage mechanism.