On composite-structure weaknesses: Part I. Simulation, properties, and numerical approach

Abstract

Composite material samples were created by means of computer simulation to duplicate short-fiberreinforced metal-matrix composites (MMCs). Each sample contains a fairly large number of Voronoi grains and ellipsoidal short fibers, which orient and distribute in a random manner, to mimic composite microstructures for investigating the coherent interconnections of composite-structure weaknesses (CSWs) with local microstructure. It is supposed that the samples are subjected to coupled boundary traction due to mechanical loading and thermal cycling. A Kröner-Kneer structure-based model and Waldvogel-Rodin algorithm were used for numerical computations of the mesoscopic stress distribution in constituent grains. The computations are based on the grain-volume average of local fields. Polycrystal elastic/thermal properties and effective elastic/thermal properties of simulated MMC samples were predicted, respectively, in terms of micromechanics models, in favor of incorporating the influences of macroscopic material properties on the formation of CSWs. An analytically-numerically-based approach is proposed for analyzing peak mesoscopic stress and strain distributions in short fibers. Three crucial aspects constitute a kernel of the approach, i.e., (1) segmentation of short fibers, (2) establishment of the geometric relations of a short fiber to the surrounding grains, and (3) the local nature of micromechanics. The analytically-numerically-based approach takes into account the grain orientation, fiber orientation, grain geometry, fiber geometry, and macroscopic properties of simulated MMC samples. The Numerical Assessment of Computer-Imitated Weaknesses-MMCs (NACIW-MMCs) software program has been developed for performing simulation of the microstructure of short-fiber-reinforced MMCs and executing all involved numerical computations.

Visualized simulation and modularized architecture of microstructures for composite materials

“…Nevertheless, from a viewpoint of microstructure characterization, local microstructural details in both geometry and crystallographic orientation must be available during simulation, sufficient enough for statistical analyses and ready for presentations of local microstructure. The philosophy innovated in microstructure modeling at the material size of mesoscopic scale is that local geometries and orientations of material constituents, rather than simplified microstructure as a whole, determine local responses [1,13] and hence the size of representative volume element of the microstructure. Obviously, this requires one to imitate geometric profile of local microstructure details in a visualized manner when generating the microstructure.…”

“…Therefore, this approach has generated great interest and one pays increasing attention to interrelations between a real or invented microstructure and resultant material properties, particularly synergetic effects of local combinations of orientation and geometry of material constituents on the material properties. In this regard, computer-based experiments on the microstructure may offer a powerful means of investigating these synergetic effects more effectively [1].…”