Viscoplastic micromechanical response of three-dimensional, two-phase unit cell composites with particles at regular positions

A Fast Fourier Transform (FFT)-based viscoplasticity simulation is performed to study the microstructure -property relationship of the unit cell metal-metal composites. Three-dimensional digital unit cell composites, composed of single-crystalline hard BCC particles at "regular" positions and a single-crystalline soft FCC matrix, are used as instantiations to calculate the stress and strain-rate fields under uniaxial tension. Such "regular" unit cell composites are generated by growing particles from either simple cubic, body centered cubic or face centered cubic grid points, having particle volume fractions from 0.1 to 0.9. Topologically, each type of regular unit cell is found to be unique. Moreover, its topological measures change drastically once particles initiate simultaneous contacts. While the macroscopic mechanical behavior as a function of the particle volume fraction is insensitive to the type of the unit cell, the local micromechanical response of each phase shows a strong dependence both on the morphological evolution as a function of the particle volume fraction as well as on the type of the unit cell. However, such morphological effects on the local mechanical response weaken when the matrix has a hard crystallographic orientation with respect to the tension direction. No single determining microstructural feature could by itself explain the complex variation in the micromechanical response of the unit cell composite.