Three dimensional characterization and modeling of particle reinforced metal matrix composites part II: damage characterization

This second paper of a two part sequence, attempts to quantitatively charac terize 3-D microstructural damage in particle reinforced metal matrix compo sites using a combination of computational and experimental tools. It is pe rhaps the first studies providing quantitative 3-D characterization of phas e and damage morphology for comparison with 2-D micrographs. Materials with different volume fractions and particle sizes, at different levels of defo rmation are considered. The serial sectioning method is used to obtain micr ographs of a series of parallel sections of the sample material. 3-D comput er images of the particles and the associated damage in the microstructure are constructed by digitally assembling the section micrographs. Equivalent microstructures with actual particles and cracks replaced by ellipses or e llipsoids are simulated for enhanced computational efficiency. The equivale nt microstructures are meshed into Voronoi cells by a surface based algorit hm. Various characterization functions of geometric parameters are generate d to identify the damage size, shape, orientation and spatial distribution both in 2- and in 3-D. A sensitivity analysis is conducted to explore the i nfluence of the morphological parameters on damage. Particle size, orientat ion and local volume fraction are found to play the most significant roles in the cracking process. Experimental observations of damage are compared w ith predictions by a probabilistic damage model viz. the Weibull model. Rep resentative material elements, which correspond to the characteristic sizes for local continuum representation, are investigated through the use of va riograms and marked correlation functions. (C) 1999 Elsevier Science S.A. A ll rights reserved.