The spatial distribution of particles and the onset of damage determine important mechanical properties of composites. New algorithms were developed to generate composite microstructures with homogeneous and inhomogeneous (clustered) particle distributions, and the statistical parameters which characterize the reinforcement spatial distribution (radial distribution function, average nearest-neighbor distance, etc.) were determined. Cubic representative volume elements of the microstructures were discretized and analyzed by the finite element method. Particles were assumed to behave as linear elastic solids, while the matrix was modeled as an elasto-plastic solid with isotropic hardening. Damage in the matrix was introduced by the modified Gurson model while reinforcement fracture and interface decohesion at the matrix/reinforcement interface were included using three-dimensional interface elements especially developed to this purpose, the interface and/or particle strength and toughness being given by the constitutive equation of the cohesive crack.
The numerical results provided the macroscopic composite response as a function of the reinforcement volume fraction and spatial distribution, and showed how the details of the local particle arrangement controlled the nucleation and growth of damage in the composite throughout the three-dimensional microstructure. It was found that the overall composite response was weakly influenced by the reinforcement particle distribution in the absence of damage, although the maximum principal stresses in the particles at the local level were significantly higher in the clustered microstructures. Particle cluserteing, however, modified significantly the composite behavior when damage (as particle fracture, interface decohesion or ductile matrix failure) was included in the simulations.
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