Particle reinforced composites generally consist of a high strength, high stiffness distributed phase (particles) embedded in a softer continuous phase called the matrix. The mechanical behavior of these composites is influenced by several factors, such as volume fraction, particle size, particle morphology, distribution of particles, and particle fracture strength. A fundamental understanding of the influence of these factors on the tensile and crack growth behavior of the composite is still lacking. Numerical modeling, such as finite element modeling, can be used to simulate and understand the tensile behavior and crack growth behavior of these composites.

In the first part of this research, the influence of the distribution of reinforcement particles on the tensile behavior of the composite was examined. An Al-SiC system was chosen in this study as the model system. To study the effect of particle distribution, the SiC particles were represented as two-dimensional discs with uniform diameter. The initiation and progress of damage by particle fracture was also modeled. Initially, all SiC particles were assumed to have uniform fracture strengths. Three particle distributions—ordered, random, and clustered were evaluated. The degree of particle clustering was quantified using the coefficient of variance of the mean near-neighbor distance method. The particle fracture strengths were also varied using Weibull statistics. It was found that an ordered SiC distribution was not necessarily the best distribution when the particle fracture strengths were not uniform.

In the second part of this research, a microstructure-based modeling technique was developed to study crack growth in particle-reinforced composites. With this technique, it was possible to capture the real microstructure of the composite. The effects of particle morphology and distribution (random and clustered) on crack growth were studied. A re-meshing algorithm was used to model crack propagation. Two dimensional linear elastic fracture mechanics principles were used to propagate the crack, and to gain an understanding of the local stress state. The effect of particle fracture on crack growth was also studied. It was observed that particle fracture ahead of the crack tip significantly altered the crack trajectory and the stress intensity values at the crack-tip.