A computational fracture analysis is conducted on a self-healing particulate composite employing a finite element model of an actual microstructure. The key objective is to quantify the effects of the actual morphology and the fracture properties of the healing particles on the overall mechanical behaviour of the (MoSi2) particle-dispersed Yttria Stabilised Zirconia (YSZ) composite. To simulate fracture, a cohesive zone approach is utilised whereby cohesive elements are embedded throughout the finite element mesh allowing for arbitrary crack initiation and propagation in the microstructure. The fracture behaviour in terms of the composite strength and the percentage of fractured particles is reported as a function of the mismatch in fracture properties between the healing particles and the matrix as well as a function of particle/matrix interface strength and fracture energy. The study can be used as a guiding tool for designing an extrinsic self-healing material and understanding the effect of the healing particles on the overall mechanical properties of the material.

Research in the field of self-healing materials gained significant attention in the last decade owing to its promise of enhanced durability of the material components in engineering applications. Though the research has led to several successful demonstrations, extensive experimental tests will be required for a successful demonstration. Further, for real-time engineering applications with self-healing materials, arriving at an optimal design of the self-healing system is crucial. In this context, modelling techniques in combination with a limited number of experimental tests are potentially more efficient than a design process based on extensive experimental campaigns. With this motivation, the present thesis aims to develop a modelling framework to analyse and understand the fracture mechanisms and the healing behaviour of self-healing material systems using finite element modelling approach. The overall objective is to provide certain guidelines and suggestions for material scientists in terms of selection and design of healing particles and a computational tool to understand and quantify the cracking and healing behaviour of self-healing material systems.

The objective of this research is to explore the effect of microstructural defects on the mechanical properties of fiber reinforced composites. In particular, two kinds of defects are considered in the study, namely, matrix pores and interface precracks. Three-dimensional (3-D) finite element analyses are conducted on Representative Volume Elements (RVE) to predict the effective elastic properties of the transversely isotropic unidirectional composite with a random distribution of the pore defects and the results are reported. With regards to fracture properties, cohesive zone-based two-dimensional (2-D) finite elements are employed to simulate fracture in the microstructure, where the cohesive elements are embedded throughout the FE mesh to simulate arbitrary crack initiation and propagation. The results of the simulations are reported in terms of the fracture pattern and quantified using the effective stress-strain response for various volume and area fractions of matrix pores and interface cracks respectively. It is shown that the presence of defects has a noticeable influence on the elastic properties, but severely influences the fracture properties of the composite.