Natural materials are among the exclusive group of materials that have mesmerized the researchers throughout the world with their uniqueness and complexity, but at the same time being available and produced by nature in abundance. The natural composites or biocomposites have special mechanical properties in the sense that they are hard and tough at the same time. Hardness and toughness are two competing mechanisms such that one comes at the expense of the other. Natural composites such as nacre, shell, enamel and bones have produced materials with such superior mechanical properties. The study and analysis of such hard biocomposites by developing analytical models is the purpose and theme of this thesis.

Hard biocomposites have been identified to be a composite of mineral platelets and protein matrix. The mineral platelets are considered to be the smallest building block in the protein matrix. A single-rigid line inclusion (or anticrack) is considered to be a suitable representative of the mineral platelet. Stress and displacement fields around an anticrack will be studied and analyzed in this thesis. Some important implications based on such an analysis will also be made.

The hard biocomposites being analyzed in this work are considered to be having thousands of mineral platelets embedded in protein matrix. When such a dense collection of mineral platelets is observed in a composite, then there are bound to be interaction effects between two platelets close to each other. The study of such an interaction effect will be done in the last phase of this thesis – study of multiple anticracks. Finally a general analytical method will be developed at the culmination of this thesis which will pave the way for analytically analyzing the hard biocomposite as a whole.