On strength and toughness of soft staggered composites

In the search of light yet strong and tough materials the nature produced soft composites with the staggered architecture. In such design, a soft protein matrix connects rigid mineral platelets similar to the cement connecting bricks in construction. In the present work, we examine strength and toughness (the total energy dissipated in fracture) of soft composites from the “first principles”. The latter means that we do not postulate material strength and toughness in advance — they become an outcome of numerical solutions of the initial boundary value problem. We formulate the boundary value problem on the basis of the material-sink approach enforcing the damage description in constitutive equations. In addition to the classical nature-made staggered architecture, we examine some alternative possible designs of platelets inside the soft matrix. Comparisons show that the classical staggered design is the best one (among considered). Nature wins at the moment.