Role of modulus mismatch on crack propagation and toughness enhancement in bioinspired composites.

Natural materials such as nacre exhibit a high resistance to crack propagation, inspiring the development of artificial composites imitating the structure of these biological composites. We use a phase field approach to study the role played by the elastic modulus mismatch between stiff and soft layers on crack propagation in such bioinspired composites. Our simulations show that the introduction of a thin layer of a soft phase in a stiff matrix can lead to arrest of a propagating crack and can also lead to crack branching. The crack branching observed in the phase field model is analyzed using a cohesive zone approach. Further, we show that the toughness of such a composite can be substantially higher than that of its constituents.