  Hierarchical microstructures are often invoked to explain the high resilience
and fracture toughness of biological materials such as bone and nacre.
Biomimetic material models inspired by those structural arrangements face the
obvious challenge of capturing their inherent multi-scale complexity, both in
experiments and in simulations. To study the influence of hierarchical
microstructural patterns in fracture behavior, we propose a large scale
three-dimensional hierarchical beam-element simulation framework, where we
generalize the constitutive behavior of Timoshenko beam elasticity and Maximum
Distortion Energy Theory failure criteria to the complex case of hierarchical
networks of approximately 5 million elements. We perform a statistical study of
stress-strain relationships and fracture surface mophologies, and conclude that
hierarchical systems are capable of arresting crack propagation, an ability
that reduces their sensitivity to pre-existing damage and enhances their fault
tolerance compared to reference generic fibrous materials.
