Dynamic Response of Bio-Inspired Sutures

Biological suture interfaces are prevalent in various species in nature. Through mechanical modeling and experiments, it was found that the zigzag suture morphology is one key feature to maximize the overall strength and minimize the weight in resisting static mechanical loads. However, in different biological systems, the sutures often carry both static and dynamic loads, such as the cranial suture of mammals and the sutures on the beak of woodpeckers. The goal of this study is to quantify how suture interfaces respond to various dynamic loads. Two dimensional finite element (FE) models of two-phase composite sutures with various waviness (i.e. amplitude to wave-length ratio) are developed. Numerical simulations of sutures under both static and dynamic indentation are conducted. One auxetic and one non-auxetic designs are selected, both elastic and elasto-plastic material models are used for both phases. The influences of initial velocity, waviness, stiffness ratio between two phases, and auxeticity on the impact resistance of the materials are evaluated. In addition, selected designs are fabricated via a multi-material 3D printer (Stratasys Connex260). Drop tower mechanical experiments are performed to further quantify the dynamic response of bio-inspired composite sutures under various dynamic loads. It is found that shear and auxeticity play a very important role in mitigating impact loads.