Mechanical behavior of 3D printed biomimetic Koch fractal contact and interlocking

Inspired by the hierarchical/fractal topological interlocking in nature, Koch fractal interlocking with different numbers of iteration N are designed. To better understand the mechanics of fractal interlocking, the designs are also fabricated via a multi-material 3D printer. Mechanical experiments and finite element (FE) simulations are performed to further explore the mechanical performance of the new designs. Analytical model is also developed to capture the deformation mechanisms of the fractal interlocking through contact. It is found that the load-bearing capacity of Koch fractal interlocking can be effectively increased via fractal design. However, the mechanical responses of fractal interlocks are also sensitive to imperfections, such as the gap between the interlocked pieces and the rounded tips. When fractal complexity increases, the mechanical properties will become more and more sensitive to the imperfection and eventually, the influences from imperfection can even become dominant. By considering the influences of imperfection, the theoretical model predicts the existence of an optimal level of fractal complexity for maximizing mechanical performance. (C) 2018 Elsevier Ltd. All rights reserved.