Multi-materials3D Printing Application Of Shell Biomimetic Structure Research

In nature, many biological composite materials with precise micro structure and unbelievable mechanical performance. Pearl layer of shell due to its unique calcium carbonate and organic matter alternating multi-stage "brick-mud" structure, and excel-lent mechanical properties, is hot issue of biomimetic materials. This study have sig-nificance guiding on the highly ordered microstructure and toughening mechanism of many application domainsAs the study on the nacre composite material,3D printing is also popular technolo-gy in the field of rapid prototyping. With the development of three-dimensional printing technology, people’s inspiration can easily become a reality. Inspired by natural pearl layer’s high strength and high toughness, we use3D printing technology in the fabri-cation of biomimetic composite materials. Combined with theory of shear lag, tensile test and finite element analysis of composite material mechanics and coarse transition simulation we study on micro composite’s elastic modulus, fracture mode and fracture toughness.According to the composite fine mechanics in the short fiber composite with unit stress transfer mechanism,we derive the classical shear lag equations. On the basis of classical theory of shear lag, and in order to better describe the shell biomimetic mate-rials mechanical properties, we introduce the bricks model with end adhesive bonding of two-dimensional shell biomimetic unit. The model can used to describe the bionic composite unit internal stress distribution, elastic modulus and three different fracture modes. The subsequent introduction of Landau continuous phase transition free ener-gy theory and Muller’s double stability theory for understanding the tensile fluctuation curves.In the experimental part of this paper, we made different geometrical size, mud brick structure composite tensile specimens and crack propagation specimens. In the tensile test, we observed the detailed deformation stress state of the three main stages in tensile specimens. By changing the geometrical parameters of the tensile specimens, we obtain t three final failure modes, elastic modulus and geometrical dimension change trend and crack expansion during tensile loading.The simulation work in this study is divided into three parts. The first part is anal-ysis of periodic imitation shell element stress distribution, elastic modulus and micro structure size relationship, biomimetic composite structure of three kinds of fracture modes are analyzed, predict the bricks end crack nucleation region by using the finite element method. The second part is to use finite element method simulation imitation whole shell model of tensile, the imitation shell cracks from outside to inside of the progressive failure mechanism. The third part tells a coarse grained model, which is established through using double stability theory. The whole tensile curve of imitation shell level fluctuation mechanism are discussed in detail.In a word, this paper explores the stereolithography apparatus of3D printing tech-nology in the preparation and research of biomimetic composite materials. Young’s modulus, fracture mode and fracture toughness of the imitation nacre composite mate-rial were studied and has significance for the design of composite structure.