Impact Mechanics Behavior Of Multi-component Hierarchical Composite Structure Based On Bionics

After millions of years of survival of the fittest,most of the natural organisms that can survive in the nature have evolved unique structure and function.Although these natural organisms are composed of relatively single components,their unique micro-structure endows them with excellent mechanical properties.The shell nacreous layer,conch shell and mantis shrimp finger joint are all composite materials composed of a large amount of inorganic calcium carbonate and a small amount of organic matrix,but their respective structural characteristics give them incomparable properties of synthetic materials.The shell nacreous layer is a kind of brick and mortar structure formed by the inlaid arrangement of soft and stiff materials.There are various forms of interaction between the lamellar layers which make the shell have high strength and toughness.Conch shell internal level is a kind of three layers of cross-lamellar structure,by the outside world after baiting,crack in the cross-lamellar structure will be in a "Z" type of path for transmission,super long crack propagation path gives strength and hardness of the conch shell than other structures,for helmets and body armor and other protective equipment manufacturing provides a good design;Mantis shrimp knuckles is a kind of unique plywood spiral arrangement structure,when prey on other organisms or hit,the structure of the spiral arrangement will produce a large number of nested micro cracks,micro cracks will gradually spread along the spiral arrangement of plywood,avoid catastrophic damage,the overall structure and gives a mantis shrimp knuckles high strength and toughness.The arrangement characteristics of various natural biological microstructures provide a good idea for the development of composite structures.Therefore,it is of great significance to study the structural characteristics of natural bio-materials and construct various kinds of composite structures with structures imitating natural bio-materials.The main research content of this paper is to construct various bio-mimetic models of natural bio-material structures,and to study the effects of different arrangement,material volume fraction and impact velocity on the properties of bio-mimetic structures through experiments and finite element simulation.This paper mainly does the following two parts of the research work:The first part is the experiment part,first of all,through the increase of material manufacturing technology to print two kinds of substrate materials standard parts,and in a quasi static pressure and dynamic pressure was carried out under the condition of experiment,the two kinds of basic mechanical properties of substrate material,the results show that is a kind of brittle and hard material strain rate sensitive material,soft materials are greatly influenced by strain rate.Then,combined with additive manufacturing,drop weight experiment and digital image correlation(DIC)technology,three kinds of natural biological structures and soft and hard substrate plate-like specimens were studied,and the similarities and differences of different structures in performance and the overall deformation mode of the models were compared.The results show that the three biomimetic structures have their own advantages in the properties(bearing capacity,compressible deformation,energy absorption),and the three bio-mimetic structures have achieved a performance compromise,no longer have some extreme mechanical properties like the matrix materials.The second part is the finite element simulation.Firstly,the correctness and rationality of the matrix material and composite structure model are verified through experiments,and the mesh sensitivity is verified.Then,different types of bionic composite structures were designed,and the finite element simulation was carried out under different impact velocities.The effects of different types of designs on the bearing capacity,deformation mode and energy absorption capacity of the structures were analyzed.The finite element results show that the structural performance can be greatly improved by changing the arrangement of the structure and the volume ratio of soft and stiff materials.Generally,the model with brick and mortar arrangement can exhibit a layered failure mode under low speed impact,and the maximum compression displacement can be achieved is greater than that of the model with the aligned arrangement.Different volume fraction ratio on the structure of the stiff and soft materials have great influence bearing capacity and energy absorption ability,generally lower content of soft material model has higher bearing capacity,but its compression deformation and great influence on the energy absorption capacity,large volume of soft material can increase the structural deformation and energy absorption ability,but its bearing capacity will be greatly affected,reasonable configuration of the structure of the stiff and soft material proportion,can achieve bearing capacity,deformation capacity and energy absorption ability of the perfect combination of,for the manufacture of new protective equipment to provide good design ideas and data support.