Experimental Study And Numerical Simulation Of Dynamic Fracture Behavior Of Biomimetic Composites Under Impact Loading

With the development of science and technology,human beings have higher requirements for materials,resulting in the birth of composites with light weight,high strength,anti-corrosion,water resistance,fire resistance and other properties.After millions of years of evolution,almost all natural materials have elegant,fine and organized structures,showing excellent impact resistance and damage tolerance.In recent years,incremental manufacturing methods such as 3D printing enable researchers to use this material to create complex microstructure,which has been widely used to study the structure-performance relationship.These studies lack a systematic and fair comparison,but different biological structures should have different properties according to different functions and load conditions.The study of their advantages and disadvantages is very helpful for the practical design of new biomimetic composites.Biomimetic composites have excellent static and dynamic mechanical properties,but so far,there are not many studies on the effect of micro-size on fracture toughness and crack propagation in biomimetic composites under dynamic loading,hence,it is of great significance to study the influence of different structural parameters on the dynamic fracture behavior of biomimetic composites.The main work of this paper was divided into three parts.In the first part,the quasi-static mechanical properties of Vero White Plus resin and Tangoplus viscoelastic materials used for3 D printing were studied,including quasi-static compression and tension,and the mechanical parameters of the two matrix materials were obtained.In the second part,the dynamic fracture behavior of paste layered biomimetic composites was studied.Firstly,the samples of paste layered biomimetic composites with different aspect ratio and adhesive layer thickness were designed,and then the dynamic three-point bending impact test of split Hopkinson bar was adopted.Finally,a full-scale experimental model was established by using ABAQUS finite element analysis software for numerical simulation.The effects of bonding layer thickness,aspect ratio and other parameters on the dynamic fracture behavior of paste layered biomimetic composites were studied and analyzed.The experimental and numerical simulation results show that the cushioning and energy absorption characteristics of the soft material layer delay and hinder the crack propagation and affect the impact fracture resistance of the specimen.With the increase of the aspect ratio of the hard material and the decrease of the thickness of the soft material layer,the more the crack tends to "pass through" rather than "bypass" the hard material,the greater the peak impact resistance.In the third part,the dynamic fracture behavior of branch staggered layered biomimetic composites was studied.Firstly,the branch staggered laminated biomimetic composites with different aspect ratio and adhesive layer thickness were designed,and then the three-point bending test of split Hopkinson bar and ABAQUS numerical simulation method were used to study and analyze the effects of impact velocity,aspect ratio and soft rubber layer thickness on the dynamic fracture properties of 3D printed branch staggered laminated biomimetic composites.The experimental results show that when the structure of the sample is the same,the ability of the crack to pass through the interface between the hard material and the matrix material increases with the increase of the impact velocity and the aspect ratio of the hard material and the decrease of the thickness of the soft adhesive layer.The more inclined to propagate along the straight line through the hard material,the peak dynamic load and initiation work increase,and the overall structure of the sample is more brittle.On the contrary,the ability of the crack to pass through the interface between the hard material and the matrix material is also weakened.The more it tends to avoid the hard material and propagate along the broken line through the soft material,the peak dynamic load and crack initiation work decrease,and the toughening effect of the sample is better.The finite element simulation results show that the fracture toughness of the sample increases with the increase of width,and the crack tends to bypass the hard material and propagate along the soft glue layer.Using the impact direction designed by the experiment,the fracture toughness of the sample is higher than that of other directions.