Strengthening And Toughening Mechanism And Performance Optimization Of Biomimetic Mantis Shrimp Helical Layered Structure

Lightweight and high-strength materials are of great significance for energy saving,emission reduction and operating cost reduction,and have become key materials in many advanced fields,such as aerospace,national defense,military and rail transit.As a new type of composite material,biomimetic structural material has a fine hierarchical structure,which coordinates and optimizes the mechanical properties such as strength and toughness at different scales.In recent years,scientists have constructed a series of new lightweight biomimetic composites with high strength and toughness by imitating the internal hierarchical structure of natural biomaterials,which provides a new way for lightweight design and performance optimization of materials.For example,in the past few decades,researchers have used the “brick-mortar” laminated structure inside the shell pearl layer as a model system for toughening biological composites.In order to simulate the pearl-shaped “brick-mortar”laminated structure,a lot of work has been done.However,recent studies have found that mantis shrimp use hammer-shaped rods to break the shells of mollusks and other mollusks for predation,so the mantis shrimp rods have to withstand thousands of high-speed and violent impacts,which puts forward high requirements for its anti-impact performance.Because the shell of mantis shrimp rods is a helical structure composed of chitin fiber bundles,it not only is lightweight,but also is high strength and toughness.This not only provides an important reference for material design for the development of many high-tech fields,but also provides the possibility for innovation in many new scientific and technological fields.It is well known that the damage resistance of laminated composites along the thickness direction is poor during the load-bearing process.In this paper,inspired by the chitin fiber helical arrangement structure(Bouligand system structure)inside the mantis shrimp rod,the unidirectional carbon fiber prepreg(carbon fiber bundle and epoxy resin reinforced composite)was creatively laid into a helical lamination structure inspired by the mantis shrimp stick,and then different interlayer helix angles were designed.Different helical laminated samples were prepared by laminating unidirectional carbon fiber prepreg according to different helical angles between layers.The static bending loading experiments of the prepared samples were carried out on the Instron5544 material tension-compression testing machine,and the mechanical behavior under bending load and the corresponding strength and toughness(energy absorption)properties were obtained.The fracture surface was characterized by scanning electron microscope,and the micro-morphology of the fracture surface was observed.Finally,the helical structure model is established by using ABAQUS finite element numerical simulation software,and the static ballast process of bionic helical structure is numerically simulated.Combined with the simulation results and experimental results,the strength and toughness mechanism of the bionic helical layered structure is analyzed,and it is found that there are complex intralaminar and interlaminar stress distribution in the helical structure in the process of deformation and failure,which has an important impact on the load transfer efficiency.With the change of the interlayer helix angle,the stress distribution within and between these layers will change significantly.Under the action of tensile stress in each layer,the fracture of carbon fiber along the direction of carbon fiber,the rupture of matrix in the direction of vertical carbon fiber and the debonding between fiber and matrix will occur in each single layer.At the same time,the shear stress between the adjacent thin layers is analyzed,and the helical progressive damage may occur between the adjacent thin layers under the action of interlaminar shear stress.The results show that the damage mechanism induced by tensile stress in layers and the progressive damage mechanism induced by interlaminar shear stress have key effects on the bearing capacity and energy absorption of helical structures.Strength and toughness are a pair of incompatible contradictions for most materials.Exploring the combined optimization mechanism of strength and toughness of materials is an important research topic in the field of lightweight materials.Inspired by the biology of nature,on the basis of the previous work of bionic helical layered structure,this paper combines the helical layered “Bouligand” structure inside the mantis shrimp rods with the “brick-mortar”laminated structure inside the pearl layer of the shell,and uses the carbon fiber epoxy resin composite thin layer to prepare a new composite with secondary structure.The deformation failure and energy absorption characteristics of a single helical laminated structure material under bending load are compared with that of a single helical laminated structure material.Through the study,it is found that in the process of deformation and failure,the samples with both “brick-mortar” staggered laminated structure and helical laminated structure can improve their internal stress distribution and load transfer efficiency,alleviate local stress concentration and delay material failure,and prevent crack propagation,so as to further improve the bearing capacity and energy absorption capacity of materials.Therefore,the new structure obtained by combining the helical layered structure inside the mantis shrimp rods with the “brick-mortar” laminated structure inside the pearl layer of the shell has a positive guiding significance for the internal structure design and performance optimization of lightweight and high-strength materials.