Anti-Impact Characteristics And Bionic Structure Design Of Mantis Shrimp Dactyl Club

With the continuous development of science and industrial technology,the search for new material structures with high strength,high toughness and impact resistance properties has become an important research direction in the field of engineering.Organisms in nature have evolved naturally over millions of years to optimise and improve their structures and properties.Among them,mantis shrimp has evolved a pair of high strength and damage resistant dactyl clubs to adapt to the complex survival environment,and the relationship between its unique microstructure and mechanical behavior is of great significance to the design of new high-performance materials.In this paper,the microstructure,material composition and toughening mechanism of mantis shrimp dactyl club were studied by experiments,theoretical analysis and numerical simulation.On this basis,a bionic anti-impact structure was designed to study the effects of different structural parameters on the anti-impact performance of the bionic structure.The relevant studies and their conclusions were as follows.(1)Firstly,the microstructure and compositional composition of dactyl clubs were investigated.Significant differences in the microstructure of the different regions of dactyl club were found from scanning electron microscopy(SEM),which can be divided into three regions based on the arrangement of the fibers: the impact surface of longitudinal columnar arrangement,the impact region of sinusoidal arrangement and the periodic region of spiral arrangement.According to energy dispersive spectroscopy,Fourier transform infrared spectroscopy and Raman spectroscopy,dactyl club is a kind of natural composite composed of inorganic phases and organic phases.The inorganic phases are mainly hydroxyapatite,fluorapatite,calcium sulphate and calcium carbonate.Organic phases are mainly chitin and protein.The composition analysis shows that there are significant differences in composition between different regions,with a distinct gradient distribution.Apatite and calcium sulphate are concentrated on the impact surface,and are less in the impact region and disappear in the periodic region.In contrast,the relative content of calcium carbonate,chitin and protein was highest in the periodic region.(2)Secondly,the mechanical properties of natural and demineralized specimens from dactyl club were tested in quasi-static compression tests and combined with finite element simulations to elucidate the scientific mechanism for the orderly distribution of fibres in dactyl club.The results showed that the minerals maintain the structural characteristics of the fibres to improve the compressive strength.Observation of the fracture surfaces using SEM revealed that that the toughening mechanism of dactyl club was closely related to its unique fiber arrangement.Longitudinal fibers on the impact surface cause energy dissipation by buckling and producing microcracks,sinusoidal fibers in the impact region strengthen toughness by breaking and pulling fibers,and spiral fibers in the periodic region absorb the remaining damage energy through large deformation.Numerical simulation was used to validate the results,and it was further demonstrated that the arrangement of fibers can redistribute stress to improve overall yield resistance and energy absorption capacity and prevent catastrophic structural damage.(3)Finally,the fracture behaviour of dactyl club under impact loading was observed by means of a falling ball impact test,and a bionic impact-resistant structure was designed based on the characteristics of the microstructure of dactyl club.It was found that brittle fracture was likely to occur on the impact surface,which was caused by the intrinsic properties of mineral facies.However,the fiber structure in the impact and periodic regions changes and the brittle fracture became the ductile fracture.The results showed that the multi-layer structure of dactyl club and the arrangement of fibers in the microstructure were the main reasons for its impact resistance.Based on the structural characteristics of impact surface and impact region,a bionic anti-impact structure with controlling crack deflection was designed,and the crack propagation process was numerically simulated.The results showed that the longitudinal arrangement of fibers could improve the resistance to crack generation and propagation.This was due to the fact that longitudinal fibers dispersed stress over a larger area,helping to reduced stress concentration.In addition,the sinusoidal arrangement of the fiber could induce the crack to deviate from the vertical downwards direction and increase the energy dissipation by lengthening the crack path,so as to maintain the structural integrity.The results can provide new implications for the design of biomimetic anti-impact structures with crack reorientation and high damage tolerance,so as to improve the strength and toughness of the composites without changing the raw materials.