Bionic Structure Design And Performance Research Based On The Structural Dimension Elements Of Pearl Layer Of Hyriopsis Cumingii

The pearl layer of natural shell has attracted great attention due to its unique microstructure and high-strength and toughness.The pearl layer of shell is composed of a small amount of organic matter and a large amount of Ca CO₃ stacked into a complex and ordered“brick-mud”structure,which shows excellent strength and toughness.Therefore,the microstructure of pearl layer has become a model for preparing composite materials with high-strength and toughness.In this paper,the microstructure,structure size,composition phase,thermal stability,nano indentation property,three-point bending property and tensile property of the pearl layer of Hyriopsis cumingii were systematically studied.The effect of heat treatment on the mechanical behavior of the pearl layer of the shell was compared and analyzed,and the relationship between the microstructure and mechanical properties of the pearl layer of the shell was discussed.The results show that the pearl layer is composed of hexagonal aragonite chips and organic matter,with a thickness of 1000-2800?m,a side length of 1-4?m and a thickness of 200-700nm.The pearl layer accounts for an absolute proportion in the shell,and the ratio of the side length to the thickness of aragonite chips is about 2-6times.The elastic modulus and hardness of pearl layer are high in the middle and low at both ends of the 0growth line.The elastic modulus and hardness of fresh pearl layer are about 53GPa and2.9GPa.The bending strength and modulus of pearl layer increase first and then keep sinusoidal wave on the 0 growth line,and the bending strength and modulus in the middle and rear part are higher than that in the front part.The average bending strength and modulus of fresh pearl layer are 164MPa and 35GPa respectively.The tensile strength and modulus of pearl layer decrease first and keep stable in the middle part,but decrease gradually in the back part,The average tensile strength and modulus of fresh pearl layer are 37.8MPa and 4.3GPa respectively.After heat treatment,the mechanical properties of pearl layer decrease obviously,indicating that the organic matter content is low but essential.Based on the research of pearl layer,this paper abstracts the structural elements of the pearl layer,establishes the primary structural model,and designs the primary structure of bionic pearl layer.The primary pearl layer structures of bionic shell with different thickness ratio and length thickness ratio were prepared by vacuum diffusion welding and melting deposition forming technology respectively.The effect of thickness ratio of different strength material and soft material on the mechanical properties of primary pearl layer structures of bionic shell was studied.The results show that in different thickness ratio structures,with the increase of thickness ratio of strong material and soft material,the impact toughness gradually decreases,and the bending strength gradually increases,which is the best when the thickness ratio is 2:1,the impact toughness is 168J/cm²,and the bending strength is 716MPa.Compared with the composite weighted material volume ratio,the bending strength is only reduced by4%,and the impact toughness is increased by 63%.The influence of the length thickness ratio of different strength elements on the mechanical properties of primary pearl layer structures of bionic shells was studied.The results show that in different length thickness ratio structures,with the increase of the length thickness ratio of the strong material elements,the impact toughness first increases,then decreases and increases,and the bending strength first increases and then decreases.The optimal length thickness ratio is 2.5:1.At this time,the impact toughness is 7.1J/cm²,and the bending strength is 47MPa.Compared with the composite weighted property of material volume ratio,the bending strength is only reduced by 2%,while the impact toughness is increased by 1.6times.