Experimental Research And Numerical Simulation Of Fracture Toughness Of Biomimetic Spiral Structured Composite

Bouligand structure found in dactyl clubs is a layered helical structure.This structure periodically stacks layers of the same height so that each layer is deflected by a certain angle from the adjacent layer.The bionic spiral structured composite material has excellent mechanical properties of high strength and high toughness.The hammer-like claws of the odontodactylus scyllarus shrimp are representative of this fine structure.It can easily break the shells of shells such as shells and crab shells with its claws.The claws of the guinea mantis shrimp can withstand high-speed and multiple impacts,and have high toughness and damage resistance.The shell of mantis shrimp rods is a helical structure composed of chitin fiber bundles,it has a lighter weight and also has excellent mechanical properties.This provides research ideas for new lightweight composite materials,which can be widely used in high-tech fields such as aerospace and biological protection.Therefore,the research on bionic helical composites has important engineering practical application significance.The main research content of this paper is divided into two parts.In the first part,the dynamic three-point bending experiment of biomimetic spiral structured composites was carried out using split Hopkinson,and numerical simulation was carried out by ABAQUS to study the dynamic fracture toughness of biomimetic spiral structured composites.In the second part,the quasi-static three-point bending experiment was carried out on the bionic spiral structured composite material,and the fracture toughness of the material was analyzed under the quasi-static condition.In the dynamic three-point bending experiment.First,8 groups of specimens with different angles were prepared by 3D printing technology using two kinds of substrates,soft and stiff,and the dynamic three-point bending impact tested were completed by using an improved split Hopkinson bar.Obtain displacement-load curve,fracture time and fracture energy,and analyzed the final fracture shape of the sample.Analyze the fracture morphology of the sample.Both the experimental and numerical simulation results show that the helix angle has a great influence on the fracture toughness of the specimen.In the range of the helix angle of 0°-75°,the fracture toughness of the specimen increases form the increase in the angle.But when the helix angle is 90°,the fracture toughness of the sample drops sharply.At the same time,it was observed that there was a crack deflection phenomenon during the dynamic fracture process of the sample,and the influence mechanism of the crack deflection on the dynamic fracture was investigated.The results showed that the crack deflection changed the local fracture mode of the composite material,increased the fracture area,and improved the fracture toughness of the material.In the quasi-static three-point bending experiment,7 groups of samples with different helix angles were prepared using the same 3D printing technology,and the quasi-static three-point bending experiment was carried out on the bionic helical composite material using the Wanqi experimental instrument.The load-displacement curves of different angles were finally obtained through quasi-static experiments,and the crack propagation,fracture work and volume ratio of the samples were studied and analyzed,and the static stress intensity factor of the samples was solved.In the quasi-static experiment,the sample with part of the helix angle did not break completely,which is different from the dynamic experiment.By comparing the volume ratio of the soft and hard matrix of the sample,it is found that the helix angle is an important factor in determining the mechanical properties of the sample.The fracture work and static stress intensity factor of the specimen with a helix angle of 75° are the largest,and the fracture does not occur completely,and the crack deflects when the crack expands.There is an optimal helix angle around 75°,which can make the mechanical properties of the bionic helical composite material to be optimal.