Impact Resistance,fracture Resistance And Elastic Wave Propagation Characteristics Of The Bouligand Structures

After hundreds of millions of years of natural selection,biomaterial systems with nanoscale soft phase organic matter and hard phase inorganic minerals as raw materials have constructed complex and highly ordered multi-level and multi-scale structures under the regulation and control of life activities,thus possessing unique mechanical and physical properties to achieve their own specific functions.Driven by the competitive law of survival of the fittest,biomaterials can obtain high structural efficiency at a very low cost,which is of great significance to the theoretical research and engineering development of new materials.Learn from nature,by taking inspiration and experience from nature,imitate the shape,multi-level and multi-scale structure of biomaterials.From the perspective of mechanical design,a comprehensive and in-depth analysis and understanding of its formation principle,and then the establishment of related design theories and methods of biomimetic materials,can provide a new way to create new high-performance artificial materials.In This paper,the Bouligand structure evolved from the limbs of typical arthropods(shrimps and crabs)was taken as the research object.The mechanism of excellent mechanical/physical properties of the Bouligand structure is analyzed.The relationship between the impact resistance,fracture resistance and elastic wave propagation characteristics of the composites and the factors such as the structural configuration,the material properties of the components and the interface characteristics of the composites is clarified.The design method,mechanical testing and failure mechanism of B ouligand-type biomimetic composite laminates are studied.This article includes the following four parts:Firstly,the research on the impact resistance and mechanism of the Bouligand structure is carried out.According to the configuration of the Bouligand structure,a dynamic mechanical behavior analysis model of Bouligand structure considering the contact between the spiral stacked fibers is established,and the validity of the model is verified by comparing with the impact response test data.Furthermore,the influence of the characteristic parameters(pitch angle,pitch,laminate thickness and material properties)on the impact resistance of the structure is systematically analyzed,and it is revealed that the local velocity perturbation and redistribution effect are the impact resistance mechanism of the structure.The effect of fiber scale(from mesoscopic to macroscopic)on the impact resistance of the structure is analyzed,and the possibility of the application of the B ouligand bionic strategy in the design of impact-resistant composites is analyzed.Then,the characteristics of elastic wave propagation and its regulation in the Bouligand structure are studied.Based on the transfer matrix method,a theoretical model of elastic wave propagation in Bouligand structure considering interface characteristics is established.The dispersion curves of longitudinal wave and shear wave predicted by the model are in good agreement with the analytical solutions in the literature,which verifies the validity of the model.The relationship between the onset frequency of the elastic wave band gap and the size of the Bouligand structure is quantitatively characterized by the factors such as the pitch angle,the material properties and the interlayer characteristics.Based on the theory of detuned phononic crystals,the analytical model of the reflection and transmission coefficients of elastic waves in a Bouligand structure with a pitch gradient is derived.The gradient structure can more effectively suppress the propagation of the middle and high frequency components of the elastic waves,and the energy dissipation ability of the gradient structure under the predation load of the mantis shrimp is quantitatively characterized by calculation,and the impact resistance mechanism of the mantis shrimp dactyl club is revealed from the band gap characteristics of the gradient structure.Next,the theoretical analysis of the fracture characteristics of the Bouligand structure under quasi-static loading is carried out.In This paper,an analytical model for the driving force of the crack propagation in the Bouligand structure with the mixed fracture mode is established by using the theory of material configuration force and fracture mechanics,and then a numerical method for the strain energy release rate at the crack tip in the Bouligand structure is given.The maximum energy release rate criterion is used to simulate and analyze the crack propagation of the Bouligand structure with single edgecrack under uniaxial tension,and the influence of the pitch angle and material properties on the fracture behavior of the Bouligand structure is given,thus revealing the toughening mechanism of the torsional crack propagation of the Bouligand structure.A finite element analysis(FEA)model of the double-twisted Bouligand structure(a kind of variant configuration of Bouligand structure)is established by considering the fiber arrangement configuration and the bridging fiber between layers.The effects of the bridging fiber on the delamination resistance and the equivalent elastic modulus of the double-twisted Bouligand structure are quantitatively evaluated,and a finite element simulation model of the single-edge crack extension of the BRIGG structure is established.The failure load,failure displacement and anti-damage fracture performance of the two different fiber arrangements were compared and analyzed,and it was found that the double-twisted fiber arrangement could further improve the anti-damage fracture performance of the Bouligand structure.Finally,the design and fabrication of the Bouligand-type biomimetic composite laminates,the mechanical properties and failure mechanism under bending and low-velocity impact loading were studied.The distribution of thermal residual stress and deformation in the laminates pr epared by thermoforming is analyzed by using the classical laminate theory,and the design criteria of the Bouligand-type biomimetic laminates are given.The semianalytical formulas of interlaminar damage mechanism and fracture toughness under different interfacial angles were obtained by the tensile tests of double cantilever beams and bending tests with edge notches,and the mechanical behavior and failure mechanism of the Bouligand-type biomimetic laminates under three-point bending were analyzed by the combination of experiments and simulation analysis.The influence of pitch angle,layer thickness and material properties on the bending mechanical behavior of the structure is simulated and analyzed.The dynamic mechanical behavior of the laminated plate was analyzed and predicted by the combination of simulation and experiment,and the anti-impact performance of the laminated plate was verified.Furthermore,the effect of the pitch angle on the impact resistance(peak impact load,energy absorption rate)of Bouligand-type biomimetic laminates was quantitatively studied.The prediction method of the energy dissipation performance of Bouligand structure under dynamic and static loads established in this paper can help us to deeply and fully understand the formation principle of Bouligand structure biomaterials in nature and the internal relationship between structure and performance.In this paper,with the help of a specific biological structure,the mechanical and physical performance advantages of the str ucture are deeply explored.It is of great significance to expand the research idea of realizing multi-functional integrated structure,which opens up a new idea for the design of multi-functional composite materials for aerospace,and promotes the intersection and integration of solid mechanics and biomaterial mechanics,and has a very important practical significance and broad application prospects.