Preparation And Mechanical Properties Of 2D/3D Composite With Negative Poisson’s Ratio

The cellular structure has the advantages of light weight,high specific strength,and high specific stiffness.In recent years,many cellular structures have been applied in the field of aerospace.Compared with traditional cellular structure,metamaterials not only have the advantages of cellular structure,but also have the mechanical and physical properties that traditional materials do not have,which provides a new idea for solving engineering problems.As a kind of mechanical metamaterial discovered recently,negative Poisson’s ratio structure has attracted wide attention due to its properties of reverse contraction or expansion during compression or tension.Although the research of negative Poisson’s ratio structure has made some progress in recent years,there are still some key problems to be solved.Firstly,the bearing capacity of negative Poisson’s ratio structure is poor.Secondly,most negative Poisson’s ratio structures are difficult to produce due to their complex geometry.Finally,in different compression directions,the structure with negative Poisson’s ratio characteristics in omnidirection still needs further study.To solve these problems,an auxetic structure composed of corrugated sheets and tubes is fabricated by using high performance carbon fiber reinforced polymer(CFRP)composite material.By means of experiments,finite element simulation and theoretical analysis,the mechanical properties of auxetic structures of corrugated sheets and tubes composites are studied.The results show that the composite Cor Tube structure exhibits obvious negative Poisson’s ratio effect in a large range of compressive strain,and the auxetic properties of the composite Cor Tube structure become more significant with the increase of compressive strain.In the small strain stage,the stiffness of the structure depends on the thickness of the corrugated sheets,while in the large strain stage,the material parameters of the bellows play a decisive role.Finally,the deformation characteristics and failure modes of Cor Tube during compression are discussed.Then,in view of the problems such as easy unbonding and irregular failure in the compression process of the composite Cor Tube structure,the composite Cor Tube structure is improved,and the corrugated sheets tangent to the carbon fiber tube is used to prepare the carbon fiber reinforced composite Tan-Cor Tube structure with high performance.The mechanical properties of Tan-Cor Tube composite structures under quasi-static uniaxial compression and low speed impact loads are studied.The response of composite Tan-Cor Tube structure under quasi-static compression load is analyzed by theory,simulation,and experiment.A hemispherical rigid impactor was used to test the composite Tan-Cor Tube specimen with drop weight impact,and the effects of impact energy grade,impact position and thickness of corrugated sheet on impact response are investigated.The results show that the bonding strength of corrugated sheets and tubes can be improved by changing the cross section of corrugated sheet to arc section.And the main failure mode of the composite Tan-Cor Tube under quasistatic compression is the crushing damage of the tubes.Results also reveal that the composite Tan-Cor Tube structure could display notable auxetic characteristic under low-velocity impact.Higher bending stiffness of corrugated sheet leads to higher impact resistance.The main failure modes of the composite Tan-Cor Tube structure include cracks and pit on the corrugated sheets,crushing damage of the tubes and deboning between corrugated sheets and tubes.The maximum impact displacements of the specimens impacted at the peak are larger than those impacted at the valley,while the peak impact forces of the specimens impacted at the peak are lower than those impacted at the valley.And the results shed lights on the deformation process and failure modes of the composite auxetic structures under low-velocity impact.Finally,inspired by the conventional two-dimensional double arrow negative Poisson’s ratio structure and origami structure,a composite origami stack structure is designed and fabricated.In this study,the composite origami stack structure is prepared by hot molding process.A composite origami sheet with different Angle geometric parameters and thickness are designed and fabricated.Finite element simulation and compression tests are carried out to study its mechanical properties and deformation characteristics.The influence of the thickness of origami sheets and different angles on the auxetic properties of composite origami stack structures under the compression load of in-plane and out-of-plane is discussed.The results show that the composite origami stack structure has negative Poisson’s ratio in omni-direction.Finally,the failure mode of the structure during compression is analyzed,and the energy absorption capacity of the structure is compared with that of other multicellular materials.