Research On Shear Properties Of 3D Carbon-epoxy Woven Composites

Traditional 2D lamination composite has poor interlaminar shear performance and is prone to interlaminar failure.The 3D woven composite material made by braiding technology increases the shear performance in the thickness direction by increasing the fiber bundles approximately along the thickness direction.The mechanical properties and damage mechanism of 3D woven composites have been studied by researchers at home and abroad.However,the research mainly focuses on the study of tensile and compressive properties and impact properties.In t his paper,the microstructure,shear properties and damage and failure mechanism of 3D woven composites are studied and analyzed from two aspects of shear test and simulation analysis.Chapter 1 mainly introduces the background,purpose and significance of the research,analyzes the research progress of domestic and foreign scholars on the mechanical properties of 3D woven composites,and analyzes the shortcomings of the research in this direction,and introduces the work of this paper.In chapter 2,the static shear tests of 3D woven composites in plane are carried out,and the fatigue shear tests with different stress ratios in two directions in plane are also carried out.By analyzing the stress-strain curve of static shear,the failure morphology of specimens,the failure mode of shear fatigue and stiffness degradation,the shear performance of 3D woven composites is studied and analyzed.In chapter 3,the constitutive model of 3D woven composites is established,and Hashin damage criterion is used for damage analysis.After that,the microscopic structure of 3D woven composites is analyzed and studied,a modeling method for 3D woven composites is proposed,and the microscopic geometry model of 3D woven composites is established.In chapter 4,the geometric model and finite element model of 3D woven composites are established.The mechanical properties of 3D woven composites are obtained by simulation,and the validity of the numerical simulation model is verified by comparing the in-plane shear modulus and shear strength values of the test and numerical simulation,and the error of the test and numerical simulation results is analyzed.