Research On Microstructure And Mechanical Properties Of 3D Nonorthogonal Woven Composites

3D nonorthogonal woven composite is a kind new composite structure that based on classical 3D woven composite.Compared with classical 3D woven composite,it has the common advantages along with its own superiority.In this thesis,investigations on the followig aspects of 3D nonorthogonal woven composite are conducted.Firstly,microstructure of 3D nonorthogonal woven composite are studied.The yarn alignment in space is obtained.Based on the previous steps,representative volume cell of 3D nonorthogonal woven composite is established in 3D modelling software CATIA.Secondly,3D nonorthogonal woven composite panels were molded by the resin transfer modelling technology.The composite panels were cut into testing specimens.Quasi-static tensile test was carried out to determine Young's modulus and Poisson's ration of 3D nonorthogonal woven composite.Thirdly,by employing stiffness averaging method,3D nonorthogonal woven composite is validated as an orthogonal material.By adopting this method and Kregers' weighted average model,engineering elastic constants are obtained.The results derived by theoretical method agree well with experimental data.Lastly,finite element analysis is carried out to study elastic properties of 3D nonorthogonal woven composite.The results obtained by FEM are in good agreement with experiment result.By using Abaqus/Explicit,dynamic explicit analysis was conducted.Stiffness reduction for the damaged elements was accomplished by the Vectorized User-Material(VUMAT)subroutine.Mises stress criterion was employed for the matrix and Puck criterion was employed for the fiber bunch.The damage process of tension and compression is simulated and the strength of 3D nonorthogonal woven composite was gained.