Microstructure Modeling And Mechanical Properties Analysis Of 3D Braided Composites

In recent years,the field of engineering has developed rapidly,and various advanced technologies are gradually being promoted and used in this field,with the consequent demand for various high-performance materials becoming more and more urgent.With the advantages of high specific strength,high specific modulus,impact resistance,fatigue resistance,good structural integrity and designability,3D woven composites have become important structural materials for aerospace,transportation and deep-sea fields.As it is widely used,the study of its mechanical properties has become a hot issue.In this paper,for three-dimensional woven composites,the detailed analysis of the fine structure of three-dimensional woven composites,the relationship between the fiber bundle direction cosine and the weave process parameters and geometric parameters are obtained,the mechanical properties of three-dimensional woven composites are predicted by substituting into the stiffness volume averaging method,and the mechanical properties of periodic composites are predicted by using the homogenization method.The main work is as follows:1.A three-single-cell model of three-dimensional four-way woven composites is studied.Based on the assumption of two straight-line segments and four straight-line segments fitting the directional helix of the fibre bundles of the face cell and the corner cell,the various spatial directions of the fibre bundles in the single-cell 45 ° division method and the horizontal division method are comprehensively analysed,and the detailed fibre bundle directional cosines of the three-single-cell are obtained.The advantages and disadvantages of the two division schemes are also analysed.2.The relationship between the weaving process parameters and the geometrical parameters of the single-cell model is derived analytically for the three shapes of fibre bundle cross-sections,and the weaving process parameters are used as initial parameters for the quantitative characterisation of the single-cell structure,and the calculation methods of fibre bundle volume fraction and yarn filling factor are obtained.3.The stiffness volume averaging method is used to predict the mechanical properties of3 D woven composites.The correctness of the above obtained expressions for the directional cosine and fibre bundle volume fraction is verified.The relationship between the elastic constants and the fibre volume fraction and braiding angle was quantitatively analysed in a single variable,and the effect of fibre volume fraction and braiding angle on the mechanical properties of 3D braided composites was obtained.4.The homogenisation theory is used to predict the mechanical properties of periodic composites.For unidirectional fibre composites,the homogenisation theory predicts the mechanical properties and compares them with the results of "Cheng Gengdong’s solution",and for reinforced concrete,the homogenisation theory predicts the mechanical properties and compares them with the results of the homogenisation module of ANSYS WORKBENCH to verify the correctness of the homogenisation procedure in this paper.