Numerical Simulation Of Mesomechanics Properties Of Three-dimensional Woven Composites

Three dimensional(3D)woven composites are fiber-reinforced composites.The fibers are the main part to bear loads,and the matrix plays the role of protecting fibers,preventing yarns from slipping and transferring loads.The advantages of 3D woven composites are high specific strength,good corrosion resistance,great damage resistance,etc.Compared to laminated composites that have the defects of poor impact resistance and delamination in the thickness direction,3D woven composites have excellent anti-penetration performance,which have an extensive application prosperity in the fields of aerospace,structure protection,etc.However,because of high test cost and long test period of 3D woven composite,mesoscopic solid models for 3D woven composites are often established at present to predict macroscopic mechanical properties of 3D woven composites with different technological parameters by numerical simulation while basic mechanical properties of fibers and matrix are known.In order to accurately predict the macroscopic mechanical properties of 3D woven composites,considering surface and interior regions influence the mechanical properties of3 D woven composites,the numerical simulation for 3D angle-interlock woven composites is carried out and the main research contents and results are as follows:(1)By Micro-CT images,based on reasonable assumption of yarn cross-section shape and yarn paths,through the textile modeling software Tex Gen,parameter modeling for 3D woven composites mesoscopic solid models is implemented,and 3D woven composites mesoscopic solid models with and without filling yarn are built respectively.According to the mesoscopic structural characteristics of the 3D woven composites,the composites could be divided into the interior region and the surface region,from which the representative volume units(i.e.,interior unit-cell and surface unit-cell)are extracted respectively.The surface unit-cell models are modeled by combination of two surface unit-cells.Hexahedral meshes are used to discretize the representative volume units,and periodic boundary conditions are applied to them.(2)Based on the interior and combination surface unit-cells models,the macroscopic elastic constants of 3D woven composites are predicted through numerical analysis.The results are compared with the experimental results,and the yarn deformation and stress distribution in the interior unit-cell under loads with different directions are discussed.The influences of variation of parameters(e.g.,yarn twist angle,fiber volume fraction,weft yarn spacing and the layer number of weft yarns)on the macroscopic elastic constants of composites are studied.(3)Damage models of each constituent of composites are established,which would be added into a user-defined material subroutine(UMAT)in finite element analysis software ABAQUS.Progressive damage numerical analysis for interior and combination surface unit-cells models of 3D angle-interlock carbon fiber/epoxy woven composites is performed respectively,and uniaxial tensile strength of composites in the warp and weft direction is predicted by means of volume weighted average method,which would be compared with the experimental results.Progressive damage process of composites is studied by observing the distribution of elements with the same damage modes during the load process,and the effects of variation of parameters(e.g.,yarn twist angle and weft yarn spacing)on the uniaxial tensile strength for 3D woven composites are investigated.