Research On Low-velocity Impact Damage Of Plain Woven Composites Based On Multi-scale Method

Plain woven composites are widely used in aerospace,automobile industry,sports and medical fields because of their excellent in-plane properties and impact resistance.In the process of production and service,the woven structure will produce invisible damage under low-velocity impact.In addition,the complex internal structure of plain woven composites has significant heterogeneity and anisotropy.The traditional single scale models can not fully characterize the complex damage mechanism of plain woven composites.Therefore,in order to make clear the low-velocity impact damage mechanism of plain woven composites and to make better use of its excellent characteristics,this paper constructs a multi-scale modeling framework with three scales: microscale,mesoscale and macroscale,and studies the damage characteristics of plain woven composite laminates after low-velocity impact.Firstly,a microscale representative volume element(RVE)for fiber tows was established based on the assumption of staggered arrangement of fibers.The corresponding damage initiation and stiffness degradation criteria were applied to the fiber and matrix,respectively.The effects of fiber volume fraction on stiffness and strength of the fiber tows were discussed.Moreover,the progressive damage process of the microscale RVE model with fiber volume fraction of 80% under six typical displacement loads was analyzed.Secondly,a mesoscale RVE of the plain woven composites was established based on the 3D crimp model.Combining with the 3D Hashin failure criterion and the progressive damage criterion based on fracture energy,the stress-strain response and progressive damage process of the high-fidelity mesoscale model under tensile,compression,in-plane and out-of-plane shear loads were studied and compared with the experimental results.The global stress-strain response of high-fidelity mesoscale model under four loads were obtained,and the local homogenization method based on volume averaging method was used to transforms high-fidelity mesoscale model into the equivalent cross ply laminate(ECPL)model with 0° and 90° layers.The stress-strain response of ECPL mesoscale model under longitudinal tensile and compressive loading was studied respectively,and the progressive damage process was discussed.Finally,the ECPL mesoscale model was extended to a plain woven composite laminates on macroscale by array method,and the low-velocity impact damage of laminates under different impact energy was simulated with VUMAT user subroutine.A low-velocity impact test platform for plain woven composite laminates was built,and the accuracy of the finite element model was verified by experiments.On this basis,the low-velocity impact damage response of plain woven composite laminates under different impact energy was discussed.The results show that the intra-and inter-laminar damage area increase with the increasing impact energy.The most serious damage is in the back layers.The main failure modes are fiber tensile and matrix tensile damage,in which the fiber tensile damage mainly extends along the direction of 0° and 90°,while the matrix tensile damage is mainly rhombic distribution.The interface delamination failure is more serious in the middle layers,and the shape of the delamination area is mainly cross-shaped during the low energy impact,and changes to the diamond shape with the increase of the impact energy.