Multi-scale Study On Low-velocity Impact Of Plain Woven And Twill Woven Composites Based On Local Homogenization

The internal structure of plain weave and twill weave composites will be damaged under low energy impact load,which will negatively affect the overall properties of the composites.Furthermore,plain weave and twill weave structures have different properties under the same load due to different interlacing modes of fiber bundles.Besides,the plain and twill woven fabrics have intricate construction,so it is difficult to describe the damage failure behavior of plain weave and twill weave composites by a single scale model.Therefore,a multi-scale framework including micro,micro and macro is constructed in this paper to explore the low-speed impact response of plain weave and twill weave composites.The damage evolution process of each component,the overall stress-strain response of the single cell and the damage rate of the matrix under six kinds of displacement loads were discussed.The equivalent properties of the predicted fiber bundles were compared and analyzed with the values calculated by the formula method.On mesoscopic scale plain and twill in mesoscopic unit cell model is established,plain and twill mesoscopic unit cell is studied in the warp tension and compression,surface under the action of an internal and external shear damage extension situation,macroscopic stress-strain curve and the damage rate of each composition,and by means of experiment for verified the mesoscopic unit cell model.Finally,the meso-model of plain grain and twill grain is transformed into ECPL(Equivalent cross-ply laminate)model by means of local homogenization,and the Equivalent performance parameters of ECPL model of plain grain and twill grain are analyzed and compared.Then extends plain and twill ECPL model into macro lowspeed impact model,the model compared with the whole homogenization model retains the plain and twill weave structure characteristics,and then write the VUMAT subroutine to realize macroscopic model under different impact energy of the finite element simulation,through the formation of drop hammer impact at low speed experiment platform on macroeconomic model to verify the feasibility,The impact responses of the two models under different impact energies are analyzed and compared,and the damage of each layer under impact of the macro model is also explored.The final analysis and comparison results show that the longitudinal failure strength and inplane shear strength of the twill meridional equivalent layer are higher than those of the plain meridional equivalent layer,while the transverse strength and out-of-plane shear strength of the two layers are similar.When the impact energy increases gradually,the impact damage morphology changes from zigzag to cross,and the peak of impact force,absorption energy and delamination damage of twill braided composites are higher than those of plain braided composites at 5J and 7J impact energy.In the finite element results of the macroscopic model,the closer the monolayer is to the back of impact,the more fiber tensile and matrix tensile damage elements are generated,while the closer the monolayer is to the front of impact,the more matrix compression elements are generated.