Study On Macro-Meso Modeling Method Of 3D Woven Composites Under High Speed Impact

Three-dimensional woven composites have been reported to have superior fracture toughness,fatigue life and damage tolerance compared with laminated composites due to throughthickness reinforcement.These properties make them lighter replacements for traditional highstrength metals and laminated composites.Therefore,they have been widely used in aerospace,automobile manufacturing,protection engineering etc.Although some research have been done on the mechanical properties in a multi-scale framework,there is still a lack of systematic and indepth study on the dynamic response of the composite material under high-speed,high-energy and complex impact loads and its damage and failure mechanisms.In this dissertation,the impact resistance study of the three-dimensional orthogonal woven carbon fiber/bismaleimide composites was carried out through the combination research of material mechanical performance test,multi-scale modeling method,finite element numerical simulation analysis,ballistic impact test and spinning impact tests.The main carried-out work are as follows:(1)Study of mechanical properties of bismaleimide and three-dimensional orthogonal woven carbon fiber/resin matrix composites.For pure resin and composite materials,quasi-static tension/compression/shear tests were carried out,and the failure and damage modes of the materials under different loads and the mechanical parameters were obtained,which provided necessary data for multi-scale numerical simulation analysis.In order to study the strain rate effect of materials under dynamic load,the Hopkinson bar test technique was used to carry out dynamic tensile and compression tests.It was found that both resin and composite materials have obvious strain rate effects,and the strength was more sentitive to strain rate,compared with modulus.The tensile strength of the resin increases first and then decreases as the strain rate increases.Under dynamic compression,the resin would undergo four stages: compression yield,strain softening,strain strengthening and abrupt rupture.As the strain rate increased,its yield strength gradually went down,and the ultimate failure strength first increases and then decreases.In the measured strain rate range of the composite material,the tensile strength in the warp and weft directions gradually increases with the increase in the strain rate,and the compressive strength in the warp,weft and thickness directions first increases and then decreases with the increase in the strain rate.(2)Research on the multi-scale modeling method of 3D orthogonal woven composite materials.As an important component of composite materials,resin was modeled with the Modified Bodner Partom constitutive model.The hydrostatic stress effect was considered in the model,which can effectively characterize the mechanical response of resin materials at low,medium and high strain rates.Based on the generalized unit cell method on the micro scale,MAC/GMC micromechanics analysis tools were used to predict the stiffness and strength of the unidirectional fiber bundles,and provide material parameters for the yarns in the mesoscale modeling.According to the composites yarn(warp yarn,weft yarn and binder yarn)system,determining the fiber volume ratio,and periodic boundary conditions,a meso-scale model including yarn and resin matrix that can reflect the complex fabric structure in the material was also established.The top-down method determines the strength in the yarn,and the tiebreak contact algorithm based on the cohesion zone method to simulate the bilinear traction separation law on the interface.Finally,a macro-scale model was established,assuming that the composite material was niform continuous material,and examining its averaged mechanical response,it has the highest computational efficiency.(3)Research on the macro-meso combined multiscale modeling method.Based on the idea of submodeling analysis technology,combined with the interface analysis in LS-DYNA,the macro-scale model is used in the global model,and the mesoscale used in the submodel,which realise a macro-meso combined multiscale modeling method.This method combines the advantages of the two modeling methods,which can not only achieve higher computing efficiency,but also finely represent the local damage of the material.The two different interface connection technologies of surface and node were compared.The selection principle of submodel size was discussed,and the effectiveness of the combined multiscale modeling method was verified through the examples of quasi-static tensile and dynamic impact simulation.(4)Study of the impact resistance of 3D orthogonal woven composites by ballistic impact tests and spinning impact tests along with numerical simulation.Ballistic impact tests were conducted using the gas gun technique with the composites impacted target and the cylindrical titanium projectile.The projectile velocity ranged from 180 m/s to 280 m/s,which amounted to320 J to 774 J impact energy,generating different results from rebound to embeded to perforation.Combined with numerical simulation,it was found that when the target was not peforated,the large deformation and vibration of the plate were the main energy absorption mechanism,and when the target plate was peforated,the deformation outside the structure decreases,and the local fiber shear failure and tensile fracture failure are the main energy absorption mechanisms.The spinning impact tests were carried out on the high-speed spin tester.For the application of the macro and meso combination modeling method,it wan found that the macro and meso combination modeling method can capture the characteristic effects such as large deformation and vibration in the impact process,and also predict the detail damage and failure behavior in local area.The wedge-shaped simulated blade impacted the cylindrical composite case at a speed of15000r/min?25000r/min(equivalent to an impact energy of 2400J?7300J),and obtained uncontained,critical contained and contained results.As a result,it was found that the energy absorbed by the composite case increased as the impact energy of the blade increased.Combined with numerical simulation analysis,the impact process of the high-speed rotating blade and the composite casingwas studied in detail.It was pointed out that the smaller impact angle,the asymmetry structural response of the casing and the existence of multiple impact points made the composite casing involve more area to participate in the absorption of blade kinetic energy through deformation,damage and failure.To sum up,this paper established a reliable mechanical performance characterization method and a macro-meso combined modeling method under a multi-scale framework for advanced threedimensional woven structural composite materials.Study of the structural dynamic response under high-speed and high-energy impact loads were carried out.The impact resistance of materials was evaluated from multiple perspectives.The work of the paper was of great significance for the application of three-dimensional woven composites to high-performance aero engines.