Modelling Of 3D Orthogonal Woven Fabric Weaving Process And Investigation Of Compression Performance Of Its Reinforced Composite

Carbon reinforced composites gradually replace traditional metallic materials in the field of mechanical engineering for the high-end equipment because of its specific strength,specific modulus and other excellent performances.Among them,3D orthogonal woven fabric as a reinforcement can significantly improve the axial compression performance and compression after impact(CAI)of the composite.However,the fabric geometry is determined in weaving process by the tow tension which results in variety tow trajectories and irregular tow cross-sections.These differences of fabric micro-geometry further affect mechanical performance of the composite.Therefore,weaving process have a significant effect on the mechanical performance of composites.In this paper,the 3D orthogonal woven fabric weaving process and compression performance of its reinforced composite were studied.A home-made weaving loom for the 3D orthogonal woven fabric were designed and developed according to the weaving principle.A geometry model of 3D orthogonal woven fabric at fiber scale was build based on the dynamic method in which tow tension was considered.Furthermore,a finite element model of 3D orthogonal woven composite was generated depended on the fiber trajectories from the fabric geometry.Then,the validity of the finite element model was verified by the experiment results of axial compression tests and CAI tests.At last,the effects of tow tension in weaving process on the axial compression and CAI performance of 3D orthogonal woven composites were analyzed with simulations and experiments.The main research work is divided into the following chapters:(1)The weaving principle of 3D orthogonal woven fabric are analyzed.A home-made weaving loom is designed and developed based on the weaving principle and the fabric geometry characters.3D orthogonal woven fabrics with different tow tension configurations(N25,N50,N100)are obtain from the home-made loom.The effect of tow tension on the fabric geometry is analyzed.The results show that the Z-binder tow tension have significant effect on the micro-geometry of 3D orthogonal woven fabric.As the increase of Z-binder tow tension,the crimps of out-layer weft tows increased and Z-binder tow decreased.On the other side,the cross-section of warp tow from rectangle transforms to convex as increasing of Z-binder tow tension.(2)The weaving process of 3D orthogonal woven fabric is simulated at fiber scale by a numerical model which is based on the dynamic method and continuum mechanics.The influence of tow tension on the fabric micro-geometry during interweaving process of tows is analyzed.The results show that the lateral force from Z-binder tension is the cause of crimps of out-layer weft tows and the crimp increases as the increase of Z-binder tension.In addition,the weft tow crimps result in fiber waviness at edges of warp tow which is exhibited as tow twist and the twist angle increases as the increase of Z-binder tension.(3)Voxel mesh method and mesh recognized method are developed to transform the fiber scale geometry model of 3D orthogonal woven fabric to continuous solid model depend on the fiber trajectories.In addition,the fiber trajectories are also used to assign the local material orientation for each tow element.A periodic boundary condition is configured for the represent volume element(RVE)of composite along warp and weft directions.And then,based on constitutive law and failure criterion of heterogeneous material of the composite,a finite element model of the 3D orthogonal woven composite is built for the further study of mechanical performance of composite.(4)Optimization and adjustment are carried out for the dimensions of composite specimen according to the ASTM test standards and geometry characters of 3D orthogonal woven fabric.And then,axial compression test method and CAI test method are proposed and the corresponding test platforms are set up.(5)The axial compression tests are conducted and the validity of the finite element model is verified.The effect of tow tension on the compression performance of 3D orthogonal woven composite are analyzed.The results show that the crimps of weft tow which are caused by the Zbinder tension lead to the decrease of compression properties include modulus and strength along weft direction.On the other side,warp tow twist which is caused by the crimps of weft tow lead to the decrease of compression properties at warp direction.In addition,the experimental results of CAI test show that the crimps of out-layers weft tow lead to resin enrich on the fabric surface.This will further result in resin debond damage in a large area and then reduces the CAI performance of the 3D orthogonal woven composites.