Research Of Mesoscopic Structure And Elastic Properties Of2.5D Carbon/Epoxy Woven Composites

In the current environment of rapid growth of aerospace industry, aerospacestructures of short cycle, low cost and cost-effective are most welcome.2.5Dwoven composite is very potential, which can effectively avoid the poorperformance between layers of2D fabrics and the insufficiency of3D braidedcomposite in producing heteromorphic structure. Reducing manufacturing cost,shorten the production cycle and easy to prepare the rotary components are aswell their advantages. But the current research on the mechanical properties ofthis material is still rare. Research on the properties of shear and torsion,together with the damage and destruction properties and behavior under dynamicimpact loading is quite few. Coupled with the inhomogeneity, anisotropy andinevitable presence of internal cracks, voids and interface defects in braidedcomposites, which will complicate the damage evolution and growth behavior.So it's very urgent for us to start from the study mechanical properties of the2.5D woven composites, to the comprehensive study of stiffness, strength,residual strength and stability after damage in microscopic view. Therefore, thispaper focuses on the research of microstructure and elastic properties of2.5Dwoven carbon/epoxy composites by means of experimental and numericalmethods.Firstly, the mechanical properties of2.5D woven composites under tensile,compression and shear load have been investigated by using experimentalmethod with different specimen size and different loading direction. Theprincipal mechanical properties under those loads are obtained by experiment. Inaddition, the influence of the size effect on the material properties and failuremodes of the kinds of materials are analyzed.Secondly, the microstructure of2.5D woven composites are investigated.Different weave of idealized geometry microstructure are modeled and comparedwith those of the actual woven composites, which are produced by RTM process.The effects of weaving parameters (which including braiding angle, bypass,tortuous and cross-section area of yarns and fiber volume fraction) on themechanical properties of2.5D woven composites. Finally, take the warp enhanced.2.5D carbon/epoxy woven composite forexample, the elastic properties of this material are investigated by using finiteelement software ABAQUS. Mechanical responses of warp enhanced2.5Dwoven composites are simulated under different loading to obtain therelationship of stress and strain, from which the modulus and Poison' ratios canbe predicted. Theoretical and numerical results are compared with experimentaldata and the reasons of error are analyzed.