Investigation Of Mechanical Properties Of Woven Composites Considering Shear Pre-deformation

It has become a trend to use composite materials to manufacture advanced aeroengine fan blades.The three-dimensional(3D)angle interlocking woven composite materials have become one of the preferred materials due to the high specific stiffness,high specific strength,excellent impact resistance,good fatigue resistance and excellent structural design flexibility.However,the aero-engines fan blades have complex bending-twisting shapes,which are difficult to fabricate directly through weaving molding process.Therefore,it usually needs to be loaded many times to change the shape to meet the requirements before curing.This kind of process will change the mechanical properties of the woven composites,but the variable mechanisms have not been revealed up to now owing to the complexity.In response to this urgent need,this paper has successively carried out the study on the predeformation behaviors of 3D angle interlocking woven fabrics under cyclic loading and the influence of shear pre-deformation on permeability,static and dynamic mechanical behaviors.Firstly,the uniaxial tensile experiment and frame shear experiment of the 3D angle interlocking woven fabric under cyclic loading are carried out.The tensile predeformation behaviors and shear pre-deformation behaviors of the 3D angle interlocking woven fabric are analyzed.The influence of shear pre-deformation on the permeability of 3D angle interlocking woven fabrics is further studied to facilitate the curing molding.Combined with the experimental results,numerical simulation is used to analyze the 3D angle interlocking woven fabric with several typical shear angles respectively.Based on the experimental results,an empirical formula for the permeability of the three-dimensional angle interlocking fabric under shear deformation is given,and the predicted results are in good agreement with the experimental results.Secondly,two different 3D angle interlocking woven composite panels without shear pre-deformation and shear pre-deformation(20? shear angle)are designed and prepared.Then,the uniaxial tensile and compression experiments under quasi-static loads are carried out to study the effects of shear pre-deformation on the warp stiffness and strength of the 3D angle interlocking woven composites.According to the macro and micro morphology of the specimen after failure,the influence of shear predeformation on the static failure modes of the 3D angle interlocking woven composite is discussed.In addition,combined with the strain field obtained by the threedimensional digital speckle strain measurement system(DIC),the failure process is analyzed to reveal the influence of shear pre-deformation on the failure mechanisms of 3D angle interlocking woven composites.Thirdly,the 3D angle interlocking woven composites non-orthogonal unit cell model considering shear pre-deformation is established,and periodic boundary conditions are applied.The parabolic yield criterion and the Puck criterion are utilized as the failure criterion of the matrix and fiber bundles,respectively.VUMAT subroutine used in conjunction with ABAQUS is developed to study the effects of shear pre-deformation on the longitudinal stiffness and strength of the 3D angle interlocking woven composites under uniaxial tension and uniaxial compression.The correctness of the numerical simulation method is verified by the experimental results.In addition,the finite element model is used to study the effects of shear angles on the stiffness and strength in warp and weft direction of 3D angle interlocking woven composite materials.Finally,the influence of shear pre-deformation on the impact resistance of 3D angle interlocking woven composites is studied.The drop hammer impact tests of 3D angle interlocking woven composites plates without shear pre-deformation and with20? shear pre-deformation are carried out.The effects of shear pre-deformation on the initial stiffness,maximum impact load and energy absorption rate of the two types of specimens are analyzed.By observing the impact morphology of the specimens’ surface,the effects of shear pre-deformation on the damage propagation direction and the dent depth of the specimen impact surface are analyzed.A theoretical analysis model considering damage energy dissipation is further established.The predicted variation trend of the maximum impact load is basically consistent with the experimental results.