Research And Application On Numerical Simulation Method Of Kevlar Woven Fabric Subjected To Impact

Current containment practice on most aero-engine incorporates a thin metal facing backed up bylayers of unimpregnate composite fabrics. To further investigate the containment mechanism andfailure mode of the containment structure, constitutive model and numerical simulation method oftypical aramid fabrics subjected to ballistic impact as well as its application to fan case ispresented inthis study.(1)The equilibrium of the unit-cell and viscoelastic stress-strain relationship based onthree-element model is derived. Parameters of the material model are extracted from complexgeometry and existing tensile test data. A one-element test and ballistic impact simulation ofsingle-layer Kevlar fabric are used to verify the model can properly characterize tensile and ballisticimpact behavior of dry fabrics.(2)Ballistic impact tests of Kevlar49fabric warps with various fabric layers and initial wrappingtensions are performed by using flat blades as projectiles. Results show that fabric energy absorptionincreases slightly at the beginning and then decreases substantially with pre-tension. It is apparent thatenergy absorption capability of Kevlar49woven fabrics improves with number of fabric layers andrelationship between critical energy absorbed by fabrics and layer can be fit by a quadric equation.(3)Numerical simulation methodology with unit-cell based model is developed and verified byballistic impact results and the effect of mesh size and hourglass control types are examined. Besides,comparison between single fabric layer and multi-ply fabrics demonstrate that new layer-to-layerfrictional energy dissipation mechanism is added to multi-ply fabrics thus improving the energyabsorption capacity at post-impact stage.(4)The developed and validated numerical simulation analyses are used to discuss the trajectoryof released blade, interaction between released blade and containment case and failure mode ofcontainment case. Simulation revealed that while fabric warp provide the main containment capabilityfor released blade, the interaction between metal ring and fabrics as well as stiffness of metal ringshould also be considered during soft-wall containment design.Numerical simulation methodology with unit-cell based model vilified by ballistic impact resultscan be applied to soft-wall containment analyses, providing a potential tool for containment-relateddesign and certification.