Research On The Containment Of Soft Wall Casing Wrapped With Aramid Fiber Fabric

Soft wall casing wrapped with high-performance aramid fiber fabric is one of the typical light-weight composite casings of aero-engine.It has been widely used in the large civil turbofan engine due to its advantages of light weight,high specific strength,and excellent impact resistance.However,in our country,the research work about the containment of soft wall casing is very limited.In the current dissertation,the containment capability and design approach of soft wall casing wrapped with aramid fiber fabric were investigated through material mechanical test,numerical simulation and blade containment test.The following works were studied:(1)Investigation on mechanical properties high performance aramid fiber fabric.Quasi-static tension test,high strain rate tension test,picture frame shear test and friction test were conducted for the Kevlar and three other kinds of domestic aramid fiber materials(Taparan,F248,F368).Some practical and effective test methods for the aramid fiber fabric were developed.Large amount of material properties data was obtained through the tests.The material respose behaviors and properties under various loads were understood more deeply.It was discovered that,The tensile strength of F368 is the largest,the elastic modulus of Kevlar and F368 is larger,the strain rate effect of Kevlar is most obvious,the shear modulus of Kevlar and F368 is larger,and F368 has the greatest friction coefficient.(2)Investigation on numerical simulation method for the impact of high-performance aramid fiber plain-woven fabric.Based on the commercial finite element codes ANSYS/LS-DYNA,the yarn model and continuum model were established to represent the fabric under the impact of cylindrical projectile.The simulation results of single layer fabric,multi-layer fabric and different aramid fiber fabric were studied.The calculation precision and efficiency of the two modeling methods were compared.It is concluded that,the yarn model has a better prediction in the fiber fracture,sliding and pulling out,but is difficult in modeling and cost greatly more computation time.The continuum model can only show macroscopic damage and deformation of fabric,but it is similar to the yarn model in the overall deformation characteristic,damage evolution pattern and energy prediction.Moreover,the modeling of continuum model is simple and suitable for the practical engineering applications.In consequence,the continuum model was used in the numerical simulation of soft wall casing containment.(3)Investigation on containment mechanism and design approachs of soft wall casing wrapped with Kevlar fabric which is the most commonly used aramid fiber fabric.A series of small-scale and large-scale containment tests were conducted in the high speed spin tester.Several innovative key test technologies were developed.The influence of fabric layers number,blade-off speed,stiffness of inner metal ring and other kinds of factors were studied.The numerical simulation method of soft wall casing containment was also studied and developed.Combined with the experiments and simulations,the containment capability and characteristics of soft wall casing wrapped with Kevlar fabric were studied and discussed,including the containment process,the deformation of outer fabric,the effect of inner metal ring,etc.A design equation was derived to describe the relationship between the blade impact kinetic energy and the required Kevlar fabric thickness.It can be used to help in the design of soft wall casings for areo-engine designer.(4)Investigation on the engineering application of soft wall containment structure.A real TC4 fan casing was reinforced by wrapping multiple layers of Kevlar fabric,and two real fan casing containment tests and numerical simulation were conduted.The results verify the validity of the soft wall containment structure for the fan blade and further help to improve the containment design approach.Combining the casing containment test and numerical simulation,the containment capability and weight loss performance of soft wall casing and titanium alloy casing were compared.It is found that,the soft wall casing can reduce the weight and improve the efficiency of the containment system obviously.