Research On The Containment Of2D Carbon Fiber Triaxial Braided Tape Wound Composite Casing

Carbon fiber Reinforced composites have been widely used in aerospace field due to its advantages of high specific strength, high specific modulus and corrosion resistance. The GE company employs2D carbon fiber tri-axial braided composites in the fan containment system on the GEnx engine. The usage of composite enables GEnx engine reducing weight about160kg and passing the full engine test in July2007. The containment process of the aero-engine fan case is a typical non-ideal high speed impact process. Besides, the impact characteristics and dynamic responses of the composite casing are more complicated than the metal casing. Thus investigating on the composite fan casing systematically and thoroughly have great significane for its application on the commercial aircraft engine. In the current dissertation, the following issues were studied in terms of experiments, theoretical analysis and numerical simulations:(1) Investigation on the numerical simulation methods. Based on the commercial finite element codes ANSYS/LS-DYNA, the high velocity impact model of single layer and multi-layers triaxial braided composites were developed by virtue of three types of modeling methods, i.e. yarn model, unit cell model and continuum model. The numerical simulation results and the computation efficiency were compared for three methods. It is concluded that, the yarn model is efficient in predicting the fiber fracture failure, sliding and pull-out, but is difficult in modeling and cost greatly more computation time. The unit cell model and continuum model predicted similar failure modes-the cracking along the longitudinal and transverse direction. The unit cell model can describe the fiber orientation of braided fibers, thus is closer to the actual reinforced architecture. As the impact resistance performance and the computation efficiency predicted by the continuum model is very close to the unit cell model, but the continum model can be developed more convinently, and suitable for enginering application. In consequence, the continuum model was used in studying the high velocity impact response of composite casing.(2) Investigation on the ballistic impact properties of the2D triaxial braided composite. Ballistic tests were conducted with the titanium flat-ended cylinder projectile and the rectangular blade-like projectile to evaluate the influences of the projectile shape on the test results. To figure out the influences of the carbon fiber reinforcement architecture on the ballistic performace, one type of satin woven laminated composites were also used in comparison tests. Based on the failure modes and damage area shape observed in tests, the Lopez-Puente model were modified, and the energy differential equation with repect to projectile displacement were established. The theoretical model was validated by predicting the ballistic limit correctly. In addition, the numerical model employing the CDM material model and continuum modeling method were used to study the impact process and the damage mechanism of the composite target.(3) Investigation on the containment mechanism of the2D triaxial braided composite casing. Component containment tests were conducted on the high speed rotating machninery for the composite casing using TC4titanium blade. Three typical results were obtained in the tests, including contained result, near critical contained result and uncontained result. The impact process between the blade and the composite casing was analyzed by the numerical simulation results in combination of test results. Three crutial influencing factors-casing thickness, blade kinetic energy and the impact angle were analyzed in detail by parametric study, which derived the empirical designing equations for composite casing.(4) Investigation on the engineering application of the2D triaxial braided composite casing on the large aircraft engine.The original titanium fan blade and stiffened casing were substituted for the composite fan blade and casing to improve the containment performance of the first stage fan containment system for a certain type aero-engine, and satisfy the demand of airworthiness regulation. A series of single blade and three blades containment finite element model were developed. The impact process between the composite fan blade and the braided compsite fan casing were analyzed, and the effects of the trailing blades on the containment process were also investigated. It is concluded that the using of the composite containment system can reduce weight of the aeroengine and improve the containment efficiency at the same time.