| Currently, the study of body armor projectile impact has a broad application value, because it has important reference values for the understanding of the failure mechanism and process of body armor. Besides, it can help to improve ways of weaving the material. But the impact process between the projectile and body armor is very short, and the whole process contains many issues such as material nonlinearity, large deformation and high strain rate impact. Note that it is very difficult to obtain deformation, stress, velocity, and energy in the impact experiment accurately. Therefore, numerical simulation has become an important method to study such transient dynamic impact problem.For a long time, researchers often use a simple plane to modeling the body armor. The viscoelastic property of body armor which is made of high polymer aramid fiber material is often overlooked, and the fibrous constitutive formula of the material is often lack of understanding. It is also unknown about the detail processes of the projectile and fabric contact. Moreover, the processes of microscopic damage mechanism of material are utterly unknown. This property might lead to a low accuracy in numerical simulation. In order to meet the demands of accuracy and efficiency, it must make some attempts to overcome these difficulties.In this paper, based on a number of studies of relevant research about composite armor materials, structural characteristics and finite element modeling, we investigate four different numerical models. By testing projectile velocity, kinetic energy, maximum displacement and Von Mises equivalent stress of the fabric under projectile impact, using the Lambert-Jonas equation,we compare the computational accuracy and efficiency of simple flat model and the weaven model of a single layer Twaron material. Based on the advantages and disadvantages of these two modeling methods, we propose a new way to optimize the modeling method, and then test the new hybrid model through simulations. Here are the main contents of this paper:(1) The development of composite armor materials, bullet proof mechanism, constitutive model of Twaron materials and ballistic experiments of Twaron materials are firstly introduced and discussed. With the application of HyperWorks finite element analysis software, we construct the finite element model of the traditional flat fabric and three-dimensional weaven fabric with Belytschko-Tsay shell elements, the processes include meshing, adding contact, loading and boundary conditions. Computed on LS-DYNA platform and then compare the numerical results with the experimental data, we get to reveal the microscopic processes of fabric damage mechanisms.(2) With a comparative analysis of the two different modeling methods, we propose a hybrid cross section fabric modeling method for a nearly realistic computational simulation. It can not only predict the failure mechanism of the fabric accurately but also save computing time. This provides a reference and theoretical basis for the future study of related issues.(3) On the basis of simulations of flat and weaven fabric, a triaxially braided Twaron fabric is studied. The inclination angle of oblique yarn has a great effect on the fabric properties, so the degree of30,45and60are analyzed and compared in the simulations, we have studied the stress changes of the fabric with different boundary conditions. It provides certain help for the future research of bullet proof vest. |
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