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论文范文
1. Introduction The purpose of armor systems is preventing entry of bullets into the protected area. The armor to be used should be durable and easy to produce, use, and repair. The traditional method of armoring is the use of thick steel plates. However, multilayer armor was developed in decades and improved penetration resistance/weight ratio relative to steel. In multilayered armors, the outer ceramic layer deflects the bullets, the artificial fibers hold the bullet particles, and the metal part stops the bullets. This kind of armor systems significantly less weigh than one-layer solid steel armors providing equivalent protection [1]. Enhancing the ballistic resistance of armors by using composite materials is a generally accepted practice in armor design. In the past few decades, laminate armors have been investigated to achieve good durability and lightweight armors [2]. Kevlar and steel are commonly used materials in ballistic armor industry especially in structural armor types [3, 4]. Armor design is typically performed in two stages especially for those that contain multiple stacks for maximum efficacy. First steps of this stage are the armor design and selection of appropriate materials for the application and the threat under consideration. Second stage includes simulation and testing the structure which define the ballistic limits of the materials being used in designing the armor and total efficiency of the design [5]. According to EN 1063 Ballistic Standards in Table 1, there are different types of projectiles and testing conditions of the ballistic test. Tests are classified into levels listed from BR1 to BR7 based on the geometry, the tip shape, the shooting distance, the mass, the speed, and the material of the projectile. There are two major applications of ballistic armors, the body armor and the structure armors. In the battlefield, humans are usually encountered BR2 level of threat, while vehicles and buildings are encountered a higher level of threat. Material type, geometry, application, and working conditions are the key parameters of the armor design. In the simulation process, the modeling conditions of both target and projectile are playing an important role in the results. Meshing tool, mechanical properties, and physical properties of the materials and material modeling characterizing like the type of elasticity and failure conditions are the most important modeling conditions in ballistic armor simulation process [6, 7]. Commercial software tools like SolidWorks, CATIA V5, and Ansys design modeler are commonly used to model the geometry of both armor and projectile. While tools like ABAQUS, Ansys with LS-DYNA, and AUTODYN 3D are used for material and test modeling [8, 9]. In this study, composite-layered laminate armor structures were designed, and test samples were manufactured. Simulations, as well as experimental tests at BR2 ballistic level, were performed, and results are presented. 2. Experimental Conditions and Results 2.1. Armor Structure The composite structures consisted of layers of Kevlar 29 fabric of 200 g/m2, 1 mm, 1.5 mm, or 3 mm thick S235JR metal sheets and a fiber-cement layer. HEXION MGS L285 resin impregnated with MGS H160 hardener was used for bonding the materials assembly. The damage in composite laminates at BR2 level ballistic impact with shear wave velocity in the target of 2 mm/µsec is localized within a zone of 3–10 cm near the impact area; therefore, samples with 10 cm × 10 cm were found to be sufficient to test the ballistic behavior of the laminate structure [10]. The samples were performed by pressing with 10–20 bar pressure at 60°C for 10 minutes with a hydraulic press. The structure has a targeted special design of fiber-cement board bonded to a steel plate via Kevlar, and an optimization study was carried out. The composite laminates were produced for add-on armored protection in prefabricated structures or buildings where the fiber-cement layer plays as a front layer which look alike the structure wanted to be protected, Kevlar layer as an aid layer to slow down the bullet, and steel layer to stop the bullet. Add-on systems will make it easier to repair structures in areas under attack. Only deformed plates will be removed and replaced with new ones. To provide protection with the cheapest and most common materials in the market, S235JR steel sheets, Kevlar 29, cellulose fibers, and fiber-cement were preferred. It was aimed to provide maximum protection at BR2 level with minimum weight, so fiber-cement and Kevlar fabrics were kept same for all samples and minimum metal sheet thickness for maximum protection was tried to be found. 
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