弹道防护用先进复合材料弹道响应的研究进展

本文对弹道防护用先进复合材料的弹道响应研究及其在工程领域的应用现状进行了综述。首先,基于工程应用研究的试验结果,对超高分子量聚乙烯(UHMWPE)纤维、对位芳香族聚酰胺(PPTA)纤维、芳Ⅲ纤维、聚对苯撑苯并双噁唑(PBO)纤维和聚酰亚胺(PI)纤维等高性能纤维的防弹性能及其复合材料在弹道防护工程领域的应用现状进行了概述,近年来先进复合材料的防弹性能随着纤维力学性能的突破而逐渐提高;其次,讨论了先进复合材料弹道响应的影响因素及其作用机制,发现先进复合材料的塑性拉伸变形是其抵挡弹丸侵彻的主要防弹机制;最后,对弹道防护用先进复合材料的研究方向进行了展望。      

Analysis of failure of add-on armour for vehicle protection against ballistic impact

The deployment of peacekeeping forces in conflict areas has shown that some armour systems are not sufficient to meet the latest threats.This applies particularly to lightweight vehicles whose armours give protection only against low calibre ammunitions.The development, production and fielding of add-on armours gives the answers to the demand for mission adjustable protection systems.Add-on armours represent a new protection philosophy, because they are produced as a separate kit, designed to achieve different protection levels. They have several advantages: Separate transport of armour and vehicle, they can be screwed to the main skull structure by crews and they are easily repairable or upgraded.Advanced add-on armours are produced by a clever combination of ceramic tiles backed by metal or composite plates.The utilization of advanced ceramics began in the 1960s when the US Army was demanding lightweight body armours for helicopter crews. Nowadays a wide spectrum of advanced ceramics is currently used for armour production, including alumina, silicon carbide, titanium diboride and boron carbide.Ceramics possess a high protection potential due a moderate density combined to a high compressive strength. But they are too brittle to be used without a ductile material backing.The design of ceramic add-on armours is a difficult task due to the high number of parameters involved: material selection, thicknesses of different materials, impact obliquity, etc. A design based exclusively on experimental tests is therefore expensive in money and time.This paper summarizes the utilization of analytical and numerical computation of ceramic/metal and ceramic/composite add-on armour failure process as valuable tools for armour design optimisation. Some examples are presented showing a good agreement between analytical, numerical and experimental results of residual mass and residual velocity of kinetic energy projectiles after perforation of the add-on armour.     

Hybrid nonlinear surrogate models for fracture behavior of polymeric nanocomposites

We present a hybrid nonlinear surrogate model for fracture in polymeric nanocomposites. The phase field method is employed to model fracture in the polymer matrix. Since the stochastic analysis on the output of the mechanical model is prohibitively expensive, surrogate models (SM) are very attractive alternatives. In order to get an optimal and robust solution, we propose a hybrid nonlinear surrogate model (HSM) for the prediction of the fracture toughness of PNC. It is constructed with the use of the polynomial regression and the Kriging interpolation. The support data for such HSM is generated by a phase-field model for brittle fracture with six chosen input parameters. The validation of the surrogate model and by this its qualitative assessment is done based on a scanning test set algorithm. The constructed and assessed HSM is then used to present the behavior of fracture toughness of PNC with respect to various input parameters with very low computational costs and high accuracy. Within the domain of interest, the analysis shows that Young’s modulus of the matrix has no optimum value, in which, the higher input value causes higher response. On the other hand the volume fraction of clay platelets at about 5% showed stability of the response, in which, the higher input value leads to no change in the response.     

仿生柔性防护装具的设计及防弹性能测试

依据仿生学原理,借鉴硬骨鱼鳞的微观结构及叠加模式,设计并制备了6套仿生柔性防护装具。使用了两种复合鳞片,分别为SiC陶瓷-超高分子量聚乙烯(UHMWPE)复合防护鳞片和Al₂O₃陶瓷-UHMWPE复合防护鳞片。对柔性防护装具进行侵彻测试,分析了复合鳞片类型、覆盖角度和子弹侵彻位置对柔性鳞片防护装具防弹性能的影响。结果表明,新型柔性鳞片状防护装具均能成功抵挡速度为(445±10) m/s的手枪弹(铅芯)侵彻,垫层材料的凹陷深度为5~20 mm。SiC-UHMWPE复合鳞片防护装具的防弹性能显著优于Al₂O₃-UHMWPE复合鳞片防护装具。此外,柔性防护装具的防弹性能均随着鳞片覆盖率的增加而提高。本研究成果为新型柔性防护装具的设计提供理论依据和科学指导。      

Creep forming of high strength polyethylene fiber prepregs for the production of ballistic protection helmets

Production of highly three dimensionally curved composite products with continuous fibers so far is dependent on drapability of the fibrous precursor. Drapability depends on the in-plane shear compliance of the precursor and on its bending flexibility. Elongation of the fibers usually gives a negligible contribution to drapability because high performance fibers typically show small elongations to failure. However, high strength polyethylene fibers are an exception. They may accumulate considerable creep elongation, provided that the loading time is sufficiently long. Choosing a proper processing temperature, somewhat below the melting temperature, allows that this sufficiently long processing time is still within the limits that are acceptable for industrial production. This paper explores the technique for creep forming of high strength polyethylene fiber prepregs for the production of full scale ballistic protection helmet shells. Such helmets show a highly three dimensionally curvature. It was found that such helmets can be made by creep-forming indeed. The helmets were free of wrinkles and showed excellent protection against supersonic projectiles. It was found to be very important that a homogeneous temperature distribution is provided during creep forming. Very high fiber tensile stresses occur during creep forming. Control of these high creep stresses is necessary.     

Hybrid nanocomposites based on polystyrene and a reactive organophilic clay

The preparation of new hybrid nanocomposites, by emulsion polymerization of styrene in the presence of a reactive organophilic clay, and their characterization are described. The reactive organophilic clay is synthesized by exchanging the inorganic cations in the interlayer structure of a natural clay with the quaternary salt of the aminomethylstyrene. This salt is prepared by a Gabriel reaction starting from the (chloromethyl)styrene. The polymeric matrix of the resulting materials was found to be constituted by polystyrene homopolymer and by a blocky copolymer of styrene and quaternary salt of the (aminomethyl)styrene units. The glass transition temperature of the nanocomposites increase as the percentage of organophilic clay increases, although the average molar masses of the polymeric matrix decrease, because of termination and/or chain-transfer reactions caused by the organophilic clay during the polymerization. Accordingly, the inherent reinforcing action due to the presence of the reactive organophilic clay is higher than the observed one.     

Double corrosion protection mechanism of molybdate-doped polypyrrole/montmorillonite nanocomposites

Nanocomposites based on polypyrrole (PPy) doped with molybdate (PPy(MoO₄)) and montmorillonite (MMT) were prepared by chemical polymerisation. The morphology of nanocomposite particles was studied by scanning electron microscopy. The chemical structure of conducting polymers (CPs) in nanocomposites was characterised by Raman spectroscopy. The thermal analysis showed that all CPs in the nanocomposites were stable for more than 500°C. Energy diffraction X-ray showed that the amount of Mo in element the PPy(MoO₄)/MMT nanocomposite was 5.55%. The corrosion protection mechanism of the nanocomposites was investigated by electrochemical methods, showing that MMT acted as a barrier layer in nanocomposite and molybdate as an inhibitor for corrosion protection of metal.     

Facial fracture protection criteria for the Hybrid III load sensing face

A method for establishing protection criteria for the Hybrid III load sensing face has been developed. Impactor PMTO (Post Mortem Test Object) tests described by Welbourne, Ramet, and Zabreski (1989) were repeated with a Hybrid III dummy equipped with the load sensing face. The probability function for PMTO nasal fracture based on energy was used as a basis to determine protection criteria for nasal fracture measured by the load sensing face.     

Corrosion-resistant polypyrrole-banana carbon (PPy-BC) nanocomposites for protection against electromagnetic interference: a green approach

Journal of Materials Science: Materials in Electronics - The article focuses on the suitability of electrically characterized polypyrrole-banana carbon (PPy-BC) nanocomposites for broadband...     

Hybrid titanium dioxide/PS-b-PEO block copolymer nanocomposites based on sol-gel synthesis

The poly(styrene)-b-poly(ethylene oxide) (SEO) amphiphilic block copolymer, with two different molecular weights, has been used as a structure directing agent for generating nanocomposites of TiO(2)/SEO via the sol-gel process. SEO amphiphilic block copolymers are designed with a hydrophilic PEO-block which can interact with inorganic molecules, as well as a hydrophobic PS-block which builds the matrix. The addition of different amounts of sol-gel provokes strong variations in the self-assembled morphology of TiO(2)/SEO nanocomposites with respect to the neat block copolymer. As confirmed by atomic force microscopy (AFM), TiO(2)/PEO-block micelles get closer, forming well-ordered spherical domains, in which TiO(2) nanoparticles constitute the core surrounded by a corona of PEO-blocks. Moreover, for 20?vol% sol-gel the generated morphology changes to a hexagonally ordered structure for both block copolymers. The cylindrical structure of these nanocomposites has been confirmed by the two-dimensional Fourier transform power spectrum of the corresponding AFM height images. Affinity between titanium dioxide precursor and PEO-block of SEO allows us to generate hybrid inorganic/organic nanocomposites, which retain the optical properties of TiO(2), as evaluated by UV-vis spectroscopy.     

A method for scaling ballistic penetration phenomena

There are several established formulae for projectile penetration into semi-infinite concrete targets. Most of them include a term which indicates that regular scaling does not hold in this situation. Most of these formulae were derived using curve-fitting procedures, so that these terms do not represent any physical meaning. Non-scaling is also found in long rod penetrations, which cannot be attributed to strain rate effects. It is suggested here to differentiate the energy spent by the projectile during the penetration process into two parts, one—the energy expended for surface effects and the other—the energy expended for volume effects. By doing so, it is possible to derive expressions which account for the irregularity in scaling. These expressions are derived from the global, energy balance point of view, so they do not require the detailed characterization of the materials involved. They only require strict adherence to replica scaling procedures.

A similar approach is used to account for strain rate effects, but in that case, the results are not as general and can be applied only to a narrow span of configurations. Examples are cited from tests with concrete penetration and long rod penetration into different targets.     

Epitaxial Ni films for ballistic ferromagnetic nanostructures

Nickel films of 170 nm thick were grown on sapphire substrates of the A, R and C orientations. Their electric characteristics and surface morphology were studied. Peculiarities of the film growth and optimum growth conditions for films of high electron mobility were determined. Nickel films grown on the sapphire A-plane with a high residual electron mean free path were found suitable for the fabrication of ballistic planar ferromagnetic nanostructures. Ballistic electron transport was observed in cross-type epitaxial Ni (111) nanostructures.     

High-frequency performance projections for ballistic carbon-nanotube transistors

A quasi-static approach is combined with a theory of ballistic nanotransistors to assess the high-frequency performance potential of carbon-nanotube field-effect transistors. A simple equivalent circuit, which applies in the ballistic limit of operation, is developed for the intrinsic device, and then employed to determine the behavior of the unity-current-gain frequency (f/sub T/) with gate voltage. The circuit is shown to reduce to the expected forms in the so-called "MOS" and "bipolar" limits. The f/sub T/ is shown to approach a maximum value of v/sub F//2/spl pi/L/spl ap/130 GHz/L (/spl mu/m) at high gate voltage, where v/sub F/ is the nanotube's Fermi velocity and L is the channel length, and to fall at low gate voltage due to the presence of source and drain electrostatic capacitances. The impact of the gate electrostatic capacitance on the f/sub T/ is also discussed. Numerical simulations on a "MOSFET-like" or "bulk-switched" carbon-nanotube transistor are shown to support the conclusions.     

Models for the ballistic impact of fabric armour

Two types of model are applied in this paper to model homogeneous and hybrid fabric armour panels. The first model uses the direct-step finite element method to predict the ballistic properties of fabric armour while the second model is analytical. Output from the two models is compared with experimental data and the analytical model is shown to be a useful means for rapidly assessing new armour designs.     

A simple ballistic material model for soda-lime glass

Various open-literature experimental findings pertaining to the ballistic behavior of glass are used to construct a simple, physically based, high strain-rate, high-pressure, large-strain constitutive model for this material. The basic components of the model are constructed in such a way that the model is suitable for direct incorporation into standard commercial transient non-linear dynamics finite-element based software packages like ANSYS/Autodyn [ANSYS/Autodyn version 11.0, User documentation, Century Dynamics Inc. a subsidiary of ANSYS Inc.; 2007.] or ABAQUS/Explicit [ABAQUS version 6.7, User documentation, Dessault systems, 2007.]. To validate the material model, a set of finite element analyses of the Edge-on-Impact (EOI) tests is carried out and the results compared with their experimental counterparts obtained in the recent work of Strassburger et al. [Strassburger E, Patel P, McCauley JW, Kovalchick C, Ramesh KT, Templeton DW. High-speed transmission shadowgraphic and dynamic photoelasticity study of stress wave and impact damage propagation in transparent materials and laminates using the edge-on impact method. In: Proceedings of the twenty-third international symposium on ballistics. Spain: April 2007, and Strassburger E, Patel P, McCauley W, Templeton DW. Visualization of wave propagation and impact damage in a polycrystalline transparent ceramic-AlON. In: Proceedings of the twenty-second international symposium on ballistics. Vancouver, Canada: November 2005.]. Overall, a good agreement is found between the computational and the experimental results pertaining to: (a) the front-shapes and propagation velocities of the longitudinal and transverse waves generated in the target during impact; (b) the front-shapes and propagation velocities of the “coherent-damage” zone (a zone surrounding the projectile/target contact surface which consists of numerous micron- and sub-micron-size cracks); and (c) the formation of “crack centers”, i.e. isolated cracks nucleated ahead of the advancing coherent-damage zone front. Relatively minor discrepancies between the computational and the experimental results are attributed to the effects of damage-promoting target-fixturing induced stresses and cutting/grinding-induced flaws located along the narrow faces of the target and the surrounding regions.     

Codesign for transitions governance: A mid-range pathway creation toolset for accelerating sociotechnical change

Vision building, pathway construction and experimentation are key processes in the management of long-term sociotechnical transitions. The need to accelerate transitions and to adapt transition management to new country contexts calls for new means to catalyse these processes. We improved the path creation toolsets and procedures of transition management to create more detailed pathways and analyses of pathway step interrelations. Our path creation system uses magnetic elements that could be easily moved around a large metallic board, a set of procedures and a digitalized counterpart of the board for out-of-the-workshop commentary and reporting. The system has facilitated and anchored well the discussions by participants with cross-sectoral backgrounds. Overall, the redesigned system underscores the potential that codesign for sustainability transitions holds.