芳纶Ⅲ无纬布在柔性防弹衣中的应用

为了研制轻量化、舒适以及人机工效性好的防弹织物，从提升柔性防弹衣的防弹性能入手，通过对2层芳纶Ⅲ无纬布靶板、4层芳纶Ⅲ无纬布靶板、芳纶Ⅲ机织物靶板、2层芳纶Ⅱ无纬布靶板和4层芳纶Ⅱ无纬布靶板5种防弹材料进行弹道冲击试验，从弹道极限V₅₀值、比吸能值、凹陷深度及弹着点形貌4个方面进行对比分析，在此基础上对4层芳纶Ⅲ无纬布靶板进行结构优化。结果表明：当面密度相近时，4层纤维铺层材料的防弹性能比2层纤维材料的好；4层芳纶Ⅲ无纬布靶板的防弹性能最好；无纬布在受到弹道冲击时应力集中显著，纤维以剪切断裂为主要损伤模式；机织物在受到弹道冲击时，主要以拉伸断裂为主要损伤模式；将芳纶Ⅲ机织物放置于靶板迎弹面一侧、4层芳纶Ⅲ无纬布放置于贴身面一侧的结构有利于提升复合型防弹材料的防弹性能；当芳纶Ⅲ机织物与4层芳纶Ⅲ无纬布的质量比为1∶3时，其防弹性能最好。     

双等离子体改性超高分子量聚乙烯复合材料的弹道响应

为揭示双等离子体改性对超高分子量聚乙烯(UHMWPE)复合材料冲击性能的影响,采用真空辅助树脂灌注成型技术(VARI)制成UHMWPE复合材料,借助原子力显微镜等手段对改性前后的纤维表面进行观测,探究复合材料在低速及高速冲击时的抗冲击性能以及防弹机制。低速冲击载荷作为响应值构筑响应曲面模型,高速摄影机捕捉子弹侵彻改性前后复合材料的过程,分析板材的吸能情况并对侵彻后的试样进行表面观测。结果表明：未改性板材通过各层振荡式波动以形成严重分层来耗散能量;改性后的材料能有效地包覆住子弹,背弹面表层纤维呈现原纤化,断口处出现树脂大量富集,阻抗作用增强,吸能值较未改性材料提高45.59%。     

超高分子量聚乙烯织物/聚脲柔性复合材料的抗破片侵彻机制

为研究平纹机织叠层和三维角联锁增强聚脲柔性复合材料的抗侵彻性能，以15 mm角联锁整体织物及叠层平纹织物(单层厚度0.39 mm, 40层)为研究对象，通过表面喷涂聚脲制备2种不同织物结构的超高分子量聚乙烯(UHMWPE)织物/聚脲柔性复合材料；采用1.1 g柱状楔形破碎片，开展了弹道侵彻实验，并获取了弹道极限速度和比吸能；在此基础上，借助超景深显微镜及计算机断层扫描仪，观察侵彻后UHMWPE织物/聚脲柔性复合材料的表面及内部损伤形貌，分析抗破片侵彻机制。研究结果表明：UHMWPE织物/聚脲柔性复合材料抗破片侵彻性能具有明显的织物结构效应；相较于同厚度的叠层平纹织物增强聚脲柔性复合材料，角联锁织物增强聚脲柔性复合材料的弹道极限速度提升了4.9%;对于未被穿透的UHMWPE织物/聚脲柔性复合材料，其被侵彻过程主要包括聚脲对破片的包裹、剪切冲塞和纤维拉伸断裂破坏；叠层平纹织物的主要失效模式为剪切冲塞、分层失效，角联锁织物主要为纤维拉伸变形、拉伸断裂破坏。     

线迹缝合对芳纶平纹织物抗侵彻性能的影响

为了增强纱线间约束,提升平纹织物的抗侵彻性能,通过线迹缝合技术对织物内部纱线进行缝合.抽拔试验结果表明:线迹缝合有效增强了经、纬纱之间的摩擦力,织物的最大抽拔力随着缝合线迹数量的增多而增大.此外,线迹缝合增加了平纹织物的硬挺度.侵彻试验结果发现:高速侵彻降低了织物的能量吸收能力;试样的能量吸收能力随着相邻2根缝合线迹间距的减小而增大,其中每根纱线缝合试样的能量吸收能力最大;试样的贯穿比能量吸收能力随着相邻2根缝合线迹间距的减小呈现先增大后减小的趋势,每隔1根纱线缝合试样的贯穿比吸能最大.缝合结构与平纹组织的复合工艺为软体防弹服内胆防护层的优化设计提供了可行性方案.     

长径变化率对侵彻半无限厚靶板影响的数值模拟

应用LS-DYNA有限元程序,采用ALE方法在不改变侵彻体的材料、体积和质量情况下,对不同长径比的侵彻体侵彻半无限厚靶板进行了数值模拟,得到了侵彻过程中的主要物理图像和变化曲线。模拟结果表明:长径比较大的弹体虽然具有较强的侵彻能力,但随着侵彻体长径比的不断增大,它对侵彻效果的影响逐渐减弱。     

超高分子质量聚乙烯平纹织物在柔性防弹服中的应用

为提升柔性防弹服的防弹性能,将超高分子质量聚乙烯平纹织物用于单向铺层材料中,以增强材料整体的能量吸收性能。通过穿透性弹道实验发现:由超高分子质量聚乙烯纤维制成的机织物在冲击过程中对受到的剪切作用有较好的抵御效果;单向铺层材料对于横向拉伸作用,有较好的防护作用。基于这种结论,设计了复合型防弹材料。测试结果表明,机织物放置在靠近弹丸冲击的一侧,单向铺层材料放置在远离弹丸冲击的一侧,这种结构有利于防弹复合材料性能的提升。当复合型防弹材料中机织物与单向铺层材料质量比为1∶3时,其防弹性能最好。     

芳纶三维编织复合材料的抗冲击性能研究

用三维纺织结构复合材料的纤维倾斜模型在准细观结构层次上分解三维编织复合材料 ,建立与三维编织复合材料具有相同纤维体积含量的单向板细观模型。用动态显式算法有限元程序模拟倾斜单向板弹道侵彻破坏过程 ,并得到弹体贯穿靶体后的剩余速度和靶体变形形态。计算结果与弹道测试结果的比较证明在三维编织复合材料细观结构简化方案基础上计算三维编织复合材料弹道冲击性能的有效性。并简要讨论靶板破坏方式和破坏机理     

层后空间对防弹织物防护性能的影响

为探究层后空间对防弹织物弹道性能的影响，使用有限元方法建立了5个不同量级层后空间的Twaron^?弹道冲击模型，并对该模型进行了验证。分析对比了各模型下的黏土形变程度及黏土应变能吸收，并根据不同层织物的应变能情况，阐述了织物的能量吸收过程。最后，分析了有层后空间的防弹织物的破坏机理。有限元结果表明，层间距离最大的模型中，黏土形变最不明显且能量吸收最少，织物能量吸收最多。研究认为防弹织物若存在层后空间，防弹性能更好。且在0～8 mm范围内，层后空间越大，防弹性能越好，对人体损伤越小。究其原因就在于有层后空间的织物受到的反作用力更小，织物拉力更小，不容易发生破坏。     

双层复合非织造材料基吸声体吸声性能研究

以熔喷丙纶非织造材料和玻璃纤维水刺非织造材料为受声面和背衬层,通过热粘合方式制成双层复合非织造材料基吸声体。通过分析吸声体受声面和背衬层非织造材料的厚度、面密度、孔径、孔隙率等结构参数与复合吸声体的吸声系数之间的关系,探讨各层非织造材料结构参数对复合吸声体吸声性能的影响。实验结果表明,随着熔喷丙纶非织造材料和玻璃纤维水刺非织造材料厚度和面密度的增加,吸声体中高频段吸声系数显著提高;受声面和背衬层的孔径尺寸和孔隙率的变化对双层复合非织造材料基吸声体的吸声性能影响较为显著。     

双层及多层电磁屏蔽织物的屏蔽效能

为研究多层电磁屏蔽织物屏蔽效能情况,通过改变叠层角度、间距、叠层方式、层数,构建正交导电网格结构和单方向金属纱线平行结构的双层及多层电磁屏蔽织物,采用法兰同轴法测试其0.3~1.5 GHz内的屏蔽效能。结果表明,经纬向具有同样金属纱线间距时,织物屏蔽层厚度小于趋肤深度则双层织物的屏蔽效能明显高于单层织物,超过趋肤深度后增加不显著;3层及以上织物的屏蔽效能增加不明显;随层间距离增加,屏蔽效能呈增加趋势。仅纬向含金属纱线的双层织物,随双层织物中纬纱交叉角度的增加,逐渐形成金属纱线正交网格结构,屏蔽效能增大;双层织物中纬纱对齐叠放时,层间距离增加则屏蔽效能增大,纬纱垂直叠放时,层间距离增加则屏蔽效能降低。     

Hybrid panels from woven Kevlar® and Dyneema® fabrics against ballistic impact with wearing flexibility

.This paper reports on a study of hybrid ballistic panels consisting of plain-woven fabrics made from Kevlar® and Dyneema®, aiming to achieve protective and flexible ballistic panels. Experimental and numerical approaches were adopted for this research. Ballistic penetration tests indicated that the single-phase Kevlar® fabric panels was more energy absorbent than that of the Dyneema® fabric panels at low areal density. When the areal density reached around 1.4 kg/m2, the Kevlar® woven fabric panels started to outperform the Dyneema® counterpart in terms of energy absorption. Accordingly, hybrid panels from the two types of fabrics were engineered and such panels were associated to the higher specific energy absorption than the single-phase panels. It was also found that placing the Kevlar® fabric layer close to the impact face and the Dyneema® fabric layers towards the back face resulted in an improvement of around 16% in ballistic performance over the panels constructed in the reverse sequence. In this investigation, the optimum ratio of the two types of fabrics in hybrid panels was found to be 1:1.     

纱线弹道冲击的有限元模拟

纤维增强复合材料由于具有较低的面密度和较大的比吸收能,广泛应用在个体防护领域,而其中采用的高强纤维的断裂是最主要的吸能方式。以前的研究主要集中在弹道实验后对破坏模式的观察,为此采用有限元方法模拟了Twaron○R纤维束受到弹体侵彻的破坏过程,并与前人的实验结果进行比较,具有高度的相似性,进一步说明了纤维束的吸能机制,对软体结构防护系统的设计具有一定的指导意义。     

摩擦对平纹织物防弹性能影响的研究进展

在明确柔性材料防弹原理的基础上,从有限元建模分析和弹道测试2个方面,对弹丸与试样间摩擦、纱线与纱线间摩擦作用的运行机制进行了概述,分析了摩擦在弹丸能量吸收过程中起到的直接与间接作用,并且总结了提高摩擦性能的常用手法。研究发现：提升弹丸与材料之间的摩擦有利于材料应变能和动能的吸收,提升纱线间的摩擦有利于防止纱线滑移和扩大能量吸收区域的面积;纤维表面改性技术可使纤维间摩擦性能得到显著的提升,但很难满足产业化的需要;将纱罗组织与平纹组织相结合,可增大纬纱的摩擦包角,提升其纬向握持力。相比于表面改性过的纤维材料,纱罗/平纹复合组织能够在全自动织机上制备,可解决批量生产、人力成本过高等技术难题。     

Energy absorption of 3D orthogonal woven fabric under ballistic penetration of hemispherical‐cylindrical projectile

The non‐crimp features of warp and weft yarns impart the highest energy absorptions to 3D orthogonal woven fabric (3DOWF) than other kinds of 3D woven fabrics under ballistic impact. There are greater potential applications of the 3DOWF in ballistic protection. In this paper, an analytical model was proposed to calculate the energy absorption of the 3DOWF under ballistic penetration of a hemispherical‐cylindrical rigid projectile. The analytical model covers the calculations of the energies absorbed by the warp, weft, and Z‐yarns and the determinations of penetration time from the impact loading strain rate. The stress wave propagations in the warp, weft, and Z‐yarns were analyzed to formulate the fabric deformation and strain energy. The influence of strain rate on the residual velocities of the projectile was investigated. From the absorbed energy distribution calculated by the analytical model, the factors for improving ballistic performance of the 3DOWF are discussed.     

Evaluation of ballistic performance of hybrid Kevlar®/Cocos nucifera sheath reinforced epoxy composites

The aim of this research is replacement of petroleum resource-based costlier Kevlar^® 29 fabric (K) with a naturally woven novel Cocos nucifera sheath (CS) for ballistic applications. Cocos nucifera sheath is a bio waste, and it is termed as ‘Natural Textile’. Nine and twelve layered hybrid and nonhybrid laminates were fabricated with different layering sequence by hand lay-up method followed by hot pressing. Energy absorption and ballistic limit of the laminated composites were evaluated using a single stage gas gun ballistic setup with 8?mm hemispherical stainless steel projectile. The obtained results revealed that hybrid composites and CS/epoxy composite panels exhibited higher energy absorption (30%) and ballistic limit (13%) compared to Kevlar^® fabric/epoxy composites. It is due to CS’s chemical composition, architecture, and unique shock wave dissipation mechanism. Hence, this new eco-friendly material will efficiently replace Kevlar^® fabric in the ballistic composites.     

Ballistic performance of angle-interlock woven fabrics

The purpose of this paper is to investigate the ballistic performance of angle-interlock woven fabrics. Different fabric structures firstly have been compared to benchmark the ballistic performance of angle-interlock woven fabrics using the energy loss test. It has been shown that compared with other woven structures, angle-interlock woven fabric demonstrates low ballistic resistance as absorbing less impact energy. This is because angle-interlock woven fabric owns less interlacements than its counterparts. The interlacement plays an important role to help to transfer energy to the adjacent yarns: the more interlacements, the larger area the stress wave could propagate, and more projectile impact energy could be absorbed. After this systemic analysis of overall ballistic performance, more detailed parametric study of angle-interlock woven fabric is carried out. A group of 16 different structures have been tested and compared using the in-house firing range. The studies have revealed that the 3D angle-interlock woven fabric not only displays normal features of energy absorption mechanism, like yarn slippage, fibre fracture and cone formation, which 2D fabric usually demonstrates, but also shows the new property: the weaker gripping power on the constituent yarns. Besides, it also shows that the structural parameters of angle-interlock fabrics do not have a clear influence on the ballistic performance, due to the complicated factors which also have been theoretically explained from the four aspects: (a) the clamping state; (b) yarns hit by the projectile; (c) the impact angle of the projectile; (d) the impact velocity.     

Finite element simulation of three‐dimensional angle‐interlock woven fabric undergoing ballistic impact

This paper presents finite element simulations of three‐dimensional (3D) angle‐interlock woven fabric (3DAWF) undergoing ballistic impact. A micro‐structure model of the 3DAWF was established at the fiber tow level. Incorporated with commercial finite element code, ABAQUS/Explicit, the ballistic impact damage of the 3DAWF was simulated and compared with that in the experiment. Residual velocities of the conically cylindrical steel projectile (Type 56 in Chinese Military Standard) with different strike velocities were calculated and verified with those in the experiment. There are good agreements of the impact damage of the 3DAWF and the residual velocities of the projectile between finite element results and experimental results. The acceleration fluctuation record of the projectile and the stress wave propagation in the 3DAWF obtained from the simulation reveal the impact damage mechanisms of the 3DAWF. The strain rate effect of the fiber tows on the ballistic performance are also discussed. Such a micro‐structure model could be extended to the design of the impact behavior of the 3DAWF composites.     

芳纶织物及其包容环的弹道冲击与数值模拟

为研究芳纶织物及其包容环的弹道冲击机制,通过准静态及动态拉伸实验获取材料力学性能,采用弹道冲击实验获得织物及包容环的冲击性能,同时建立多层壳模型并基于实验结果进行验证。结果表明:应变率对织物力学性能有较为显著的影响,在织物弹道冲击中织物吸能量与失效模式相关,呈现明显的边界效应;在包容环弹道冲击中,能量的耗散主要是通过纱线应变能、纱线断裂以及纱线间相互作用;相同入射速度下,织物层数越少,吸能量越少,织物层数增加时吸能量增大,但吸能增加量减小;多层壳模型能够较好地复现弹道冲击过程,仿真失效形貌、弹体剩余速度和吸能比率均与实验结果接近。     

Finite element analyses of stress distributions of three-dimensional angle-interlock woven composite subjected to three-point bending cyclic loading

This paper presents the finite element simulation of stress distribution features of 3D layer-to-layer angle-interlock woven composite undergoing three-point bending cyclic loading. With the finite element analysis model, a microstructure shell element model of the woven composite at yarn level was established to calculate the fatigue behaviors and stress distribution during cyclic loading. The stress distributions in the warp, weft yarns, and the resin regions have been calculated to show the stress difference in the woven composite. It has been observed that the warp yarns share the most part of the stress or loading, i.e. the strength warp yarn is more important than that of the weft yarn for the fatigue design. In addition, the stress distributions at the locations where the weft yarns crossover the warp yarns have been investigated. The stress degradations of the top and bottom surface of the woven composite panels were also compared with those in experimental and good agreement was found. With the stress distribution in the woven composite, the method of improving the fatigue damage tolerance was expected to be developed.     

圆柱壳双开孔-接管结构的应力分布研究

针对化工过程装备中经常遇到的圆柱壳双开孔-接管结构,采用有限元分析方法获得轴向和环向双开孔-接管结构的应力集中系数分布图。分析结果表明,开孔率和开孔间距大小是影响筒体开孔接管区应力分布的主要因素。开孔率决定了开孔影响区的范围以及结构的最大应力集中系数,而开孔间距的变化直接影响到筒体孔桥部位上最大应力水平。研究结果为此类结构安全评定及优化设计提供有效手段。