碳纤维结构吸波材料及其吸波碳纤维的制备

碳纤维结构吸波材料是一类多功能复合材料,具有承载和减小雷达反射截面的双重功能,是一种非常有发展前途的吸波材料。碳纤维结构吸波材料以其优异的力学性能和隐身特性已大量应用于隐身技术。本文讨论了碳纤维结构吸波的应用,碳纤维结构吸波材料的类型及其结构型式设计,探讨了吸波波对碳纤维进行掺杂改性,制备出吸波性能优良的碳纤维、改变碳纤维的截面形状和大小,对碳纤维进行表面改性以及对碳纤维进行掺杂改性,制备出吸波性     

结构型碳纤维吸波复合材料的研究及应用

结构型碳纤维吸波复合材料结合了复合材料轻质高强的结构优势和吸波特性,是雷达隐身材料的重要发展方向。本文主要从异型截面碳纤维、手性碳纤维和碳纳米管等新型吸波碳纤维增强体以及夹芯结构、点阵结构形式等方面总结了结构型碳纤维吸波复合材料国内外的最新研究和应用进展,并指出了未来发展方向。     

炭纤维吸波复合材料结构设计的研究进展

总结了炭纤维吸波性能的电磁改性方法,重点介绍了结构设计对炭纤维吸波复合材料吸波性能的影响,包括短切炭纤维、炭纤维排布结构、炭纤维电路模拟结构以及含炭纤维的混杂纤维排布对炭纤维复合材料吸波性能的影响.提出了炭纤维吸波复合材料今后的研究方向.     

陶瓷纤维吸波材料的吸波机理及其结构设计

陶瓷纤维复合材料在结构及隐身技术中得到了广泛的应用。通过分析陶瓷纤维材料的吸波机理以及结构特性对纤维材料的电磁参数和吸波性能的影响，提出了综合不同方法来对吸波纤维进行结构设计的构思。     

单/双层水泥基平板的微波吸收性能

依据阻抗匹配原理与电磁波传播规律,提出表层透波、内层吸波的双层法设计,该设计具有电磁波吸收性能的层状水泥基平板结构.研究了硅灰和橡胶粉对表面层阻抗匹配的影响;同时还对碳纤维、钢纤维、碳纤维与铁氧体粉复合以及钢纤维与碳纤维复合作为内层吸收剂时,水泥基平板材料在8～18GHz频段内的吸波性能进行了研究.结果表明:硅灰和橡胶颗粒可以明显地改善水泥平板与自由空间的阻抗匹配:与单层相比,在相同碳纤维掺量时,双层吸波砂浆反射率下降-3dB左右;30%质量分数铁氧体与碳纤维复合作为吸波材料的损耗层的吸收剂,反射率在-10dB以下(12.5～18.0GHz),且随着入射频率的增加反射率下降.     

结构型吸波复合材料的研究进展

结构型吸波复合材料具有吸波性能好、质量轻、可承载等优点,已成为当代吸波材料的主要发展方向,对隐身材料的设计和制造有着重要意义。本文从纤维增强体的截面形状和制备工艺、纤维的铺排结构和夹层复合结构、吸波剂改性等影响吸波复合材料吸波性能的主要因素出发,系统地总结了结构型吸波复合材料的最新研究热点和成果,并指出吸波复合材料的未来发展方向。     

吸波纤维研究进展

介绍了目前复合吸波材料中所用的吸波纤维，包括碳纤维、碳化硅纤维、多晶铁纤维等及其改性纤维的吸波机理和性能。简述了吸波纤维在复合材料中的排布方式、长度和含量对材料吸波性能的影响。综述了吸波纤维的研究现状和进展。     

夹杂长碳纤维束电路模拟结构复合材料吸波性能

利用玻璃纤维夹杂长碳纤维束的方式制作了两种碳纤维含量的电路屏,真空成型的方式制作了测试样板。研究了电路屏中碳纤维含量、电路屏铺层结构以及铺层厚度对复合材料电磁吸收性能的影响。在本试验条件下,随着碳纤维含量的增加复合材料样板的吸波效果有明显的增加;在入射波方向,碳纤维含量先递增再递减的铺层方式,吸收雷达波效果优异;采用此种梯度铺层方式,且每种碳纤维含量的电路屏铺3层的梯度铺层方式制得的复合材料样板在25.6～40 GHz波段吸收效果最好。     

乙炔炭黑/铁氧体复合材料的阻抗匹配设计及其吸波性能研究

从阻抗匹配设计的角度,用铁氧体、乙炔炭黑(CB)等填充丁腈橡胶(NBR)制备了不同结构的吸波材料,用自由空间法测试了复合材料的吸波性能。结果表明:铁氧体的输入阻抗比CB的小,与自由空间的匹配较好;二层和四层结构的吸波材料明显好于单层结构的吸波材料的性能;二层和四层结构的吸波材料明显好于单层结构的吸波材料的性能,四层结构NBR/CB(100/25)复合材料的最大吸收衰减达到11.4 d B。     

羰基铁粉-碳纤维水泥基复合材料的吸波性能

采用海军研究实验室反射率测试系统,研究了单掺碳纤维和复掺羰基铁粉碳纤维水泥基复合材料在2～18GHz频率段的吸波性能.利用扫描电镜和X射线衍射仪分析了复合材料微观结构和组成成分的变化.结果表明:单掺碳纤维时,在2～8GHz低频率段,反射率随碳纤维掺量增加逐渐增强;在8～18 GHz高频率段,随碳纤维掺量增加.复合材料吸...     

频率选择表面在吸波材料中的应用进展

频率选择表面(FSS)是一种二维周期性结构,可以有效地控制电磁波的反射与传输。介绍了FSS在吸波材料中的应用进展情况。     

吸波边界对Lamb波在复合材料中传播的影响研究

运用Lamb波对复杂结构进行结构健康监测时,经常需要对Lamb波传播过程进行有限元仿真,但由于建模大小、复合材料各向异性等原因,会产生较多的边界反射波,从而掩盖损伤波形,因此建立吸收边界抑制反射波的影响就显得尤为重要。使用加入弹簧阻尼器Combin14单元的吸波边界,研究了吸波边界长度、频率、Combin14单元方向等对该吸收边界吸波效果的影响,并通过与传统的阻尼递增吸收边界进行对比,发现频率和吸波边界长度对弹簧阻尼器吸波边界吸波效果均无过大影响,但其吸波边界长度必须大于λ(波长)才会达到最优效果;当Combin14单元设置在沿传播方向时的吸波效果最好;相较于阻尼递增吸波边界,弹簧阻尼器吸波边界的仿真耗时明显减少且在低频段的吸波效果更好。     

Multiscale designed SiCf/Si3N4 composite for low and high frequency cooperative electromagnetic absorption

With the aim to design a particular material for low and high frequency cooperative electromagnetic absorption at high temperature, a multiscale design is proposed by combining the microstructure and meta‐structure in one material. The SiC_f/Si₃N₄ composite is prepared via the chemical vapor infiltration technique with SiC_f as the EM wave absorbing phase and Si₃N₄ as the wave‐transparent ceramic matrix. The crossing grooved meta‐structure is designed and fabricated to further improve its absorbing properties and to guarantee its absorbing capacity stability at high temperature. A minimum reflection loss of ?15.3 dB and ?14.8 dB can be reached at 8 and 18 GHz with a total thickness of 5 mm. The temperature‐dependent reflection loss of the designed meta‐structure keeps relative reliable high temperature absorbing performances from room temperature to 500°C. This effective enhanced EM wave absorbing property is believed to be a consequence of multiscale effect induced by combining the traditional EM absorbing materials with metamaterial structure.     

聚脲弹性体复合夹层结构的防爆性能

应用LS–DYNA有限元软件,对聚脲弹性体复合夹层结构在0.5 kg炸药(TNT)爆炸载荷作用下的动态响应过程进行数值模拟。研究了复合夹层结构厚度和质量固定条件下聚脲弹性体夹层厚度对复合夹层结构抗爆性能的影响。分析了不同聚脲弹性体夹层厚度对复合夹层结构变形的影响,并分析了聚脲弹性体夹层的吸波和吸能特性。结果表明,在爆炸载荷作用下,当复合夹层结构总厚度固定时,随着聚脲弹性体夹层厚度的减小,复合夹层结构的抗爆性能先增大后减小,当钢板与聚脲弹性体夹层厚度比为1.4∶1.2∶1.4时,变形的整体性最好,其抗爆的潜力最大,其冲击波衰减率最大为85.6%,能量吸收效果也最好,其综合抗爆能力较好;在质量固定条件下,随着聚脲弹性体夹层厚度的增加,其抗爆能力先增大后减小,当钢板与聚脲弹性体夹层厚度比为0.903∶3.5∶0.903时,其变形和能量吸收效果最好,冲击波衰减率最大为81.87%,其综合抗爆能力较好。     

石墨烯/Fe3O4/FeSiAl复合材料的制备及吸波性能

以FeSiAl片状磁粉、膨胀石墨为主要原料,采用水热法制备石墨烯/Fe_3O_4/FeSiAl复合材料。通过XRD、SEM、Raman、FTIR和矢量网络分析仪(VNA)对石墨烯/Fe_3O_4/FeSiAl复合材料的晶相、微观形貌和吸波性能进行了表征和分析。结果表明:通过水热还原法,将氧化石墨烯还原成石墨烯,并且生成的石墨烯及Fe_3O_4颗粒均匀包覆在FeSiAl片状磁粉上,这种片状和颗粒状不同结构的复合,制备出了兼具磁损耗和介电损耗的吸波材料。在0.2~2.66 GHz频段内,当氧化石墨烯和FeSiAl质量比为1∶9,相应匹配厚度为2 mm时,石墨烯/Fe_3O_4/FeSiAl复合材料在2.56 GHz处最小反射率可达到–17 dB,其有效吸收频带范围(反射率小于–10 dB)为2.27~2.66 GHz。随着氧化石墨烯与FeSiAl质量比的增加,石墨烯/Fe_3O_4/FeSiAl复合材料的有效吸收频带向高频移动,有助于该吸波材料在高频段的应用。     

Dual gradient direct ink writing of functional geopolymer-based carbonyl-iron/graphene composites for adjustable broadband microwave absorption

As a novel type of moulding technology, additive manufacturing (AM) can realise the rapid manufacturing of complex structures. This research applied dual gradient direct ink writing (DGDIW) with in-situ dispersion to fabricate multi-materials in an extensive gradient range. Functionally graded materials (FGM) have emerged as intelligent composites with peculiar advantages in wave absorption applications. An FGM geopolymer containing carbonyl-iron and graphene (CIG) powders with graded structure was successfully fabricated to enhance the wave-absorbing property via DGDIW three-dimensional (3D) printing. Compared with the non-structured homogeneous geopolymer composites, FGM composites performed more consecutive and effective absorbing from 2 to 18 GHz, resulting in a significantly increased electromagnetic (EM) wave absorption property. Combining with the gradient content of CIG fillers, the impedance matching and electromagnetic attenuation of 3D printed gradient lattice structure geopolymer composites has been significantly improved, the minimum reflection loss can reach ?46.47 dB at 17.58 GHz with a broadband absorption of 14.62 GHz (3.38–18.00 GHz). The results provided a promising strategy for fabricating functional graded ceramic composites with great potential as an absorption device in wave absorption applications, especially in protective structures, radiation-proof equipment/architecture, and defence constructions.     

碳纳米管在聚合物基吸波复合材料中的应用

碳纳米管作为一种新型电磁吸波剂,因其独特的物理和化学性能引起了人们极大的关注。本文简述了碳纳米管的吸波机理及吸波性能的表征,重点介绍了碳纳米管在聚合物吸波复合材料中的应用,如碳纳米管/树脂基复合材料、碳纳米管/导电高聚物复合材料、碳纳米管/橡胶基复合材料,最后展望了吸波材料的发展方向。     

含有短切导电纤维聚氨酯泡沫塑料的吸波性能研究

通过对一种含导电短纤维的聚氨酯(PUR)泡沫塑料吸波性能的研究,探讨了纤维吸收剂的电导率、含量和泡沫塑料试样厚度对PUR泡沫塑料吸波性能的影响。结果表明,在一定范围内,纤维电导率增大可使PUR泡沫塑料对电磁波的损耗增加;纤维含量增大可增加其谐振子数目,有利于衰减电磁波;试样厚度增加可使PUR泡沫塑料吸波性能增强,在Ka波段尤为明显。     

Broadband electromagnetic wave absorption of Ni0.5Zn0.5Nd0.04Fe1.96O4 ferrites modified by nano-silver particles

Ferrite materials have the potential to become excellent absorbing materials due to their high magnetic loss and good impedance matching. However, the disadvantages of high density and lack of dielectric loss capability limit its application. Herein, we used the citric acid sol-gel method and the self-propagating combustion method to prepare neodymium-doped nickel-zinc ferrite (NZNF), then the target effect of Sn²⁺ and an improved electroless silver plating process was used to plate a layer composed of silver nanoparticles (Ag NPs) with strong dielectric loss on the NZNF, and a magnetic/dielectric composite material (NZNF@Ag) with a heterogeneous structure was prepared. The number and particle size of Ag NPs on the surface of NZNF can be precisely controlled, thereby greatly enhancing the dielectric loss capability with little impact on the magnetic loss. The huge difference in conductivity between conductors and semiconductors promotes the occurrence of polarization at the heterogeneous interface and significantly enhances the electromagnetic wave absorption ability of the composite material. In the 2–18 GHz frequency band, the best sample can obtain an effective bandwidth of 6.82 GHz when the matching thickness is 2.1 mm. Combining conductors with semiconductor materials to obtain significantly enhanced interfacial polarization provides a new idea for improving the performance of wave absorbing materials.     

New insights into the damage assessment and energy dissipation weight mechanisms of ceramic/fiber laminated composites under ballistic impact

Ceramics/composite laminated armor structures have become the mainstream in the design of bulletproof materials. To obtain systematic improvements in composite targets, it is essential to design the structure of each ceramic/fiber to ensure synergistic energy matching between them. However, the challenges of heavy workload and high-costs limit the experimental testing of these composites. In this report, B₄C ceramics/ultra-high molecular weight polyethylene (UHMWPE) composite targets are studied and the impact of ceramic splicing size, impact position and size on the anti-elastic performance is predicted. Finite element analysis is used to comprehensively analyze critical obstacles of the failure damage, energy dissipation weight and ballistic mechanism of each material. Prediction results indicate that ceramics damage, fiber damage, and fiber delamination account for about 65%, 21%, and 14% of the total energy consumption, respectively. Square splicing and large size ceramics/fiber composites are found to have the best anti-elastic properties when the center position is impacted. This is ascribed to the transversal rapid stress wave propagation on the ceramic surface and the beneficial energy dissipation of the composite-backing arising from the longitudinal stress wave transfer of homogeneous panels. The results provide insights for identifying viable design methods for each structure, optimizing the matching of panels and backplanes, which reduces the number of experimental tests need to validate a given structure.