碳纤维增强水泥基复合材料的吸波性能研究

利用弓形反射法(NRL)测试了碳纤维掺量分别为0.2%、0.4%、0.6%、0.8%和1.0%(质量分数)时碳纤维增强水泥基复合材料(CFRC)在低频段4～8GHz和高频段8～18GHz时的反射率,讨论了纤维掺量、频率、反射率之间的关系.结果发现,在纤维掺量相同条件下:低频段时,反射率＜-10dB,CFRC表现出吸波性;高频段且纤维掺量超过0.6%(质量分数)时,反射率＞-10dB,CFRC对电磁波表现出反射性.随着纤维掺量的增加,低频段时反射率先降低、后又有所回升,吸波性由弱变强、又变弱,纤维掺量为0.6%(质量分数)时出现最小反射率-15.0dB;高频段时反射率总体上呈上升趋势,材料对电磁波的反射性越来越强,纤维掺量为0.4%(质量分数)时出现最小反射率-19.4dB.     

含涤废弃织物增强水泥基透水砖的制备及表征

采用涤棉混纺(P/C)和涤纶(PE)废弃织物增强水泥基透水混凝土砖,分析织物含量和织物尺寸等因素对复合透水砖(CPB)抗压性能、透水性和保水性的影响。结果表明:随着织物掺加体积分数的增加,CPB的抗压强度、压缩韧性指数和所消耗能量先增大后减小,透水系数和保水系数增加;随着织物尺寸增大,CPB的抗压强度、透水系数和保水系数逐渐减小,压缩韧性指数增加,耗能变化幅度不大;在织物和纤维掺加量较小且掺加质量相同的条件下,与废弃织物CPB相比,再生纤维CPB的抗压强度较小,而压缩韧性指数、耗能和透水系数较大;当织物掺加体积分数≤2%时,涤棉复合透水砖(PC-CPB)的抗压强度优于涤纶复合透水砖(P-CPB),透水系数、保水系数和P-CPB接近,当织物掺加体积分数>2%时则相反,而PC-CPB的压缩韧性指数和耗能始终优于P-CPB;织物掺加体积分数为2%的3 mm×3 mm P/C织物所制备的CPB抗压强度为28.20 MPa,耗能为1097.55 N·m,透水系数为0.267 mm/s,保水系数为43.40 g/cm2,与普通透水砖相比,分别提高了21.8%、55.8%、115.3%和33.3%。      

不锈钢纤维混纺织物抗静电功能与风格

基于对表观直径12μm／45mm不锈钢纤维与1．33dtex／40mm阻燃粘胶纤维基本性能的研究，设计了不锈钢纤维含量1％～40％的10种混纺纱线及织物，实验分析了不锈钢纤维混纺织物力学、电学、热学、光学等主要特性，得出织物中不锈钢纤维含量1％可得到抗静电性能极好的静电耗散纺织品；含量在10％～40％可制成静电导体、导电织物静电屏蔽材料；混纺织物强伸性、绝热、透湿率、对可见光的反射率等主要风格随不锈钢纤维含量增加均呈下降趋势等主要结论。     

层状碳纳米管/石英复合材料的制备及其微波衰减性能

采用溶胶-凝胶法合成了3种不同体积分数的碳纳米管/石英复合粉体,将其中的2种复合粉体先后装入同一石墨模腔中,经热压烧结获得致密的层状碳纳米管/石英复合材料.测试了层状复合材料在8.2～12.4GHz波段的微波衰减性能,研究发现,层状碳纳米管/石英复合材料具有优良的微波衰减性能,并且微波从不同的材料面入射对微波产生的反射差别很大.对于10%(体积分数)碳纳米管/石英-纯石英层状复合材料,微波从10%(体积分数)碳纳米管/石英面入射造成的微波反射量是从纯石英面入射造成的微波反射量的5倍以上.采用层状设计制备了一种对微波反射少、吸收量大的碳纳米管/石英复合材料.     

纳米粘土/环氧树脂复合材料的制备及力学性能研究

借助超声分散,采用固化处理制备了不同纳米粘土掺量(0,1%,3%,5%和7%(质量分数))的纳米粘土/环氧树脂复合材料,研究了纳米粘土掺量对复合材料性能的影响。通过X射线衍射(XRD)、力学性能测试、扫描电镜(SEM)等对复合材料进行了表征。结果表明,不同掺杂比例的纳米粘土和环氧树脂都均匀结合,纳米粘土掺量为7%(质量分数)的复合材料衍射峰强度最高,其结晶性能最佳;随着纳米粘土掺量的增加,复合材料的拉伸模量、极限抗压强度和断裂韧性KIC值整体均高于纯环氧树脂,而复合材料的破坏应变低于纯环氧树脂;当纳米粘土掺量为1%(质量分数)时,复合材料的极限抗拉强度略有提高,但随着纳米粘土掺量的继续增加,复合材料的极限抗拉强度逐渐降低;当纳米粘土掺量为5%(质量分数)时,复合材料的拉伸模量达到3 513 MPa,相比纯环氧树脂的3 300 MPa,增加了6.5%;当纳米粘土掺量为7%(质量分数)时,复合材料的断裂韧性KIC值达到1.97 MPa·m~(1/2),相比纯环氧树脂的1.60 MPa·m~(1/2),增加了23.1%;纯环氧树脂的断裂表面光滑无褶皱,断裂时裂纹没有产生无偏离的扩展,而复合材料的断裂表面随纳米粘土掺量的增加均趋于粗糙,裂纹在扩展过程中发生了偏移。     

玻璃纤维-磷酸盐保温发泡材料的制备及性能研究

通过预混法制备了不同玻璃纤维(0%,3%,6%,9%质量分数)掺量的玻璃纤维-磷酸盐保温发泡材料,对该发泡材料的应力/应变、抗压强度、粉化率、导热系数和热稳定性等进行了分析。结果表明,随着玻璃纤维掺量的增加,玻璃纤维-磷酸盐保温发泡材料的应力/应变、抗压强度、质量损失率和热失重逐渐增大,粉化率逐渐降低,而导热系数无明显变化。当玻璃纤维的掺量为9%(质量分数)时,发泡材料的应变达到0.1,应力达到594 MPa,对应的抗压强度达到最大为497 MPa,与不掺杂玻璃纤维的样品相比提高了152.3%。当玻璃纤维的掺量从3%(质量分数)增加到6%(质量分数)时,发泡材料的粉化率降低了33.0%;当玻璃纤维的掺量从6%(质量分数)增加到9%(质量分数)时,发泡材料的粉化率降低了8.5%。4种玻璃纤维-磷酸盐保温发泡材料经过不燃性测试后,形貌和体积的变化不大,只是表面出现炭化现象,发泡材料的导热系数与玻璃纤维的掺量并无明显关系。     

短切纤维及预应力对玄武岩织物增强水泥基复合材料拉伸力学性能的影响

通过静态拉伸试验研究不同体积掺量的短切碳纤维、钢纤维、耐碱玻璃纤维及预应力对5层玄武岩织物增强水泥基复合材料(BTRC)拉伸性能的影响。试验结果表明:短切碳纤维、玻璃纤维可以提高基体和BTRC的开裂强度,且开裂强度随着碳纤维掺量的增加而增加;预应力使基体产生预压力,明显提高其开裂强度。短切纤维及预应力都显著提高BTRC的峰值荷载和韧性,但峰值应变基本不变;峰值荷载和韧性随着钢纤维掺量的增加而增加,体积分数为1.5vol%掺量时达到最大值;随着碳纤维掺量增加,峰值荷载和韧性先增加后减小,体积分数为1.0vol%掺量时最大。施加预应力且掺入短切碳纤维或钢纤维时,短切纤维增强的基体可以更好地承受张拉力释放后纤维束径向变形引起的环向应力,进一步提高了织物与基体界面的挤压作用力及摩擦力,从而增强效果最明显,峰值荷载分别增加50.4%和58.9%,韧性分别增加84.7%和79.5%。BTRC材料掺入短切玻璃纤维、钢纤维及施加预应力均可以增加其受力后的裂缝条数,减小裂缝间距和裂缝宽度。     

消防避火服外层织物辐射热防护效能研究

通过对高硅氧玻璃纤维织物(A1)、高硅氧玻璃纤维织物(B1)、连续玄武岩纤维织物(XW)三类消防避火服外层织物材料进行比热容、X射线衍射图谱与热射线反射率等织物辐射热防护性能相关指标的测定,比较了三类消防避火服外层织物材料的防护性能,并从微观纱线分子架构等角度对造成三类材料辐射热防护性能差异的原因逐一进行了解释与分析。根据分析与计算结果,认为纤维内部微观结构与织物辐射热防护能力有着较为紧密的联系,纤维结晶度对织物热射线反射能力的影响显著。     

淀粉膨胀石墨相变复合材料的制备及性能研究

介绍了一种利用的乳化机理制备淀粉膨胀石墨相变复合材料的方法。以石蜡、膨胀石墨(expanded graphite, EG)和淀粉为原材料,制备淀粉膨胀石墨相变复合材料,并对其性能进行研究。研究表明,红外光谱显示石蜡、EG和淀粉之间是物理结合,没有新物质生成。复合相变材料的储热能力随着相变材料的减少而降低。当EG掺量8.4%(质量分数)时,相变热逐渐减少,当EG掺量8.4%(质量分数)时,相变热急剧减少。相变复合材料热导率随着EG掺量的增加而增大。当EG掺量8.4%(质量分数)时,热导率逐渐增加。当EG掺量8.4%(质量分数)时,热导率增幅较小。EG的掺量为8.4%和11.0%(质量分数)时,扫描电镜显示淀粉膨胀石墨相变复合材料由许多微小的胶囊颗粒组成。相变材料被稳定的封装在微胶囊中,以防止在相变过程中发生泄露。综合考虑其储热性、导热性和稳定性,研究得到EG在复合相变材料中的最佳掺量为8.4%(质量分数)。     

BFRC中玄武岩纤维的分散性与胶砂流动性

通过机械力及材料间的摩擦并不能使玄武岩纤维有效分散于水泥砂浆基体中。选用羧甲基纤维素(CMC)作为分散剂,采用超声波振荡,当胶砂流动度大于170mm时,实现了玄武岩纤维在水泥基体中的均匀分散。CMC分散剂有助于纤维分散,其水溶液质量分数宜保持在1.56%～1.77%间,温度宜控制在40～44℃。随着纤维含量的增加,玄武岩纤维增强水泥基复合材料(BFRC)的胶砂流动性逐渐降低,粉煤灰掺量达20%以上时,BFRC的胶砂流动性显著提高,掺量不超过25%时,BFRC的28d抗折、抗压强度均有所提高。     

钢纤维水泥基材料吸波性能实验与隐身效能分析

采用远场雷达散射截面法测试的功率反射率为表征吸波性能的指标,研究了素砂浆的吸波性能以及钢纤维长度、钢纤维掺量、复掺铁氧体、表面处理、温度和湿度等因素对钢纤维砂浆吸波性能的影响;同时根据所推导的隐身效能评价公式计算了钢纤维砂浆的隐身能力.研究表明:掺入钢纤维可以提高砂浆的低、高频吸波性能;合适的纤维长度和体积掺量是提高砂浆吸波性能的决定性因素;温、湿度升高,钢纤维砂浆的吸波性能下降;复掺的铁氧体分布在试件表层时,钢纤维砂浆的吸波性能下降,而分布在整个试件内时,可提高低频段的吸波性能;表面开浅槽可以在较宽的频段内提高吸波性能,表面开深槽可使低频吸波效果明显提高;吸波效果较好的钢纤维砂浆在2.6～4GHz的频段内,其雷达最大探测距离可降低到素砂浆的84%～89%.     

纳米SiC纤维改性短切碳纤维增强Si_3N_4陶瓷介电响应及吸波性能

以甲基三氯硅烷为原料,采用催化化学气相沉积(CCVD)工艺在短切碳纤维(C_(fd))表面制备了纳米SiC纤维(nano SiC_f)改性层,并采用凝胶注模-无压烧结工艺制备了nano SiC_f-C_(fd)/Si_3N_4和C_(fd)/Si_3N_4复合材料。使用矢量网络分析仪研究了nano SiC_f-C_(fd)和C_(fd)对Si_3N_4陶瓷在X波段(8.2~12.4GHz)的介电响应和吸波性能的影响。结果表明:nano SiC_f-C_(fd)/Si_3N_4和C_(fd)/Si_3N_4复合材料的复介电常数和介电损耗角正切值(tanδ)均随纤维添加量增加而增大;相同纤维含量时,nano SiC_f-C_(fd)/Si_3N_4复合材料的介电常数实部比C_(fd)/Si_3N_4复合材料有所降低,但损耗角正切升高。反射损耗结果表明:nano SiC_f-C_(fd)/Si_3N_4复合材料拥有更优的电磁波吸收效果。nano SiC_f-C_(fd)含量为2wt%、d=2.5mm时,出现最大吸收峰-14.95dB,反射损耗优于-5dB,波段频宽达3.5GHz。nano SiC_f界面改性能有效提高C_(fd)/Si_3N_4复合材料的吸波性能。     

Electrical and impact properties of the hybrid knitted inlaid fabric reinforced polypropylene composites

A range of conductive knitted fabric reinforced polypropylene composites have been developed and their electromagnetic shielding effectiveness (EMSE), electrostatic discharge (ESD) and impact properties have been investigated. Carbon and aramid fibers are used as the reinforcement phase in the composites, while copper and stainless steel wires are incorporated as conductive fillers to provide the ESD and EMSE properties of the composite materials. The hollow spindle spinning system has been used to make SS/PP, Cu/PP, SS/C/PP, Cu/C/PP and Cu/K/PP uncommingled yarns. The double plain knitted fabric and its inlaid fabrics were fabricated from the yarns using a 5G traverse knitted machine. Changing the yarn composition, fabric knit structure, and stitch density varies the amount of copper and stainless steel conductive fillers in the composites. 4 layer cross-ply laminates were laid-up by hand, then formed into 3-mm thick conductive thermoplastic composites using a compression molding. It was observed that the EMSE and ESD of the composites increase with increasing the incident frequency, especially at higher frequency range. The effects of inlaid ends, materials and yarn constitutions on the EMSE of the conductive thermoplastic composites were investigated. The results indicate that the composites can be used for the purpose of electromagnetic shielding and ESD attenuation, as well as for some microwave applications.     

Phase transformation of 316L stainless steel from wire to fiber

In this work, quantitative crystalline phase analysis of 316L stainless steel from wire to fiber using a multi-pass cold drawing process was studied using the Rietveld whole XRD profile fitting technique. The different diameters of the fibers: 179, 112, 75, 50, 34, 20, and 8 μm, were produced from an as-received wire with a diameter of 190 μm. The crystalline phases were identified using MDI Jade 5.0 software. The volume fractions of crystalline phases were estimated using a Materials Analysis Using Diffraction software. XRD analysis revealed that the crystal structure of as-received wire is essentially a γ-austenite crystalline phase. The phase transformation occurred during the 316L stainless steel from wire to fiber. Three crystalline phases such as γ-austenite, α′-martensite, and sigma phase of the fine fiber were observed. A cold drawing accelerates the sigma phase precipitates, particularly during the heat treatment of the fiber.     

Surface damage of unidirectional carbon fiber reinforced epoxy composites under reciprocating sliding in ambient air

For many technical applications friction and wear are critical issues. Reinforced polymer-matrix composites are widely used under vibrating contact condition in various automotive and aerospace applications as well as in structural engineering. In this paper, the friction and wear of bulk epoxy and unidirectional carbon fiber reinforced epoxy composite have been investigated under reciprocating sliding against either alumina or stainless steel balls in ambient air. The effect of sliding direction with respect to the long and unidirectional carbon fibers has been studied. We demonstrate that the carbon fiber reinforcement greatly improves the tribological properties of the thermoset epoxy: it reduces the coefficient of friction and the debris formation. It was found that on sliding in the anti-parallel direction a more significant degradation takes place than in the parallel direction. The coefficient of friction measured on bulk epoxy sliding against either stainless steel or alumina is around 0.65, whereas the coefficient of friction measured on epoxy reinforced with carbon fibers is significantly lower, namely down to 0.11. It was found that sliding with a stainless steel ball in a direction parallel to the fiber orientation results in a lower coefficient of friction than sliding in anti-parallel direction. The reduced coefficient of friction is largely influenced by the carbon fiber reinforcement due to the auto-protecting film formed as a paste in the contact area and along the wear track edges. The relationship between friction and degradation of the composite material including surface wear and debris formation are discussed based on an in-depth analysis of the worn surfaces by optical and scanning electron microscopy, micro-Raman spectroscopy, and white light interferometry.     

Processing of metallic fiber hybrid spun yarns for better electrical conductivity

This research was aimed at processing of metallic fiber hybrid spun yarns consisting of polyester/stainless steel and viscose/stainless steel staple fibers to achieve better electrical conductivity. Conventional ring spinning machine and ring twister machine were used to produce the single and plied yarns respectively. The linear electrical resistance of yarns was analyzed with reference to the three levels of twist multiplier (TM) for same yarn count, three levels of yarn fineness (Ne) at the same TM level, and number of plies for the same final yarn count. These results showed that by increasing twist, the electrical conductivity of yarn was increased. However, yarn fineness was in inverse relation with the electrical conductivity of yarns. The effect of yarn plying and twisting to produce the Ne 10s yarn was also found critical in governing the electrical properties. The electrical conductivity of viscose and stainless steel hybrid yarn was found more sensitive to increase with an increase in relative humidity contrary to that of polyester and stainless steel hybrid yarns. The findings of the study are significant to produce the hybrid spun conductive yarns for their potential applications in a variety of tailor-made functional, protective and smart textiles.     

碳纤维复合材料超声振动辅助RTM工艺的浸润特性

研究了织物类型、纤维体积分数和超声振动对树脂在碳纤维织物中流动特性的影响规律,设计了超声振动辅助RTM工艺过程中单向渗透率测量装置,开展了16组渗透率测试实验,并结合COMSOL软件仿真分析了织物中的树脂流动特性。研究表明,在相同纤维体积分数水平下,斜纹编织物的纤维束间隙通道比平纹织物的更宽,2/2斜纹编织织物渗透率比平纹织物提高了约21.5%。纤维体积分数与织物渗透率呈负相关,其函数关系与半经验公式Kozeny-Carman(KC)方程吻合较好。树脂流动过程中加入超声振动,其超声空化效应、加速度效应和微射流效应作用于纤维丝束表面,提高了织物渗透率约58.2%。有限元仿真模拟了椭圆形和近矩形纤维束截面设计的织物模型的流动过程,结果发现近矩形纤维束截面高流速区域范围更广,流体向纤维布夹层浸渍的速度分量更大。超声作用于织物纤维可能带动纤维丝束蠕动,使纤维束截面趋于近矩形状,从而提高了树脂对纤维织物的浸润性。上述研究结果对优化碳纤维复合材料成型工艺和成型性能具有一定的指导意义。      

碳纤维复合材料的微波反射特性研究

研究了各种铺层（０°、０°／９０°、±３０°、±４５°、±６０°）方式碳纤维复合材料（ＣＦＲＰ）的皮反射特性。结果表明,单向纤维铺层ＣＦＲＰ的反射率与纤维方向及层板厚度有关;交叉铺层ＣＦＲＰ的反射率很大,但比金属略小,喷涂了防雷击层的单向纤维铺层ＣＦＲＰ,电性能基本上各向员性;喷涂了防雷击层的０°、±４５°、０°／９０°ＣＦＲＰ的反射率比喷涂前有所降低。     

Two practical methods for improving the long-term stability of thephotoelastic optical fiber pressure sensor

The differential approach of photoelastic optical fiber pressure sensor (POFPS) has been published. However, the experimental aspects of this sensor were little involved in it. Two practical methods are described to investigate this subject. First, the discordance of expansion coefficient, between the cladding steel and the graded-index (GRIN) lens, is considered by using indium steel cladding instead of the conventional stainless steel cladding. Then an experimental setup is designed to make the infrared light intensity distribution observable by using a CCD camera. Practical tests prove that these two practical methods and the design of the differential approach have improved the long-term stability of POFPS     

表面改性和复合工艺对金属纤维/聚合物复合材料性能的影响

以不锈钢纤维为导电填料,分别与ABS和PP复合,制得了电磁屏蔽用导电高分子复合材料。考察了表面改性和复合工艺对金属纤维／聚合物复合材料性能的影响。结果表明,用不同表面处理剂处理不锈钢纤维后,随纤维表面张力增加,复合材料的电阻率增加。使用母料法工艺可以有效地改善金属纤维在聚合物基体中的分散,从而提高复合材料的导电性能和电磁屏蔽性能。