A Novel Multiscale Reinforcement by In-Situ Growing Carbon Nanotubes on Graphene Oxide Grafted Carbon Fibers and Its Reinforced Carbon/Carbon Composites with Improved Tensile Properties

In-situ growing carbon nanotubes （CNTs） directly on carbon fibers （CFs） always lead to a degraded tensile strength of CFs and then a poor fiber-dominated mechanical property of carbon/carbon composites （C/ Cs）. To solve this issue, here, a novel carbon fiber-based multiscale reinforcement is reported. To synthesize it, carbon fibers （CFs） have been first grafted by graphene oxide （GO）, and then carbon nanotubes （CNTs） have been in-situ grown on GO-grafted CFs by catalytic chemical vapor deposition. Characterizations on this novel reinforcement show that GO grafting cannot only nondestructively improve the surface chemical activity of CFs but also protect CFs against the high-temperature corrosion of metal catalyst during CNT growth, which maintains their tensile properties. Tensile property tests for unidirectional C/Cs with different preforms show that this novel reinforcement can endow C/C with improved tensile properties, 32% and 87% higher than that of pure C/C and C/C only doped with in-situ grown CNTs. This work would open up a possibility to fabricate multiscale C/Cs with excellent global performance.

Effect of Rare Earths on Tribological Properties of Carbon Fibers Reinforced PTFE Composites

Carbon fibers （CF） were surface treated with air-oxidation and rare earths （RE）, respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE （CF/PTFE） composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.

Synchronously constructing networked Si_(3)N_(4) nanowires and interconnected graphene inside carbon fiber composites for enhancing mechanical, friction and anti-ablation properties

Carbon fiber(C_(f))reinforced pyrolytic carbon(PyC)composites simultaneously possessing robust mechanical strength,excellent friction performances and outstanding anti-ablation properties are demanded for advanced aerospace applications.Efficient architecture design and optimization of composites are promi-nent yet remain high challenging for realizing the above requirements.Herein,binary reinforcements of networked silicon nitride nanowires(Si_(3)N_(4) nws)and interconnected graphene(GE)have been successfully constructed into C f/PyC by precursor impregnation-pyrolysis and chemical vapor deposition.Notably,net-worked Si_(3)N_(4) nws are uniformly distributed among the carbon fibers,while interconnected GE is firmly rooted on the surface of both networked Si_(3)N_(4) nws and carbon fibers.In the networked Si_(3)N_(4) nws and interconnected GE reinforced C_(f)/PyC,networked Si_(3)N_(4) nws significantly boost the cohesion strength of PyC,while GE markedly improves the interface bonding of both Si_(3)N_(4) nws/PyC and fiber/PyC.Benefiting from the synergistic reinforcement effect of networked Si_(3)N_(4) nws and interconnected GE,the C_(f)/PyC have a prominent enhancement in mechanical(shear and compressive strengths increased by 119.9% and 52.84%,respectively)and friction(friction coefficient and wear rate reduced by 25.40% and 60.10%,respectively)as well as anti-ablation(mass ablation rate and linear ablation rate decreased by 71.25% and 63.01%,respectively).This present strategy for networked Si_(3)N_(4) nws and interconnected GE reinforced C_(f)/PyC provides a dominant route to produce mechanically robust,frictionally resisting and ablatively resistant materials for use in advanced aerospace applications.

Effects of Fiber Surface Pretreatment and Composite Posttreatment on Mechanical Properties of 2D⁃Cf/Phosphate Geopolymer Matrix Composites

Geopolymers are an important class of materials with potential applications because of their heat resistance,flame resistance,environmental friendliness,and possibilities of being transformed into ceramic matrix composites at low cost.However,the low mechanical properties as well as the intrinsic brittleness limit their technological implementations,and it is necessary to enhance the mechanical properties of geopolymers by adopting various kinds of reinforcements.In this work,therefore,two⁃dimensional continuous carbon fiber(Cf)reinforced phosphate⁃based geopolymer composites(Cf/geopolymer)were prepared through ultrasonic⁃assisted impregnation method.Effects of acetone treatment and high⁃temperature treatment on the properties of Cf/geopolymer composites were studied by X⁃ray photoelectron spectroscopy(XPS),X⁃ray diffraction(XRD),and scanning electron microscopy(SEM).Results of the study proved that acetone treatment plays a key role in ameliorating the interfacial interaction between Cf and phosphate matrix,which can thus enhance the mechanical properties of Cf/geopolymer composites.The Cf/geopolymer composites prepared by acetone⁃treated Cf had a flexural strength of 156.1 MPa and an elastic modulus of 39.7 GPa in Y direction.Moreover,an additional Sol⁃SiO2 re⁃impregnation treatment could further enhance the mechanical properties of the acetone⁃treated Cf/geopolymer composites by repairing the cracks and filling the pores.The results in this paper not only provide insights into the surface modification of Cf,but also report a facile and low⁃cost preparation route for Cf/geopolymer composites with potential applications in aerospace and defense technology.

Interconnected Ni(OH)_(2)and polyether amine on carbon fiber surface for simultaneously improving interfacial adhesion of epoxy composites and electrochemical properties

Interconnected Ni(OH)_(2)nanoflakes and polyether amine(PEA)were deposited on carbon fiber tows via a facial and effective process of chemical bath deposition and dip coating.Based on this,a win–win benefit of simultaneously improvements in interfacial shear strength(IFSS)of carbon fiber/epoxy composites and the electrochemical activity has been achieved.Compared with CF and CF-Ni(OH)_(2)composites,the IFSS of CF-Ni(OH)_(2)-PEA/epoxy composite respectively increased 7.9%and 45.4%,which was put down to the covalent bonding of Ni(OH)_(2)-PEA coating with fiber and epoxy matrix,as well as the effective stress transfer by the uniform honeycomb structure of Ni(OH)_(2).In aqueous KOH electrolyte,the CF-Ni(OH)_(2)-PEA electrode presented the maximum specific capacitance of 689.98 F·g^(-1)at 5 m V·s^(-1),572.28 F·g^(-1)at a current density of 0.5 A·g^(-1)due to the strong adhesion of carbon fiber with Ni(OH)_(2)by PEA,the reservation of the threedimensional hollow honeycomb structure of Ni(OH)_(2)for easy ion-transport and–NH_(2)functional groups from PEA for providing more active sites.The excellent performance of CF-Ni(OH)_(2)-PEA reinforcement demonstrates its promising potential for application in high performance composites with integrated structure and function,which shows great advantages in various fields of aerospace,energy,electronics,automobile,civil engineering,sports,etc.

Fabrication of Short Carbon Fiber Reinforced AZ91D Alloy by Infiltration-Extrusion Integrated Technique

Short carbon fiber reinforced AZ91D alloy (Csf/AZ91D) was fabricated by the infiltration-extrusion method. The short carbon fiber preform was infiltrated with melted AZ91D alloy under the assistant of gas pressure. The extrusion processing was applied following the infiltration processing directly. The tensile property and microstructure of the Csf/AZ91D and that of the die-casting and extruded AZ91D alloy was compared. The results show that the short carbon fiber reinforced AZ91D alloy present excellent tensile property. The tensile strength and modulus of elasticity of Csf/AZ91D is about 50% and 18% higher than that of cast AZ91D alloy, respectively. The elongation to fracture of Csf/AZ91D is about 50% lower than that of AZ91D alloy.

碳酸钙晶须混杂聚乙烯纤维增强水泥基复合材料力学性能研究

为研究碳酸钙晶须掺量对聚乙烯纤维增强水泥基复合材料(PE-ECC)力学性能及微观结构的影响,设计了4组不同碳酸钙晶须掺量的PE-ECC试件,对其进行抗压性能试验、抗拉性能试验、三点弯曲断裂性能试验,并使用XRD、SEM、NMR技术对其微观结构进行研究。结果表明,碳酸钙晶须对PE-ECC有增强增韧作用,随着碳酸钙晶须掺量增加,这种增强增韧作用呈先增大后减小的趋势,当碳酸钙晶须掺量为1%(体积分数)时,PE-ECC的抗压性能、拉伸性能、断裂性能提升最佳。适量的碳酸钙晶须能填充基体,减少少害孔及多害孔数量,改善孔隙结构。

多维碳材料/聚氨酯复合材料的制备、力学性能及功能性

文中采用异氟尔酮二异氰酸酯对氧化石墨烯(GO)和羟基碳纳米管(OH-MWCNTs)混合碳材料接枝改性,制备出NCO官能团接枝的MWCNTs-g-GO高活性多维碳材料及新型聚氨酯复合材料。研究了MWCNTs-g-GO多维碳材料对力学性能、老化行为和导电性的影响。由X射线衍射分析得出,改性后混合碳材料中GO的层间距由0.87 nm扩大到1.71 nm,碳纳米管缠结程度明显降低,有效提升了碳纳米材料的分散性;随着多维MWCNTs-g-GO含量的增加,对聚氨酯进行了力学性能测试,其硬度、定伸强度逐渐增加,断裂伸长率单调降低,拉伸强度则先增大后减小;当其含量为0.05%时,拉伸强度较空白样提高23%,增大到48.7 MPa;老化150℃×5 d后,衰减率约为26.3%;当含量为0.20%时,电导率约为6.12×10^(-4) S/cm,是空白样的76倍。多维碳纳米材料较单一碳材料对聚氨酯表现出优异的增强、抗热氧和导电等作用。

连续碳纤维增强聚酰胺6复合材料拉板的制备与性能研究

采用连续碳纤维增强聚酰胺6预浸料通过缠绕-模压成型工艺制备复合材料拉板。采用自制的拉伸工装对复合材料拉板的拉伸性能进行评测,研究其破坏形式及失效机制。研究发现,增加模压成型压力可以减少复合材料中的孔隙,使孔隙缩小,减少内部缺陷,使结构更致密,提高拉板的拉伸强度。未加套环拉板拉伸破坏位置在其端部,外层纤维被拉塌劈裂,只有内层纤维一直起作用直至被拉断,拉伸强度较低。加套环拉板拉伸破坏位置是在侧面靠近轴套位置,纤维是拉断破坏,断裂截面比较平齐;整个拉伸过程中,套环的横向约束使所有纤维都能够很好地发挥抗拉作用,使其具有较高的拉伸强度。

基于上浆处理的碳纤维/聚丙烯纤维毡复合材料的制备及性能研究

碳纤维/热塑性树脂基复合材料因其综合性能好、耐变形、可循环利用等优异性能在复合材料领域拥有良好前景,界面作为两相的过渡区域,起到应力传递作用,对复合材料的力学性能有重要影响。通常采用上浆剂使碳纤维表面改性,从而提高界面结合能力。本文针对一种碳纤维/聚丙烯混合毡进行上浆,采用模压成型制备复合材料。通过透气性、透光性测试分析了上浆均匀性和对混合毡结构的效果,通过拉伸、弯曲及冲击试验研究了上浆对复合材料力学性能的影响效果,并分析了上浆剂的作用机理。结果表明,上浆后,复合材料的拉伸强度提高了22.52%,弯曲强度提高了7.57%,冲击强度提高了39.07%。

纳米微晶碳纤维改性复合材料的强度与力学性能研究

对碳纤维进行硅烷化改性处理,考察了硅烷化改性对碳纤维性能的影响。结果表明,改性后纤维素的长度和宽度都未发生明显变化;改性碳纤维的单丝拉伸强度会随着硅烷化纳米微晶纤维素(AMEO-NCC)含量提升而先增后减,单丝拉伸强度最大值在硅烷化纳米微晶纤维素质量分数为0.3%时取得(3.74 GPa)。硅烷化纳米微晶纤维素改性碳纤维复合材料的室温力学性能相较去除上浆剂碳纤维复合材料和涂覆环氧树脂的碳纤维复合材料都有不同程度提升,且硅烷化纳米微晶纤维素改性碳纤维复合材料的层间剪切强度、弯曲模量和弯曲强度会随着硅烷化纳米微晶纤维素含量增加而先增后减,最大值在硅烷化纳米微晶纤维素质量分数为0.3%时取得。

碳纤维复合板叠层铆接参数优化与性能测试及工艺对比

为了提升建筑工程用纤维复合材料的拉伸性能,设计了不同叠层顺序、铺层层数的碳纤维复合板,并对比了传统工艺和新型工艺下碳纤维复合板的拉伸性能和断口形貌。结果表明,碳-铝复合板的最大拉伸载荷(2.22 kN)明显高于铝-碳复合板(0.67 kN),且相较于铝-碳复合板,断裂后碳-铝复合板的位移相对更大;随着铺层层数增加,碳-铝复合板的拉剪面积逐渐增加,拉伸强度呈现先增加后减小的趋势,在铺层层数为16时取得拉伸强度最大值。传统工艺下碳纤维复合板的最大拉伸载荷为1.53 k N,而新型工艺下碳纤维复合板的拉伸载荷为2.22 kN,约为传统工艺下碳纤维复合板最大载荷的1.45倍。

石墨烯改性环氧树脂/碳纤维复合材料拉伸性能的研究

通过H2SO4/HNO3混酸酸化石墨烯,并用硅烷偶联剂KH-560接枝酸化的石墨烯,然后将处理好的石墨烯均匀的分散在环氧树脂中,制备高性能的环氧树脂/碳纤维复合材料。通过红外光谱(FTIR)、热失重(TG)、透射电子显微镜(TEM)等分析方法对处理的石墨烯的表面官能团及表面形貌进行表征,用DCW-7拉伸试验机对所制得的复合材料进行测量。结果表明:酸化的石墨烯表面成功地接枝上了一定量的硅烷偶联剂KH-560,在树脂体系中添加2%的硅烷偶联剂KH-560处理的石墨烯的复合材料的拉伸强度提高了10.7%,断裂强力提高了10.4%。

石墨烯改性对环氧树脂/碳纤维复丝拉伸性能的影响

采用直接分散法和上浆剂法分别制备了环氧树脂/碳纤维复丝,通过红外光谱、分光光度法等分析方法对处理的石墨烯的表面官能团及表面形貌进行表征,借助扫描电子显微镜对碳纤维表面进行微观形貌观察,研究了石墨烯改性对环氧树脂/碳纤维复丝界面性能的影响。结果表明:石墨烯表面成功地接枝了硅烷偶联剂KH-560;接枝硅烷偶联剂KH-560的石墨烯的环氧树脂/碳纤维复丝的拉伸性能优于未经改性的石墨烯的复丝;上浆法制得的环氧树脂/碳纤维复丝的拉伸性能优于分散法制得的复丝的拉伸性能;上浆剂法制备的石墨烯改性的环氧树脂/碳纤维复丝的断裂强力比未经过改性的未上浆的复丝的提高了48.6%,拉伸强度提高了30.4%,断裂伸长率提高了90.9%。

碳纤维毡增强聚丙烯复合材料的力学性能

将长碳纤维开松针刺成毡,并通过双钢带压机制备了碳纤维毡增强聚丙烯复合材料(CFRPP),考察了碳纤维长度、含量、纤维毡的针刺及针刺类型、基体改性等因素对复合材料力学性能的影响,并对复合材料断面进行了扫描电镜观察以分析CFRPP界面结合情况。结果表明:实验范围内的纤维长度对碳纤维增强复合材料的力学性能基本没有影响;复合材料综合力学性能最佳的碳纤维质量分数约为30%;碳纤维毡经三角形针针刺后复合材料的拉伸性能得到较大幅度提高;相容剂马来酸酐接枝聚丙烯(MPP)能够改善碳纤维与聚丙烯的界面结合,提高复合材料的力学性能,其最适宜的相容剂MPP的质量分数约为20%;将长度为80mm的碳纤维用三角针刺成毡后,以MPP改性的聚丙烯(wMPP=20%)浸渍制备得到碳纤维质量分数为30%的复合材料,拉伸强度为203.3 MPa,拉伸模量达16.6GPa,弯曲强度为223.2 MPa,弯曲模量达到12.0GPa,缺口冲击强度为752.2J/m。

纳米碳酸钙浸渍改性工艺对竹塑复合材料拉伸性能的影响

为探寻竹纤维表面改性技术应用于植物纤维增强热塑性聚合物复合材料中的理论依据,用硫酸盐法制取竹纤维,以聚丙烯(PP)为基体,竹纤维为增强相,采用平压成型工艺制备竹纤维/PP复合材料,探索了纳米碳酸钙(CaCO_3)浸渍改性工艺对复合材料拉伸性能的影响,并利用场发射环境扫描电镜、力学测试机对其断口形貌和力学性能进行表征。结果表明:在温度25℃,搅拌速度500r/min的条件下,当纳米CaCO_3添加量为1.00×10-2 g/mL,分散剂EDTA-2Na添加量为8.50×10-4 g/mL,浸渍混合时间为25min时,竹纤维/PP复合材料的拉伸性能较优。

碳纤维强度的统计特性及对复合材料线芯力学性能的影响

测试了国产T300级碳纤维的单丝和复丝拉伸强度,并用Weibull分布来描述碳纤维单丝平均拉伸强度。采用拉挤工艺制备出国产碳纤维复合线芯,测试了国产碳纤维复合线芯的弯曲强度和短梁剪切强度性能。结果表明:国产T300级碳纤维单丝拉伸强度性能达到东丽T300碳纤维水平,且分散性更小;复丝强度略低。国产T300级碳纤维集束性较差,在拉挤抽纱过程中,容易夹纱和起毛。在纤维体积含量基本相同情况下,国产T300级碳纤维复合线芯力学性能与东丽T700碳纤维复合线芯力学性能相差不大。

软硬混编预制体增强沥青基4D-C/C材料的拉伸破坏行为

以X-Y平面依次铺设炭纤维束、Z向穿插炭棒的4D软硬混编为预制体,采用沥青液相常压、高压浸渍/炭化-石墨化循环致密工艺制备4D-C/C复合材料。通过该材料Z向(炭棒方向)的拉伸实验,测定其拉伸性能和力学行为,并采用SEM分析试样表面及断口形貌。结果表明:宏观上拉伸试样以炭棒整体拔出的形式破坏;细观尺度上,试样表面形成了与载荷方向垂直的贯穿性裂纹,裂纹以2 mm左右的距离呈等间距分布;材料进一步的破坏过程中,基体裂纹在X-Y向纤维束中呈线性扩展,快速分割了基体材料,使4D-C/C复合材料的拉伸破坏演变为1D-C/C复合材料的破坏模式,由于炭棒与基体炭界面结合弱,炭棒以拔出方式失效和破坏。

基体改性对碳纤维增韧碳化硅复合材料结构与性能的影响

采用化学气相浸渗法对2DC/SiC复合材料进行基体改性,制备了二维碳纤维增韧碳–碳化硅二元基复合材料(twodimensionalcarbonfiberreinforcedC–SiCbinarymatrixcomposites,2DC/C–SiC)。2DC/C–SiC复合材料的基体为热解碳和碳化硅交替叠层的多层基体。研究了2DC/C–SiC复合材料的微观结构,比较了2DC/SiC复合材料和2DC/C–SiC复合材料的力学性能及断口形貌。结果表明:2DC/C–SiC复合材料可在基本保持2DC/SiC复合材料抗弯强度的基础上,其断裂韧性得到显著提高。基体改性的效果明显。纤维的逐级拔出是断裂韧性提高的原因。

混杂比对碳/芳纶纤维混杂纬编双轴向多层衬纱织物增强复合材料力学性能的影响

利用层内混杂的方式制备碳/芳纶纤维混杂纬编双轴向多层衬纱织物,通过对材料进行拉伸、三点弯曲等实验研究该织物增强复合材料的力学性能及混杂比对其力学性能的影响。结果表明,按照一定的混杂比加入芳纶纤维后复合材料的拉伸性能提高,表现出积极的混杂效应。由于延伸性好的芳纶纤维的加入,使复合材料的拉伸断裂伸长率明显提高,材料破坏模式出现了完全脆性断裂模式(C12材料破坏形式)和“扫帚”形纤维断裂模式(C8A4,C6A6材料破坏形式)。此外,按照一定的混杂比加入芳纶纤维也有效改善了碳纤维增强复合材料的破坏韧性,碳/芳纶纤维混杂MBWK织物增强复合材料的弯曲强度和弯曲模量随混杂比的提高而呈下降趋势,当复合材料中芳纶含量从42%(体积分数,下同)(C6A6)到59.2%(C4A8)的变化过程中,弯曲强度和弯曲模量的降低率较高。0°试样在混杂比为59.2%(C4A8)时,弯曲挠度最大,达到7.49 mm,远高于纯芳纶纤维或纯碳纤维增强的复合材料。所有90°混杂复合材料试样的弯曲挠度均高于纯芳纶纤维或纯碳纤维增强的复合材料,表现出积极的混杂效应。