Influence of oxygen and nitrogen plasma treatment on polyethylene terephthalate (PET) polymers

In this paper we present surface modification of polyethylene terephthalate (PET) polymer, which is commonly used as synthetic vascular graft. Surface modification was made by oxygen and nitrogen plasma at different treatment times. Plasma was created by means of an RF generator at a discharge power of 200 W and gas pressure fixed at 75 Pa. The surface of PET polymer was modified in order to achieve improved attachment of fucoidan, which is a bioactive coating with antithrombogenic properties. In our study we analysed chemical modification of plasma treated surfaces by X-ray photoelectron spectroscopy (XPS), while the changes in morphology and surface roughness were observed with atomic force microscopy (AFM). Our results indicate that attachment of fucoidan is improved by oxygen plasma treatment, especially due to surface roughening.     

Influence of plasma treatment on CNT absorption of cotton fabric and its electrical conductivity and antibacterial activity

In this study, effect of plasma pretreatment on the absorption of carboxilated carbon nanotubes (CNTs) on the surface of cotton fabrics was investigated. Treated samples were characterised using a Raman spectrophotometer. Also, the morphological properties of samples were studied using a scanning electron microscope. Electrical resistance and interactions between CNTs and plasma-treated cotton functional groups at the surface were also evaluated. Antibacterial activity of cotton fabric when modified by low temperature plasma and stabilised with CNTs was also investigated. Results showed a uniform coating of CNTs on the plasma-treated cotton fabric and it was found that the plasma treatment is effective on improving CNTs absorption by cotton fabric. Generally, cotton fabric characterisation, such as antibacterial activity and electrical conductivity, after plasma treatment and loading CNT are improved.     

Effect of air plasma treatment on mechanical and tribological properties of PBO fabric composites

Friction and wear behavior of one-step or two-step air plasma treated and untreated PBO fabric composites has been evaluated in a pin-on-disc friction and wear tester. Tensile property of impregnated fabric and bond property between fabric and metallic substrate have also been studied. A comparison has been made between untreated and plasma treated fibers by using XPS, FTIR, FESEM and SEM. The results indicated that, air plasma treatment could increase the friction coefficient but decrease the wear rate of the PBO fabric composites. The most suitable condition of plasma treatment was 50 W and 15 min. After two-step plasma treatment, the tensile strength of the PBO fabric was decreased by 40%. While the antiwear property and bonding strength of the PBO fabric composites could be improved by 40–67% and 64%, respectively, which was due to the improvement of the bond property among the fiber, the adhesive and substrate.     

Influence of graphite filler on two-body abrasive wear behaviour of carbon fabric reinforced epoxy composites

The influence of graphite filler additions on two-body abrasive wear behaviour of compression moulded carbon–epoxy (C–E) composites have been evaluated using reciprocating wear unit and pin-on-disc wear unit under single pass and multi-pass conditions respectively. The carbon fabric used in the present study is a plain one; each warp fiber pass alternately under and over each weft fiber. The fabric is symmetrical, with good stability and reasonable porosity. Abrasive wear studies were carried out under different loads/abrading distance using different grades of SiC abrasive paper (150 and 320 grit size). Graphite filler in C–E reduced the specific wear rate. Further, the wear volume loss drops significantly with increase in graphite content. Comparative wear performance of all the composites showed higher specific wear rate in two-body wear (single-pass conditions) compared to multi-pass conditions. Further, the tribo-performance of C–E indicated that the graphite filler inclusion resulted in enhancement of wear behaviour significantly. Wear mechanisms were suggested and strongly supported by worn surface morphology using scanning electron microscopy.     

等离子处理碳纤维织物复合材料的摩擦学性能

将碳纤维织物浸渍-涂层酚醛-缩醛粘结剂树脂,加压固化后制备出碳纤维织物复合材料.分析了摩擦磨损表面和经等离子体处理后碳纤维织物化学组成的变化,研究了摩擦磨损性能、拉伸性能和粘结性能.结果表明,碳纤维织物的磨损分为严重磨损和稳定磨损两个阶段,其中严重磨损阶段的磨损量占了总磨损量的87%.经过等离子体处理后,在碳纤维织物的表面产生了许多活性基团如羰基、羧基、酯基,表面活性元素的含量明显增多;碳纤维织物的浸润性增大,提高了其与粘结剂的结合强度和结合量,增强了织物纤维束间的结合力;固化后与粘结剂构成很好的整体材料,增强了纤维束抗变形和抗断裂能力,使载荷和摩擦力可以平均的分配在纤维上,避免应力集中,从而提高了碳纤维织物复合材料的摩擦学性能和力学性能.     

Fabrication and characterization of three-dimensional cellular-matrix composites reinforced with woven carbon fabric

A low-density three-dimensional cellular-matrix composite reinforced with woven carbon fabric (3DCMC), was fabricated by means of a pressure-quenching molding technique with nitrogen gas as the blowing agent. Epoxy resins in the interstices of yarns in the 3DCMC samples were vacated during the foaming process and needle shaped voids were also generated between fibers in yarns. The average density of the 3DCMC samples was about 10³ kg/m³, and their density reduction was 28–37% compared with a regular matrix composite with the same preform. The 3DCMC has 32–42% higher specific tensile strength, 14–37% greater specific tensile modulus, a lower specific flexure strength but 35% higher specific tangent modulus in 3-point bending, a 30–40% higher specific impact energy absorption at an impact velocity around 120 m/s and a similar specific energy absorption at about 220 m/s. Meanwhile, the 3-point bending and impact test results of 3DCMC showed that they have different fracture mechanisms from that of 3DRMC.     

碳纤维织物复合材料螺柱-柱销连接结构研究

在综合分析各种复合材料连接结构的基础上,针对复合材料构件高承载轴向连接要求,提出了织物复合材料螺柱-柱销连接结构,并实验研究了织物复合材料的挤压强度,测试了螺柱-柱销连接结构的承载能力.试验结果表明,织物复合材料的最大挤压强度为887 MPa,高于0/90纤维层板复合材料的挤压强度;织物复合材料螺柱-柱销连接结构在薄壁复合材料构件的轴向连接方面,与传统的金属端框连接形式相比,接头质量效率高,成型工艺简便,具有较大的应用潜力.     

Compaction of thick carbon/phenolic fabric composites with autoclave method

Carbon/phenolic composites are used in the nozzle parts of solid rocket motors due to their heat-resisting, ablative, and high strength characteristics, which are required to endure the high temperature and pressure of combustion gas passing through the nozzle. But the thick axi-symmetric structure of the composite nozzle induces high thermal residual stresses due to the large difference of coefficient of thermal expansion (CTE) between the in-plane and the out-of-plane. In this work, in order to reduce the through-thickness CTE and the void content, a compression in the thickness direction was applied to the composite prepreg by a compressive jig during manufacturing of composite to supplement the low autoclave pressure. The through-thickness CTE of the fabric composite was calculated by a compaction model and compared with the measured one by thermo-mechanical analysis. The through-thickness CTE changed drastically with respect to the compaction amount, and the void content of the carbon/phenolic fabric composite laminate showed different characteristics from the ordinary fabric laminates with respect to the autoclave pressure and the jig pressure.     

斜纹机织碳纤维/环氧树脂复合材料性能及其在电动汽车轻量化设计中的应用

采用均质法和单胞有限元法, 研究了斜纹机织碳纤维/环氧树脂复合材料的三维本构模型, 并应用于轻量化电动汽车结构的设计计算中。通过光学显微镜观测获得T300碳纤维/环氧树脂复合材料层合板细观结构几何参数, 依据参数建立了代表体积元的几何模型; 结合有限元分析方法与层合板理论对代表体积元模型进行受力分析, 获得了复合材料三维本构模型参数, 并运用单向拉伸与三点弯曲物理试验对所建立的本构模型进行了验证; 通过二次开发, 把该三维本构模型用于轻量化电动汽车结构件的设计中, 并根据汽车安全测试标准对所设计的结构进行了强度校核。研究表明: 运用所建立的三维材料本构模型进行的仿真实验结果与真实拉伸和弯曲试验结果相吻合, 误差分别为4.04%和7.79%, 可用于轻量化结构的设计; 研究开发的电动汽车, 轻量化效果明显, 在满足车身强度要求下整车质量减轻了12%。      

Influence of ultrasonic treatment on the characteristics of epoxy resin and the interfacial property of its carbon fiber composites

To enhance the interfacial property between a carbon fiber and epoxy matrix, an ultrasonic technique was used to treat the resin liquid and the impregnated fibers respectively. The effects of the treatments on the characteristics of the resin system and the fiber surface, as well as fiber/matrix interfacial bonding strength, were analyzed and discussed. The results indicated ultrasonic treatments significantly decreased the viscosity and surface tension of the resin system, and increased the wettability and the oxygen content of the fiber surface due to the ultrasonic cavitation effects. Microbond tests revealed much more increase of interfacial shear strength when the ultrasound was applied to the impregnated fibers, and combination failures of interface and matrix layer were observed from the pulled-out fiber surface.     

Enhancing the adhesive wear performance of polyetherimide composites through nano-particle treatment of the carbon fabric

Rare earth compound Ytterbium fluoride (YbF₃) in nano-size (40–80 nm) was employed for surface treatment of carbon fabric (CF) to improve its wettability with polyetherimide matrix. Composites were developed based on untreated and surface-treated CF with three doses, 0.1, 0.3, and 0.5 wt%, of YbF₃ in ethyl alcohol suspension. The composites were analyzed for interlaminar shear strength (ILSS). Improvement in ILSS was observed for treated fabric reinforced composites and it was maximum (61%) for 0.3 wt% dose of YbF₃. The adhesive wear performance of composites was evaluated by sliding a pin of composite against mild steel disc under varying loads (200–600 N). The treated fabric composites exhibited lower coefficient of friction (μ) and higher wear resistance (W _R). ILSS and W _R showed good linear correlation. Both properties were highest for 0.3% YbF₃ dosing. Increased roughness of fiber surface and adhesion of nano-particles on the fiber surface was observed in scanning electron microscopic (SEM) studies. SEM studies of worn surfaces of composites were performed to understand wear mechanisms. Atomic force microscopic studies indicated substantial increase in roughness value of CF.     

碳纤维-尼龙6混编织物复合材料的制备及性能

为了探究合适的碳纤维表面处理方法,改善碳纤维-尼龙6织物复合材料界面结合效果,提高复合材料的力学性能,通过混编的方式制备碳纤维-尼龙6预制件,将预制件浸泡在不同浓度的醇溶尼龙无水乙醇溶液中,最后将预制件通过热压成型,制备碳纤维织物-尼龙6复合材料。采用万能拉伸试验机、SEM、TGA、DSC、XRD分析碳纤维-尼龙6复合材料的力学性能、微观形貌、耐热性能、结晶度及晶型变化。结果表明:将预制件在浓度为1wt%的尼龙溶液处理后,并采用1℃/min的降温速率制备的碳纤维-尼龙6织物复合材料力学性能最佳,抗拉强度、弹性模量、弯曲强度、弯曲模量、冲击强度分别为449.32 MPa、5.32 GPa、657.67 MPa、44.08 GPa、138.42 kJ/m2。纤维拔出后,单根碳纤维表面附着部分尼龙基体,碳纤维与尼龙基体形成了良好的界面层。碳纤维-尼龙6织物复合材料的起始分解温度较尼龙6纤维提高了13℃,耐热性有所增强,尼龙6树脂主要以α晶型存在,结晶较为完善。      

Surface designing of carbon fabric polymer composites with nano and micron sized PTFE particles

The new technique to tailor carbon fabric-polyethersulphone (CF-PES) composite surface with polytetrafluoroethylene (PTFE) nano particles; to improve wear performance has been reported. Cold remote nitrogen oxygen plasma (CRNOP) treatment was employed to alter the CF surface to promote fiber/matrix adhesion and further; inter laminar shear strength and wear performance of the composites. The atomic force microscopy and high resolution transmission microscopy; studies confirms the topographical modification on the fiber surface due to CRNOP treatment. The dipper ridges and perforations introduced on the fiber surface were analyzed with field emission scanning electron microscopy. The PTFE particles film formation on the worn composite surface was supportively analyzed by Raman spectroscopy and energy dispersive X-ray techniques. The topographical smoothening and rolling effect during the wearing of surface designed composites with PTFE nano particles; endorse to enhance its sliding wear properties and life.     

Fatigue and post-fatigue behaviour of carbon/epoxy non-crimp fabric composites

This paper focuses on the static, fatigue and post-fatigue tensile properties of a biaxial carbon/epoxy non-crimp fabric composite. In a series of quasi-static tensile tests, the stress–strain level where damage initiates was determined. This stress level was then used as the maximum stress level in tensile–tensile fatigue tests in the fibre direction. It was found that in fibre direction, this load level can be considered safe for fatigue up to very high cycle numbers. The damage evolution during the tests was monitored at certain cycle times with X-ray radiography. The post-fatigue residual static tensile properties were determined after different numbers of cycles. A series of tensile–tensile fatigue tests at various higher stress levels allowed for the fatigue life curves to be constructed in each of the four testing directions. This revealed that the damage initiation load level is well below the practical fatigue limit of the material.     

Effect of carbon fabric whiskerization on mechanical properties of CC composites

Carbon fabric whiskerization via a direct, non-catalytic SiC whisker formation was investigated as a method to increase the shear and transverse properties of carbon-carbon (C---C) composites. The whiskers were produced via a SiO gas reaction with the carbon fiber surface. A variable level of whisker's population density was achieved by varing the whiskerization conditions. The flexure strength of phenolic resin-derived C---C composites made with the whiskerized fabric was found to be decreasing with increasing the extent of the fiber whiskerization. A 300% increase in the interlaminar strength (ILT) combined with a 250% increase in the interlaminar shear strength (ILS) was found in the case of the composites made with a low whiskerized fabric.     

Influence of CVI treatment of carbon fibers on the electromagnetic interference of CFRC composites

Short carbon fibers were treated at temperatures around 1100 °C in a furnace through chemical vapor infiltration technology. The fiber surface was observed by scanning electron microscopy. The reflectivity of electromagnetic radiation by the composites that were reinforced by surface-treated carbon fibers and by as-received ones was measured in the frequency range of 8.0–18.0 GHz. The reflectivity for different carbon fiber contents of 0.2%, 0.4%, 0.6% and 1.0 wt% was investigated. Results showed that the reflectivity of the composites that were reinforced by untreated carbon fibers tended to increase with the increasing fiber contents. The minimum reflectivity was −19.3 dB, far less than −10 dB, when the fiber content was 0.4% and there were wave-absorbing properties. However, after surface treatment, the minimum reflectivity was −8.1 dB for the same fiber content of 0.4%, indicating significant wave-reflecting properties. The achieved reflectivity values after surface treatment were generally greater than those without treatment.     

炭膜制备及其高效氧氮分离性能

通过论述炭膜的制备方法及其关键影响因素，系统总结了炭膜的氧氮分离性能，并将其与高性能聚吡咙膜和聚苯胺膜进行了比较，提出了今后的发展方向。指出炭膜具有优异的氧氮分离性能，其氧氮分离因子一般为10以上，最高可达36。聚酰亚胺基和聚吡咙基炭膜均表现出较好的综合氧氮分离性，大大突破了富氧膜材料的Robeson上限，位于极具吸引力的商业化区域，在空气分离中显示出了极大的应用潜力和工业化前景。     

Functionalization of single-walled carbon nanotubes by citric acid/oxygen plasma treatment

A safe and simple method of functionalizing single-walled carbon nanotubes (SWCNTs) has been developed, that significantly increases their dispersibility in water. SWCNTs in pure ethanol are treated with a supersonic homogenizer and dried. Then they are wetted with weak citric acid solution. Finally an RF (13.56 MHz) citric acid/oxygen plasma reaction is carried out under optimum conditions. As a result, hydrophilic functional groups attach onto the SWCNT surfaces, which enhance their dispersibility in water. The attachment of functional groups is identified by the FT-IR spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The dispersibility and dispersion stability are studied by the precipitation tests, UV-visible spectroscopy, and transmission electron microscopy. These functionalized SWCNTs are expected to be used in various applications.     

碳纤维形貌结构对其电化学氧化行为及其复合材料界面性能的影响

通过调控原丝工艺,制备得到形貌结构不同、力学性能相近的PAN基碳纤维(CF),用以模拟碳纤维表面光滑与沟槽结构对其电化学氧化行为的影响。研究表明:原始形貌光滑碳纤维在电化学过程中保持形貌能力较强,相同的电化学氧化强度下,其表面氧碳比高于原始表面粗糙的碳纤维,表明其氧化程度高。X射线光电子能谱(XPS)分峰结果表明,二者表面氧含量差别来自于表面羰基含量的差异。力学性能测试结果表明具有沟槽形貌的碳纤维拉伸强度及拉伸模量提高的幅度较大,其中拉伸强度提高最大值为17.3%。将氧化前后的碳纤维制备成碳纤维增强树脂基复合材料,探讨碳纤维形貌结构对其复合材料界面性能的影响。结果表明:由具有沟槽形貌的碳纤维制备得到的复合材料层间剪切强度(ILSS)较高,表明碳纤维表面物理形貌也是影响复合材料界面的重要因素。