Determination of Water Diffusion Coefficients and Dynamics in Adhesive/Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis（EDX） is used to establish the content change of oxy- gen in the adhesive in adhesive/carbon fther reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analy-sis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of beth energy dispersive X-ray spectroscopy and elemental analysis. The de- termined results with EDX analysis are almost the same as those determined with elemental analysis and the results al- so show that the durability of the adhesive/carbon fther reinforced epoxy resin composite joints subjected to silane cou- pling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treat- ment.

Mechanical properties of short carbon/glass fiber reinforced high mechanical performance epoxy resins

To research the relationship between epoxy and fiber inherent property and mechanical properties of composite,we prepared a series of composites using three kinds of high mechanical performance epoxy resins as matrices and reinforced by the same volume fraction(5%)of short carbon and glass fiber.Their mechanical properties were investigated from the perspective of chemical structure and volume shrinkage ratio of epoxy.We analyzed their tensile strength and modulus based on the mixing rule and Halpin-Tsai equation,respectively,and studied the morphology of impact test samples by scanning electron microscope.The results show that chemical bonds formed between matrix and fiber are the most important factor to improve the mechanical properties of composite.High volume shrinkage ratio is also helpful when the fiber surface was coarse.Otherwise,the tensile strength is more sensitive to interface than the tensile modulus.It is concluded that the mechanical properties of composite are strongly affected by the chemical structure of epoxy resin,the volume shrinkage ratio of cured matrices,and properties of fiber surface.

Toughness and Fracture Mechanism of Carbon Fiber Reinforced Epoxy Composites

The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.

Microstructure of Carbon Fiber and Carbon Reinforced Plastic

This study is the investigation of the microstructure of different types of carbon fiber. They were compared with the carbonized and graphitized fibers. Results of structural researches have been presented. It was found that the damage varies from different pollution and the damage of the monofibers. The effect of the pollution of the monofiber was determined.

Fabrication and Characterization of Glass Fiber with SiC Reinforced Polymer Composites

Glass Fiber Reinforced Polymeric (GFRP) Composites are most commonly used as bumpers for vehicles, electrical equipment panels, and medical devices enclosures. These materials are also widely used for structural applications in aerospace, automotive, and in providing alternatives to traditional metallic materials. The paper fabricated epoxy and polyester resin composites by using silicon carbide in various proportions along with GFRP. The hand lay-up technique was used to fabricate the laminates. To determine the properties of fabricated composites, the tensile, impact, and flexural tests were conducted. This method of fabrication was very simple and cost-effective. Their mechanical properties like yield strength, yield strain, Young’s modulus, flexural modulus, and impact energy were investigated. The mechanical properties of the GFRP composites were also compared with the fiber volume fraction. The fiber volume fraction plays a major role in the mechanical properties of GFRP composites. Young’s modulus and tensile strength of fabricated composites were modelled and compared with measured values. The results show that composites with epoxy resin demonstrate higher strength and modulus compared to composites with polyester resin.

Progress in Recycling of Composites with Polycyanurate Matrix

Thermoset based composites are used increasingly in industry for light weight applications, mainly for aircraft, windmills and for automobiles. Fiber reinforced thermoset polymers show a number of advantages over conventional materials, like metals, especially their better performance regarding their strength-to-weight ratio. However, composite recycling is a big issue, as there are almost no established recycling methods. The authors investigate the recyclability of polycyanurate homo- and copolymers with different recycling agents under different conditions. Also the influence of the recycling process on the most important reinforcement fibers, i.e. carbon-, glass-, aramid-, and natural-fiber is investigated. The authors find that: the recycling speed is not only dependent on the temperature, but also is significantly influenced by the particular recycling agents and the polycyanurate formulation. Hence, the stability against the recycling media can be adjusted over a broad range by adjusting the polymer composition. Furthermore, the authors find that the inorganic reinforcement fibers (carbon and glass) are almost unaffected by neither recycling agent at either temperature. Aramid-fibers degrade, depending on the particular recycling agent, from slightly up to extremely strong. This leaves one with the possibility to find a combination of matrix resin and recycling agent, which does not affect the aramid-fiber significantly. In the case of natural fibers, the dependence on the particular recycling media is very strong: some media do not affect the fiber significantly;others reduce the mechanical properties (tensile strength and elongation at break) significantly, and still others even improve both mechanical properties strongly. From the Recyclate, the authors synthesize and subsequently characterize a number of new polyurethane thermosets (foamed and solid samples) with different contents of recyclate, exhibiting Tg in the range of 60°C to 128°C.

Carbon Fibers Decorated by Polyelectrolyte Complexes toward Their Epoxy Resin Composites with High Fire Safety

The achievement of both robust fire-safety and mechanical properties is of vital requirement for carbon fiber （CF） composites. To this end, a facile interracial strategy for fabricating flame-retardant carbon fibers decorated by bio-based polyelectrolyte complexes （PEC） consisting of chitosan （CH） and ammonium polyphosphate （APP） was developed, and its corresponding fire-retarded epoxy resin composites （EP/（PEC@CF）） without any other additional flame retardants were prepared. The decorated CFs were characterized by SEM- EDX, XPS and XRD, indicating that the flame-retardant PEC coating was successfully constructed on the surface of CF. Thanks to the nitrogen- and phosphorous-containing PEC, the resulting composites exhibited excellent flame retardancy as the limiting oxygen index （LOI） increased from 31.0% of EP/CF to 40.5% and UL-94 V-0 rating was achieved with only 8.1 wt% PEC. EP/（PEC8.1@CF） also performed well in cone calorimetry with the decrease of peak-heat release rate （PHRR） and smoke production rate （SPR） by 50.0% and 30.4%, respectively, and the value of fire growth rate （FIGRA） was also reduced to 3.41 kW·m-2- s-1 from 4.84 kW· m-2· s-1, suggesting a considerably enhanced fire safety. Furthermore, SEM images of the burning residues revealed that the PEC coating exhibited the dominant flame-retardant activity in condensed phase via the formation of compact phosphorus-rich char. In addition, the impact strength of the composite was improved, together with no obvious deterioration of flexural properties and glass transition temperature. Taking advantage of the features, the PEC-decorated carbon fibers and the relevant composites fabricated by the cost-effective and facile strategy would bring more chances for widespread applications.

桥梁工程中的纤维增强树脂基复合材料应用进展

为满足恶劣环境条件下现代化桥梁工程高质量建造所需材料的力学性能、耐腐蚀性及耐疲劳性等要求,基于纤维增强树脂基复合材料的优异性能,从公路桥、观赏桥、梁式桥以及超大跨度悬索桥等不同工况要求下的桥梁建设出发,总结了纤维增强树脂基复合材料的发展与应用现状。指出纤维增强树脂基复合材料在桥梁工程应用中仍存在应力损失、受风力影响大及回收处理难等弊端,并提出了主要的解决思路。

Oxidation behaviors of carbon fiber reinforced multilayer SiC–Si_(3)N_(4) matrix composites

Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.

生物基可降解环氧树脂及其可回收碳纤维复合材料的研究进展

环氧树脂是目前应用最为广泛的热固性树脂之一,其固化后会形成不溶、不熔的高度交联的三维网络结构,从而导致树脂及其碳纤维复合材料的降解困难而且难以再加工,造成了严重的资源浪费与环境污染。采用可再生生物质原料制备生物基可降解环氧树脂及其碳纤维复合材料,在缓解能源危机、减轻环境污染和实现资源再利用上具有重要意义。综述了生物基可降解环氧树脂及其可回收碳纤维复合材料的研究进展,主要包括含有热或化学不稳定键的可降解环氧树脂的合成、性能、降解机理及其碳纤维的无损回收,并总结了其优缺点。

高性能纤维增强树脂基复合材料湿热老化研究进展

高性能纤维增强树脂基复合材料具有卓越的结构整体性及抗分层等特性,在诸多工业领域中具有广泛适用性。在其储藏及使用时,制件强度会不可避免地因湿热老化造成降解和退化。探讨和揭示高性能纤维增强树脂基复合材料在不同湿热老化环境下的力学响应,对其结构件的耐久性、安全服役性能和寿命预估具有至关重要的意义。综述了国内外高性能纤维增强树脂基复合材料湿热老化方面的研究进展,介绍了其吸湿机理以及在湿热环境下的老化机理。梳理了湿热老化环境对于高性能纤维增强树脂基复合材料力学性能的影响,寿命预测模型等。最后指出了高性能纤维增强树脂基复合材料老化研究存在的问题、面临的挑战,对未来研究发展方向提出了展望。

成型温度对CF/PPEK复合材料的缺陷和力学性能影响

分别采用溶液浸渍法及真空热压成型法制备了连续碳纤维增强含杂萘联苯结构聚芳醚酮(CF/PPEK)预浸料和复合材料,对不同成型温度制备的复合材料进行了超声相控阵和三维X射线显微镜(XRM)无损检测,利用旋转流变仪、电子万能试验机、动态力学分析仪(DMA)、红外光谱仪(FT-IR)、扫描电镜(SEM)、金相显微镜对CF/PPEK复合材料进行了表征,系统研究了成型温度对纤维的浸润质量以及复合材料孔隙率、弯曲行为和层间剪切性能的影响,通过力学性能分析和断口形貌表征研究了断裂机理及缺陷对其性能产生的影响。试验结果表明:成型温度为350℃时,CF/PPEK复合材料的弯曲模量和层间剪切强度分别为125 GPa和64 MPa;成型温度为360℃时,CF/PPEK复合材料的缺陷最少,弯曲强度可达1376 MPa;而370℃高温下,复合材料出现明显缺陷,各方面性能急剧下降。

分层缺陷对CFRP层合板力学性能的影响

碳纤维增强树脂基复合材料(CFRP)具备高强度和高刚度,被广泛应用于航空航天和汽车等领域,然而碳纤维的分层缺陷会极大影响其力学性能。因此,研究分层缺陷对CFRP层合板拉伸、压缩、剪切和弯曲等力学性能的影响具有重大意义。采用复合成型工艺,将聚四氟乙烯片添加到复合材料中,经成型加工制备具有分层缺陷的CFRP层合板,考察了分层区域的尺寸和形貌,研究了分层缺陷对CFRP层合板力学性能的影响。研究发现,分层缺陷能显著降低CFRP层合板的压缩、剪切和弯曲强度,而且分层区域面积越大,CFRP层合板压缩和弯曲强度越小,但是分层区域面积的变化对拉伸强度影响较小。

连续纤维增强树脂基复合材料绿色化技术的研究进展

连续纤维增强树脂基复合材料具有轻质、高强、性能可设计等特点,是航空装备轻量化不可或缺的重要结构材料。由于其主要采用热压罐成型技术制备,成型过程能耗高,热固性树脂回收利用难、成本高,难以满足低碳绿色发展的要求,因此开展可回收绿色复合材料、复合材料低能耗制造以及回收再利用等复合材料绿色化技术研究受到了越来越广泛的重视。笔者介绍了目前连续纤维增强复合材料绿色化技术的发展现状,并探讨了连续纤维增强复合材料绿色化技术的发展前景。

基体配比对VIHPS制备GO-CF/EP复合材料微观组织与形状记忆性能的影响

碳纤维混杂增强复合材料由于具有重量轻、可设计性强等诸多优点,广泛用于汽车、海洋、航空航天等行业.根据固化剂与环氧树脂的配比化学原理,计算出石墨烯-碳纤维混杂增强树脂基(GO-CF/EP)复合材料的最佳配比为1∶5,并采用真空浸渗热压成型工艺(VIHPS)制备1∶2~1∶7共六个配比的试样,结合形状记忆性能测试及微观形貌的观察,得到固化剂与环氧树脂实际最佳配比.实验结果表明,GO-CF/EP复合材料性能主要取决于体系中交联度的大小,交联度越大,复合材料的形状记忆性能越好,微观组织形貌也较理想.当基体配比为1∶5时,GO-CF/EP复合材料体系中交联度最大,微观形貌呈现均匀致密的状态,形状固定率最大,为95.90%;形状回复率最大,为95.40%;形状回复时间最短,为80.30 s;形状回复力最大,为9.48 N.当基体配比为1∶2或1∶7时,固化剂过量或不足,交联度较小,微观组织形貌中有大量的基体聚集区,其形状记忆性能下降,形状固定率及回复率也相应减小,分别为82.99%,81.66%,81.91%,78.75%;形状回复力分别只有5.20 N和5.50 N.

碳纤维复合材料高效低碳加工综合实验设计

以碳纤维增强基复合材料(CFRP)为加工对象,设计了一种高效低碳钻削加工的综合实验项目。基于响应曲面法研究了机床主轴转速、进给速度和CFRP板材铺层顺序对CFRP构件加工质量的影响,建立了预测回归方程,最终得出最优孔口质量和最低功耗的工艺参数:最佳铺层顺序为[0°,90°,0°,90°],主轴转速在2000 r/min左右,进给速度设置在50 mm/min左右时功率最低;主轴转速在10000 r/min左右,进给速度设置在20 mm/min左右时分层因子最低。实验涉及新型材料加工、绿色加工和节能降碳等多个学科领域,能够增强学生的科研兴趣,提高实践动手能力和创新意识。

交变载荷下绝缘拉杆用GFRP电树枝劣化特性

气体绝缘组合电器(gas insulated switchgear,GIS)现场调试或运行过程多次发生绝缘拉杆内部击穿问题,影响工程投运与设备可靠性,迫切需要探明故障机理。该文选取GIS断路器绝缘拉杆用玻璃纤维增强环氧树脂复合材料(glass fiber reinforced epoxy resin composite,GFRP)为研究对象,通过计算分、合闸下绝缘拉杆主应力分布特性,设置交变载荷下电树枝劣化实验条件,研究不同交变载荷对GFRP内电树枝生长特性影响规律。结果表明,相较于单一载荷,交变载荷条件下GFRP中电树枝生长速度加快,平均击穿时间降低,击穿概率增大。基于复合材料力学仿真发现交变载荷下GFRP内树脂-纤维界面处会出现较大的应力集中,局部应力损伤已达到失效的临界值。综上,交变载荷下绝缘拉杆纤维-树脂界面机械损伤与绝缘劣化交互演进是造成绝缘击穿的主要原因,也可作为试验考核与结构设计的改进依据。

一种生物基上浆剂的制备及应用

以可再生天然生物质厚朴酚、衣康酸为原料,通过简单、高效的两步法合成生物基环氧上浆剂,并对碳纤维复合材料的耐热性能、界面性能和力学性能进行研究。实验结果表明,生物基环氧上浆剂具有良好储存稳定性和热稳定性好,碳纤维复合材料的三点弯曲和层间剪切分别提高了33.2%和36.2%。

Thermal conductivity and bending strength of SiC composites reinforced by pitch-based carbon fibers

In this work,pitch-based carbon fibers were utilized to reinforce silicon carbide(SiC)composites via reaction melting infiltration(RMI)method by controlling the reaction temperature and resin carbon content.Thermal conductivities and bending strengths of composites obtained under different preparation conditions were characterized by various analytical methods.Results showed the formation of SiC whiskers(SiC_(w))during RMI process according to vapor–solid(VS)mechanism.SiC_(w) played an important role in toughening the C_(pf)/SiC composites due to crack bridging,crack deflection,and SiC_(w) pull-out.Increase in reaction temperature during RMI process led to an initial increase in thermal conductivity along in-plane and thickness directions of composites,followed by a decline.At reaction temperature of 1600℃,thermal conductivities along the in-plane and thickness directions were estimated to be 203.00 and 39.59 W/(m×K),respectively.Under these conditions,bending strength was recorded as 186.15±3.95 MPa.Increase in resin carbon content before RMI process led to the generation of more SiC matrix.Thermal conductivities along in-plane and thickness directions remained stable with desirable values of 175.79 and 38.86 W/(m×K),respectively.By comparison,optimal bending strength improved to 244.62±3.07 MPa.In sum,these findings look promising for future application of pitch-based carbon fibers for reinforcement of SiC ceramic composites.

建筑用碳纤维增强环氧树脂复合材料的制备及其性能研究

选择以T700碳纤维为增强相,将碳纤维经浓HNO 3浸渍处理0,40,80,120和160 min后掺入到环氧树脂中,制备了碳纤维增强环氧树脂复合材料。分析了浸渍时间对复合材料微观形貌、力学性能和热稳定性的影响。结果表明,经浓HNO 3浸渍的碳纤维表面粗糙度增大,沟槽数量和深度增加,碳纤维和环氧树脂的结合强度增大;随碳纤维浸渍时间的增大,复合材料的界面剪切强度、层间剪切强度、弯曲强度和弯曲模量均先增大后减小,当浸渍时间为120 min时,复合材料的界面剪切强度和层间剪切强度均达到了最大值,分别为80.2和90.3 MPa,其弯曲强度和弯曲模量也达到了最大值,分别为902.6 MPa和79.3 GPa,且应力-应变最高点增大,弯曲性能提高;在800℃下浓HNO 3浸渍处理120 min的复合材料的残炭率最大为58.2%,热稳定性最佳。