Detecting Impact Damage in Carbon Fabric/epoxy-matrix Composites by Ultrasonic F-scan and Electrical Resistance Measurement

The status and the variation of electrical resistance of impacted carbon fiber/epoxy-matrix composites were studied by ultrasonic F-scan and electrical resistance measurement The experimental results shows that impact damage energy threshold value of carbon fabric/epoxy-matrix composites can determine by using ultrasonic F-scan. When the impact energy exceeds the threshold value, damage is generated in composites. Electrical resistance of impacted composites is changed owing to the contact of each carbon fiber unit in composites, which cause a change of the series-parallel in conductors. The veracity of detecting impact damage in composites can be improved in this case.

Evaluation of Impact Damage Tolerance in Carbon Fabric/epoxy-matrix Composites by Electrical Resistance Measurement

Impact damage tolerance is provided in intensity design on composites. The compression intensity of impacted composites requires more than 60% of its original intensity. The influence of impact on compressive intensity and electrical resistance of carbon fabric/epoxy-matrix composites was studied in this paper. The experimental results shows that impact can cause damage in composites, degenerate compressive intensity, and increase resistance. The electrical resistance change rate was used as an evaluation indicator of impact damage tolerance of composites. Impact damage, which results from the applying process of composites, can be identified in time by electrical resistance measurement. So, the safety performance of composites can also be improved.

Preparation of Three-Dimensional Carbon Network Reinforced Epoxy Composites and Their Thermal Conductivity

As a thermosetting resin with excellent properties,epoxy resin is used in many areas such as electronics,transportation,aerospace,and other fields.However,its relatively low thermal conductivity limits its wide application in more demanding fields.Here,a three-dimensional carbon(3DC)network was prepared through NaCl template-assisted in situ chemical vapor deposition(CVD)and used to reinforce epoxy resin for enhancing its thermal conductivity.The 3DC was prepared with a molar ratio of sodium atom to carbon atom of 100:20,and argon atmosphere in CVD led to an optimal improvement in the thermal conductivity of epoxy resin.The thermal conductivity of epoxy resin increased by 18%when the filling content was 3 wt.%of 3DC network because of the high contact area,uniform dispersion,and enhanced formation of conductive paths with epoxy resin.As the amount of 3DC addition increases,the thermal conductivity of composites also increases.As an innovative exploration,the work presented in this paper is of great significance for the thermal conductivity application of epoxy resin in the future.

The Reinforcing Effect of Graphene on the Mechanical Properties of Carbon-Epoxy Composites

Graphene nanoplatelets (GNPs) are novel nanofillers holding attractive characteristics, including vigorous compatibility with majority polymers, outstanding mechanical, thermal, and electrical properties. In this study, the outstanding GNPs filler was reinforced to the epoxy matrix and carbon fabric/epoxy hybrid composite slabs to enrich their mechanical properties. Graphene nanoplatelets of 0.5, 1, 1.5 and 2 weight percentages were integrated into the epoxy and the physico-mechanical (microstructure, density, tensile, flexural and impact strength) properties were investigated. Furthermore, the mechanical properties of unfilled and 1 wt% GNPs filled carbon fabric/epoxy hybrid composite slabs were investigated. Subsequently, noteworthy improvement in the mechanical properties was conquered for the carbon fabric/epoxy hybrid composites.

Synthesis, Characterization and Flame-retardant Properties of Epoxy Resins and AACHH Composites

Flame retardant epoxy resins were prepared by a simple mixed method using ammonium aluminum carbonate hydroxy hydrate （AACHH） as a halogen-free flame retardant. The prepared samples were characterized by X-ray diffraction, thermogravimetric and differential scanning calorimetry, scanning electron microscope and limiting oxygen index（LOI） experiments. Effects of AACHH content on LOI of epoxy resins/AACHH composite and flame retardant mechanism were investigated and discussed. Results show that AACHH exhibites excellent flame-retardant properties in epoxy resin（EP）. When the content of AACHH was 47.4%, the LOI of EP reached 32.2%. Moreover, the initial and terminal decomposition temperature of EP increased by 48 ℃ and 40 ℃, respectively. The flame retarded mechanism of AACHH is due to the synergic flame retardant effects of diluting, cooling, decomposition resisting and obstructing.

Recyclable High-performance Carbon Fiber Reinforced Epoxy Composites Based on Dithioacetal Covalent Adaptive Network

Recycling of carbon fiber reinforced composites is important for sustainable development and the circular economy.Despite the use of dynamic chemistry,developing high-strength recyclable CFRPs remains a major challenge due to the mutual exclusivity between the dynamic and mechanical properties of materials.Here,we developed a high-strength recyclable epoxy resin(HREP)based on dynamic dithioacetal covalent adaptive network using diglycidyl ether bisphenol A(DGEBA),pentaerythritol tetra(3-mercapto-propionate)(PETMP),and vanillin epoxy resin(VEPR).At high temperatures,the exchange reaction of thermally activated dithioacetals accelerated the rearrangement of the network,giving it significant reprocessing ability.Moreover,HREP exhibited excellent solvent resistance due to the increased cross-linking density.Using this high-strength recyclable epoxy resin as the matrix and carbon fiber modified with hyperbranched ionic liquids(HBP-AMIM+PF6-)as the reinforcing agent,high performance CFRPs were successfully prepared.The tensile strength,interfacial shear strength(IFSS)and interlaminar shear strength(ILSS)of the optimized formulation(HREP20/CF-HBPPF6)were 1016.1,70.8 and 76.0 MPa,respectively.In addition,the CFRPs demonstrated excellent solvent and acid/alkali-resistance.The CFRPs could completely degrade within 24 h in DMSO at 140℃,and the recycled CF still maintained the same tensile strength and ILSS as the original after multiple degradation cycles.

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.

Improvement of thermal conductivities and simulation model for glass fabrics reinforced epoxy laminated composites via introducing hetero-structured BNN-30@BNNS fillers

Hetero-structured thermally conductive spherical boron nitride and boron nitride nanosheets(BNN-30@BNNS)fillers were prepared via electro static self-assembly method.And the corresponding thermally conductive&electrically insulating BNN-30@BNNS/Si-GFs/E-44 laminated composites were then fabricated via hot compression.BNN-30@BNNS-Ⅲ(fBNN-30/fBNNS,1/2,wt/wt)fillers presented the optimal synergistic improvement effects on the thermal conductivities of epoxy composites.When the mass fraction of BNN-30@BNNS-Ⅲwas 15 wt%,λvalue of the BNN-30@BNNS-Ⅲ/E-44 composites was up to0.61 W m^(-1)K^(-1),increased by 2.8 times compared with pure E-44(λ=0.22 W m^(-1)K^(-1)),also higher than that of the 15 wt%BNN-30/E-44(0.56 W m^(-1)K^(-1)),15 wt%BNNS/E-44(0.42 W m^(-1)K^(-1)),and 15 wt%(BNN-30/BNNS)/E-44(direct blending BNN-30/BNNS hybrid fillers,1/2,wt/wt,0.49 W m^(-1)K^(-1))composites.Theλin-plane(λ//)andλcross-plane(λ_(⊥))of 15 wt%BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites significantly reached 2.75 W m^(-1)K^(-1)and 1.32 W m^(-1)K^(-1),186.5%and 187.0%higher than those of Si-GFs/E-44 laminated composites(λ//=0.96 W m^(-1)K^(-1)andλ_(⊥)=0.46 W m^(-1)K^(-1)).Established models can well simulate heat transfer efficiency in the BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites.Under the condition of point heat source,the introduction of BNN-30@BNNS-Ⅲfillers were conducive to accelerating heat flow trans fe r.BNN-30@BNNS-Ⅲ/Si-GFs/E-44 laminated composites also demonstrated outstanding electrical insulating properties(cross-plane withstanding voltage,breakdown strength,surface&volume resistivity of 51.3 kV,23.8 kV mm^(-1),3.7×10^(14)Ω&3.4×10^(14)Ω·cm,favorable mechanical properties(flexural strength of 401.0 MPa and ILSS of 22.3 MPa),excellent dielectric properties(εof 4.92 and tanδof 0.008)and terrific thermal properties(T_(g )of 167.3℃and T_(HRI) of 199.2℃).

Durability Testing of Composite Aerospace Materials Based on a New Polymer Carbon Fiber-Reinforced Epoxy Resin

In this study,the durability of a new polymer carbonfiber-reinforced epoxy resin used to produce composite material in the aerospacefield is investigated through analysis of the corrosion phenomena occurring at the microscopic scale,and the related infrared spectra and thermal properties.It is found that light and heat can con-tribute to the aging process.In particular,the longitudinal tensile strength displays a non-monotonic trend,i.e.,itfirst increases and then decreases over time.By contrast,the longitudinal compressive and inter-laminar shear strengths do not show significant changes.It is also shown that the inter-laminar shear strength of carbonfiber/epoxy resin composites with inter-laminar hybrid structure is better than that of pure carbonfiber materials.The related resistance to corrosion can be improved by more than 41%.

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.

可控ZnO阵列改性碳织物复合材料的制备及摩擦学性能研究

碳纤维表面光滑且具有惰性,削弱了其与树脂的界面黏结,进而限制了碳织物/树脂复合材料的应用前景。基于界面工程技术,采用预埋晶种层的方式诱导ZnO微纳米阵列在碳纤维表面均匀生长,并通过改变晶种层溶度优化ZnO阵列的形貌和分布,以强化纤维/基体的界面,从而提升复合材料的力学强度和摩擦学性能。结果表明:通过对纤维表面形貌分析,晶种层浓度对ZnO微纳米阵列形貌和分布有较大的影响;当浓度为15mmol/L时,均匀且细化的ZnO阵列生长在碳纤维表面,使纤维的表面能大幅度提高,促进了树脂充分浸润,提高了力学强度;与原始复合材料相比,改性复合材料的磨损率降低了约35%,表明ZnO阵列的引入能够明显提高复合材料的耐磨性。

铁粉/碳纤维增强树脂复合材料的制备 及脆化损伤研究

将偶联剂改性纳米铁(Fe)粉与预处理后的碳纤维混合,浸润于环氧树脂基料中,经过搅拌混合制备纳米Fe粉/碳纤维增强树脂复合材料,研究了复合材料在高温老化、水浸老化环境下的脆化损伤行为。结果表明:树脂受到高温老化和水浸泡老化后会出现脆化损伤,碳纤维和纳米Fe粉加入会对该损伤有一定抑制;加入质量分数为4.0%的纳米Fe粉后,随着高温老化时间延长,碳纤维质量分数为3.0%的纳米Fe粉/碳纤维增强复合材料的拉伸强度、断裂韧性下降幅度较小,同时脆化损伤后树脂与纳米Fe粉、碳纤维仍结合紧密;碳纤维质量分数为3.0%、纳米Fe粉质量分数为4.0%的纳米Fe粉/碳纤维增强复合材料经水浸老化后,断裂韧性仍旧保持较高水平。

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。

机织角联锁变密度复合材料的面外压缩力学特性

为研究变密度结构设计对三维机织角联锁复合材料面外力学性能的影响,设计制备了三维机织角联锁不变密度复合材料、三维机织角联锁经纱变密度复合材料和三维机织角联锁纬纱变密度复合材料。结合扫描电子显微镜、数字图像相关技术和X射线计算机断层扫描等检测技术,对角联锁变密度复合材料的面外压缩力学行为、内部损伤量化和渐进损伤等进行了测试与表征。研究结果表明:上疏下密角联锁纬纱变密度复合材料展现出优异的压缩性能,其压缩比强度比不变密度复合材料高3.40%;同时,上疏下密角联锁纬纱变密度复合材料损伤体积仅为11.64 mm 3,远低于不变密度复合材料的26.90 mm 3。进一步分析得到,不变密度复合材料压缩破坏以剪切失效为主,而上疏下密角联锁纬纱变密度复合材料则为基体开裂。

Ⅳ型储氢气瓶承载层CFRP基体优选与性能研究

以SW树脂及HY4006树脂为基体树脂,以12K T700碳纤维(HY-1、HY-2、HY-3)为纤维增强体,制备Ⅳ型储氢气瓶承载层用碳纤维增强复合材料(CFRP),从固化特性、耐热性能、流变性能和树脂浇注体的力学性能等方面筛选适合的树脂基体,通过树脂对纤维的浸润性及CFRP的力学性能、微观形貌、孔隙率等筛选出最优的CFRP体系。结果表明:SW树脂的固化温度为109~142℃,固化速率快,固化时间短,黏度增长较慢,而且其浇注体力学性能好,比HY4006树脂更适合于Ⅳ型储氢气瓶的缠绕工艺;SW树脂对HY-2碳纤维的浸润性更好,起始接触角为80.06°,浸润时间仅2.5 s;由SW树脂与HY-2碳纤维制备的CFRP拉伸强度为2650 MPa,剪切强度为64.63 MPa,密度为1.67 g/cm 3,纤维体积分数为63.61%,该CFRP界面结合好,孔隙率低,力学性能优异,是Ⅳ型储氢气瓶缠绕层的理想材料。

基于VARTM的碳纤维单向与三维编织混杂织物树脂灌注工艺

为探究碳纤维单向与三维编织混杂增强环氧树脂基复合材料地铁转向架侧梁的树脂灌注成型工艺,首先基于渗透率理论模型采用非饱和径向流法分别测试得到碳纤维单向与三维编织织物的渗透率。通过数值模拟的方法对典型复合材料方形管结构进行缩比建模与网格划分,并利用PAM-RTM软件对树脂灌注成型过程进行仿真分析,预测了制备复合材料方管所需的灌注时间、灌注压力以及树脂流动过程缺陷的产生。最后根据模拟的灌注方案通过真空辅助树脂传递模塑(VARTM)成型工艺制备了碳纤维单向和三维编织混杂织物增强环氧树脂复合材料方管结构件。结果表明,通过PAM-RTM模拟VARTM工艺制备复合材料方管时树脂的流动,预测得到灌注时间为3897 s,VARTM工艺实际制备复合材料方管的灌注时间为4052 s,误差约为3.8%,在合理误差范围内。方管内部灌注压力随着与注胶口距离的增加而逐渐减小。模拟与实验的误差可能是由于实际铺层和灌注过程中树脂流动引起织物的剪切变形以及真空度的差异导致渗透性能产生变化。仿真模拟和实际制备复合材料方管均无明显缺陷产生,证明径向法织物渗透率的理论模型计算测试和仿真结果具有可靠性。

盐环境对含孔损伤碳纤维复合材料的性能影响

研究了含孔损伤T700碳纤维/环氧树脂基复合材料在不同浓度、时间和温度的盐溶液环境老化后的性能变化并分析其破坏机理。对其进行盐溶液水浸老化吸湿试验后,分析其质量变化、老化前后SEM微观形貌、玻璃化转变温度、红外光谱分析和开孔拉伸性能。结果表明,盐溶液的浓度对材料性能影响较小,而盐溶液老化的时间和温度对其影响明显,随温度和时间的增加吸湿速率越快,玻璃化转变温度下降幅度越大,试样形貌损伤破坏越严重,纤维与基体界面发生破坏,开孔拉伸强度明显下降。

双氢氧化物/官能化碳纳米管复合协效阻燃剂设计及应用

环氧树脂(EPs)广泛应用于飞机结构部件中,为其开发高性能阻燃剂对提高飞机防火安全性具有重要现实意义。本研究通过一锅法在交织的官能化碳纳米管(F-CNTs)骨架上生长镁铝双金属氢氧化物(MgAl-LDH)纳米片,构建得到二者的复合结构MgAl-LDH/F-CNTs。以MgAl-LDH/F-CNTs复合结构作为力学支撑,进一步负载CuMoO4纳米颗粒,最终得到适用于环氧树脂的MgAl-LDH/F-CNTs-CuMoO4协效阻燃剂。其中,MgAl-LDH/F-CNTs复合结构可助于实现各阻燃组分在环氧树脂聚合物基材中的均匀分散,相较于未经阻燃处理的环氧树脂材料,阻燃环氧树脂在燃烧测试中其峰值热释放速率可降低40.5%,总热释放量可降低7.49%,CO生成量和总烟气释放量可显著降低43.0%和26.3%,极限氧指数LOI提升38.2%,可见经阻燃处理后的EP复合材料阻燃性能显著提升。此外,经阻燃处理后环氧树脂拉伸、弯曲强度仅下降7.1%和22.4%,表明CNTs的添加以及MgAl-LDH/F-CNTs复合结构的构建能够有效补偿LDH添加对EP力学性能的影响。

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%。

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。