动态压缩下一种碳纤维织物增强复合材料的各向异性力学性能实验研究

为获得一种碳纤维二维正交平纹机织布增强树脂基复合材料准静态和动态压缩力学性能, 对其三个主方向(垂直于碳布方向、碳布经向、碳布纬向) , 分别利用Inst ron 试验机和SHPB 实验技术, 进行了准静态压缩和动态压缩实验。得到了三个主方向从低应变率(10 -3 / s) 到高应变率(约103 / s) 下的压缩应力2应变曲线和压缩强度, 并通过分析得到了三个主方向上的动态压缩响应特点: 垂直于碳布方向的力学性能及其与应变率的相关性主要由树脂基体所控制; 碳布经向和纬向的力学性能主要由碳纤维所控制, 并且和纤维初始微屈曲相关。最后, 分别给出三个主方向上的压缩强度和弹性模量与应变率相关性的表达式。      

基于RTM技术的碳纤维/聚酰亚胺复合材料舵面一体化制备与验证

设计了一种碳纤维/聚酰亚胺复合材料舵面结构,采用PAM-RTM软件模拟了舵面在注胶过程中的树脂流动,根据模拟结果设计了成型模具,并通过树脂传递模塑(RTM)工艺制备了耐高温碳纤维/聚酰亚胺复合材料舵面,对其进行了力学试验,并将三维有限元分析结果与试验结果对比。试验结果表明,碳纤维/聚酰亚胺复合材料舵面在150%的使用载荷下保持了结构的完整性,骨架的最大应变为2 408×10–6,复合材料蒙皮的最大应变为2 371×10–6。有限元分析结果表明,金属骨架的最大应力出现在舵轴根部圆弧过渡区,而碳纤维/聚酰亚胺复合材料蒙皮的最大应力出现在与垫片外圆弧接触处;碳纤维/聚酰亚胺复合材料舵面的初始破坏为蒙皮单向带横向拉伸失效。      

碳纤维/玻璃纤维混织布及其环氧复合材料

碳纤维和玻璃纤维混合增强树脂基复合材料目前都用单丝铺放工艺。为了改善单向预浸料的工艺性能,开发了碳纤维和玻璃纤维混织布。用它们制备复合材料,操作方便,可用手糊或模压工艺。根据设计需要,可调整混织布的经纬比例和布的构造,以获最佳性能/价格比。本文通过六种混织布/环氧复合材料的力学性能测定和估算,表明其拉伸和弯曲的强度和弹性模量符合“混合律”。在碳纤维占总纤维的体积分量为26%时出现最低的复合材料强度,而碳纤维的体积分量超过53%时才对复合材料的强度和弹性模量部有提高。      

碳纤维毡/环氧树脂复合材料的力阻效应

以短切碳纤维毡和环氧树脂为原材料制成复合材料,考察了该材料在单向拉伸载荷下的力阻响应。实验结果表明,该材料具有正力阻效应(拉应变引起材料的电阻增大)。其中,单层碳纤维毡/环氧树脂复合材料的力阻灵敏度可达13.9,但在加载过程中其电阻表现出逐渐衰减趋势;多层碳纤维毡/环氧树脂复合材料的力阻性能更为稳定,但随着层数的增加灵敏度逐渐降低,5层复合材料的力阻灵敏度下降到5.7。多层复合材料的立体导电网络是其稳定性提升和灵敏度下降的主要原因。将碳纤维毡/环氧树脂多层复合材料敷设在梁结构表面形成智能表层,利用其力阻性能实现了梁结构在循环载荷下的变形监测以及在单调载荷作用下损伤监测。     

碳纤维/聚醚醚酮单向带各向异性导电行为的尺度效应

具有导电各向异性的高分子复合材料(ACPCs)在场发射装置及传感器设计领域具有重要应用。常规的ACPCs很难获得超大导电各向异性系数,且力学性能有限。本文采用碳纤维(CF)宽展、表面浸润与树脂复合一体化超薄热塑性单向带制备方法,制备厚度为0.04 mm和0.1 mm的CF增强聚醚醚酮(CF/PEEK)复合材料单向带,以PEEK纤维为纬线制备CF/PEEK复合材料单向编织布,采用热成型工艺制备CF/PEEK复合材料单向层合板。利用数字万用表和霍尔效应系统测试层合板面内及厚度方向的电阻率和面内的电子迁移率;采用超景深显微镜观察CF/PEEK复合材料单向层合板面内和厚度方向的纤维排列形貌。结果表明,超薄CF/PEEK复合材料单向层合板面内(纤维方向与横向)导电率之比高达377,而面内横向和厚度方向的导电率之比接近1,表明CF/PEEK复合材料获得了良好的横观各向同性;超薄化CF/PEEK复合材料的面内电子迁移行为同样具有巨大的各向异性,这一结果为CF/PEEK复合材料在场发射器件、传感器设计及其灵敏度调控方面提供了实验基础。      

炭黑/碳纤维/ABS电磁屏蔽复合材料的制备及其性能研究

采用硅烷偶联剂KH550改性炭黑(CB),浓硝酸氧化碳纤维(CF),将表面处理前后的炭黑和碳纤维与丙烯腈-丁二烯-苯乙烯(ABS)树脂通过混炼挤出制备了电磁屏蔽复合材料,考察了炭黑、碳纤维含量及表面处理对复合材料体积电阻率和屏蔽效能的影响。实验结果表明,采用KH550改性炭黑可以达到改性目的,浓硝酸氧化碳纤维后,其表面接上了羰基和羧基。随着炭黑含量增加,复合材料的体积电阻率逐渐下降,且变化规律符合"渗滤效应",在100～1800MHz频率范围内,屏蔽效能逐渐增加,采用1%KH550改性炭黑后,导电性能和屏蔽效能均得到提高。加入碳纤维后,复合材料的导电性能和屏蔽效能均有较大提高,且含量为2%时,分别达到最大值,采用浓硝酸氧化碳纤维后,导电性能得到进一步提高,屏蔽效能提高了1dB左右。     

用镀Cu-Fe碳纤维制备的铜基复合材料

用连续电镀法在碳纤维表面上先镀铜后镀铁,制备了镀Cu—Fe双镀层的碳纤维,研究了碳纤维与Cu—Fe双镀层的高温相容性,并用镀Cu—Fe的碳纤维制备了单向、混向铜基复合材料。测试了复合材料的弯曲强度、线热膨胀系数和电阻率。     

短碳纤维增强聚乳酸的制备与性能研究

采用熔融挤出法制备了短碳纤维/聚乳酸复合材料,通过力学性能测试、SEM和固体流变分析等方法研究了短碳纤维含量对复合材料力学性能、体积电阻率和硬度的影响。结果表明:在实验范围内,随着短碳纤维含量的增加,复合材料的力学性能提高,体积电阻率显著下降,而其洛氏硬度变化不大。     

镀镍碳纤维-碳纤维-玻璃纤维/乙烯基酯树脂导电复合材料的设计制备及其电磁性能

本研究旨在设计制备兼具电和磁功能的新型导电复合材料。采用具有良好导电性的短切碳纤维（CF）与兼具磁性和导电性的短切镀镍碳纤维（Ni-CF）作为功能体,以短切玻璃纤维（GF）作为填料,以乙烯基酯树脂（VER）作为基体,设计制备电磁性能可调控的导电复合材料。分别研究了CF含量对CF-GF/VER导电复合材料体积电阻率的影响、Ni-CF长度对（Ni-CF）-CF-GF/VER导电复合材料体积电阻率的影响,重点研究了Ni-CF含量对（Ni-CF）-CF-GF/VER导电复合材料体积电阻率和磁导率的影响,并初步探索了导电复合材料的电磁屏蔽性能。结果表明：（Ni-CF）-CF-GF/VER导电复合材料体积电阻率在0.35~36.48 Ω·cm范围内可调,磁导率在0.2~0.7内可调。CF和Ni-CF的含量和长度都会对（Ni-CF）-CF-GF/VER导电复合材料电磁性能产生较大影响。制备的（Ni-CF）-CF-GF/VER导电复合材料有望应用于电磁屏蔽领域。     

汽车前地板真空导入树脂体系的研究

本文研究了一种适用于汽车前地板真空导入成型工艺的树脂体系;具体研究了该树脂浇注体的力学和热学性能;并对该树脂体系与T700、12K东丽单向碳纤维布制备的复合材料板进行了力学测试和金相显微观察;最后对该树脂体系的真空导入过程进行了模拟和试验。     

不同预制体结构炭/炭复合材料烧蚀性能

采用电弧驻点烧蚀实验方法, 测试了分别以细编穿刺毡和针刺无纬布整体毡为增强体的2种C/C复合材料的烧蚀率, 并用电子扫描显微镜观察了烧蚀表面形貌。结果表明: C/C复合材料的烧蚀由化学烧蚀和机械剥蚀共同控制, 以机械剥蚀为主; 细编穿刺毡结构C/C复合材料由于Z向纤维束的存在, 加速了材料烧蚀表面粗糙度的变化, 烧蚀率略高于针刺无纬布整体毡结构C/C复合材料; 针刺无纬布整体毡结构C/C复合材料中无纬布层与烧蚀气流垂直, 具有良好的烧蚀性能。      

基于纤维束/环氧树脂复合材料试验的单向层合板横向拉伸强度预测方法

实验研究表明,纤维束/环氧树脂复合材料试件的横向拉伸强度与工程上常用的单向层合板横向拉伸强度在趋势上具有很好的相关性,但是数值上存在一定差距。本文使用两种碳纤维和两种环氧树脂制备了三种纤维束/环氧树脂复合材料和单向层合板,并分别测量了纤维束/环氧树脂复合材料和单向层合板的横向拉伸强度,以及环氧基体的拉伸强度。在实验基础上,应用Griffith断裂强度理论建立了纤维束/环氧树脂复合材料和单向层合板的横向拉伸强度的关系模型,通过两种复合材料实验的结果拟合了该模型中的参数。利用第三种复合材料实验进行校验,发现该模型预测的单向层合板横向拉伸强度与实测强度之间达到很好的一致性,相对偏差为9%。采用本文提出的方法,可以用较为简单的纤维束/环氧树脂复合材料和环氧基体拉伸试验预测单向层合板的横向拉伸强度。     

Evaluation of time-dependent change in fiber stress profiles during long-term pull-out tests at constant loads using Raman spectroscopy

Constant-load pull-out tests were carried out on single-fiber model composite specimens for 500 to 1,000 hours in order to investigate the time-dependent change in fiber axial stress profiles resulting from matrix creep in unidirectional continuous fiber-reinforced composites. Three resins used as the matrix materials, in which single carbon fibers were embedded, were normal epoxy, a blend with a more flexible epoxy, and UV-curable acrylic. The time-dependent change in fiber stress profiles in the constant-load pull-out tests was measured using Raman spectroscopy, and creep and relaxation tests for the matrix resins themselves were performed. It was observed that the normal epoxy matrix composite exhibited only a negligible change in the fiber stress profile with time whereas the flexible epoxy and UV-curable acrylic matrices allowed, respectively, considerable and significant changes. These observations were shown to be consistent with the creep and stress relaxation test results of the matrix resins. It was also found that the time-dependent change in fiber stress was much slower in the experiment than in the prediction based on perfect bonding at the fiber/matrix interface. The interfacial slip that occurred in the composites tested could be responsible for the gradual variation in fiber stress profiles.     

碳纤维(碳毡)/树脂复合吸波材料的研究

分别研究了平铺排布的碳毡和单向排布的碳纤维类吸波复合材料的微波吸收特性。结果表明:单向排布的聚丙烯腈基碳纤维的吸波性能与纤维的排布间距和纤维含量密切相关。本实验条件下可获得有效带宽大于3 GHz,10 dB以下的反射衰减。平铺排布碳毡的吸波性能随碳毡含量的影响较大,含量0.27 wt%时,在8 GHz~18 GHz 频段获得90 %以上的吸收率。     

An evaluation of the elastic properties and thermal expansion coefficients of medium and high modulus graphite fibers

In this work, the elastic properties and coefficients of thermal expansion of T650-35, M40J and M60J graphite fibers were determined from the macroscopic properties of either unidirectional and/or woven composites of these fibers embedded in polyimide resins. The T650-35 fibers were embedded in a PMR-15 matrix, whereas the M40J and M60J fibers were embedded in a PMR-II-50 polyimide. The three-component oscillator resonance method was employed to determine the elastic properties of the unidirectional and woven composites and their neat resins. The macroscopic coefficients of thermal expansion of the composites and the neat resins were measured by length dilatometry. Subsequently, the fiber properties were calculated from the unidirectional composite macro-data using the Eshelby/Mori-Tanaka approach. For the woven composites, a finite element approach based on the concept of a representative volume element was employed to determine the elastic and thermal properties of the fibers. In the case of the T650-35 fibers, both the longitudinal and transverse elastic and thermal properties of the fibers determined from the unidirectional and woven composites agreed very well with each other. However, for the M40J fibers, noticeable differences were observed between the fiber properties determined from the unidirectional and woven system, which was attributed to the lack of transverse isotropy of the unidirectional system. Since the properties of the M60J fibers were evaluated only from the woven system no direct comparison could be made between the properties obtained from the unidirectional and woven composite architectures. Overall, the methodology was shown to be highly applicable for the accurate determination of fiber properties from both unidirectional and woven systems.     

单向连续碳纤维-玻璃纤维层间混杂增强环氧树脂基复合材料的力学性能

为了研究连续单向纤维的层间混杂方式对复合材料力学性能及破坏方式的影响,采用碳纤维-玻璃纤维体积比为1∶1,以拉-挤成型法制备了具有不同层间混杂结构的连续单向纤维增强环氧树脂基复合材料,并研究了不同层间混杂结构的连续单向碳纤维-玻璃纤维增强环氧树脂基复合材料的力学性能及破坏形式。结果表明：具有层间混杂结构的复合材料抗拉强度处于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料之间,复合材料的拉伸断裂方式为劈裂;具有层间混杂结构的复合材料的层间剪切强度均优于纯碳纤维/环氧树脂复合材料和纯玻璃纤维/环氧树脂复合材料,复合材料的剪切断裂方式为层间断裂。     

炭纤维增强明胶复合材料的性能研究

制备了不同形式炭纤维增强的明胶复合材料,对不同复合材料的力学性能进行了测量与分析,并对复合材料的拉伸断口进行了观察,研究表明,长炭纤维增强明胶（CL/Gel)复合材料具有最高的拉伸强度,剪切强度和模量,而炭纤维毡增强明胶（CF/Gel)复合材料因内部存在较多的孔隙使其力学性能最差,因此,炭纤维毡不能用于增强明胶材料,由于纺织炭纤维布增强明胶（Cw/Gel)复合材料的纤维维束内亦有孔隙,炭纤维布的增强效果不及长炭纤维。     

Compressive response and failure of fiber reinforced unidirectional composites

The compressive response of polymer matrix fiber reinforced unidirectional composites (PMC's) is investigated via a combination of experiment and analysis. The study accounts for the nonlinear constitutive response of the polymer matrix material and examines the effect of fiber geometric imperfections, fiber mechanical properties and fiber volume fraction on the measured compressive strength and compressive failure mechanism.Glass and carbon fiber reinforced unidirectional composite specimens are manufactured in-house with fiber volume fractions ranging over 1060 percent. Compression test results with these specimens show that carbon fiber composites have lower compressive strengths than glass fiber composites. Glass fiber composites demonstrate a splitting failure mode for a range of low fiber volume fractions and a simultaneous splitting/kink banding failure mode for high fiber volume fractions. Carbon fiber composites show kink banding throughout the range of fiber volume fractions examined. Nonlinear material properties of the matrix, orthotropic material properties of the carbon fiber, initial geometric fiber imperfections and nonuniform fiber volume fraction are all included in an appropriate finite element analysis to explain some of the observed experimental results. A new analytical model predictionof the splitting failure mode shows that this failure mode is favorable for glass fiber composites, which is in agreement with test results. Furthermore, this modelis able to show the influence of fiber mechanical properties, fiber volume fraction and fiber geometry on the splitting failure mode.     

整体毡纤维体积含量对CVD增密的影响

将三组不同纤维体积含量的整体毡采用等温CVD进行沉积热解炭增密,结合CVD沉积过程中整体毡内气体传质数学模型,研究了整体毡的纤维体积含量对CVD增密过程的影响。结果表明纤维体积含量低的整体毡沉积时增重率高;纤维体积含量高的整体毡容易获得较高密度的C/C复合材料;纤维体积含量超过35％的整体毡经过300h的化学气相沉积,坯体的体积密度能达到1．52g／cm^3。     

Bending reinforcement of timber beams with composite carbon fiber and basalt fiber materials

This work shows a study based on data obtained experimentally using bending tests of pine timber beams reinforced with composite materials. Fibers used for the execution of the reinforcement are basalt and carbon. Basalt fiber composites are applied in different grammages, whereas with carbon composites, unidirectional and bidirectional fabrics are used. The behavior of the beams was analyzed regarding the reinforcement variables applied, and the results are compared with those of the tested beams without reinforcement. This work proves the good behavior of fiber reinforce plastic (FRP) with basalt fiber when applied to timber beams, and that of bidirectional carbon fabrics as opposed to the unidirectional ones.