高温热处理对C/C多孔体显微结构的影响

以三维针刺碳毡作为预制体,先采用树脂单向加压浸渍结合热压固化制备了CFRP复合材料,然后通过树脂热解碳化制备出C/C多孔体。文章重点研究了高温热处理对C/C多孔体显微结构的影响。通过扫描电子显微镜观察了材料的显微结构,使用阿基米德方法测定材料的密度和气孔率,并利用压汞仪分析了材料的孔隙分布,利用X射线衍射分析碳基体的石墨化程度。结果显示,高温热处理后材料的密度降低,孔隙率增大;高温热处理没有改变材料中孔隙的类型,但使材料中三类孔隙尺寸均增大;经过高温热处理材料的石墨化度提高,部分块状碳基体转变为片层状石墨碳结构。     

连续碳纤维增强热固性酚醛树脂复合材料的3D打印工艺及性能研究

针对连续碳纤维增强热固性酚醛树脂复合材料3D打印成型工艺的技术难题,本文提出了浸渍-原位预固化-后固化的3D打印成型方案,实现了连续碳纤维增强热固性酚醛树脂复合材料的3D打印成型,并研究浸渍温度对酚醛树脂接触角与表面张力,以及打印工艺对样件形貌和力学性能的影响规律。结果表明:当浸渍温度为40 ℃,预固化温度为180 ℃时,纤维-树脂界面结合效果最佳,原料具备成型条件;当打印间距为0.5 mm时,样件的弯曲强度及模量达到最大值,分别为660.00 MPa和57.99 GPa,层间剪切强度达到20.14 MPa。此连续碳纤维增强热固性酚醛树脂复合材料一体化制备工艺解决了3D打印热固性树脂原位成型难的问题,为制备具有复杂结构的连续纤维增强热固性树脂复合材料提供了参考。     

高强高模聚乙烯纤维植物纤维纸基复合材料制备及性能

以高强高模聚乙烯（UHMWPE）短纤维和针叶木浆为原料，通过湿法成型技术结合树脂浸渍热压方法制备了UHMWPE纤维纸基复合材料，研究了原纸制备工艺和浸渍热压工艺对UHMWPE纤维纸基复合材料性能的影响。结果表明，当UHMWPE纤维与针叶木浆质量比为7∶3、针叶木浆打浆度为58°SR、酚醛树脂水溶液质量分数为10%、上胶量为44%、热压工艺为15 min、10 MPa、130℃时，制得的UHMWPE纤维纸基复合材料性能较好。当原纸经过浸渍热压后，所制备的UHMWPE纤维纸基复合材料抗张指数为59.11 N·m/g，与原纸相比抗张指数提高了6.9倍，表面变得更光滑，同时具有较低的介电常数（约1.97）、介质损耗因数（0.45×10–2）和较好的热稳定性。     

碳纤维增强树脂基复合材料孔隙率检测方法的分析比较

碳纤维增强树脂基复合材料生产过程中会产生孔隙的缺陷,孔隙会对性能造成影响,故需要对孔隙含量进行标定。以碳纤维增强双马酰亚胺树脂为研究对象,分别采用密度法、显微照相法、超声检测法、高精度X射线数字成像法等4种方法,对热压罐和微波固化成型法制备的层压板孔隙缺陷进行检测,并计算其孔隙率。研究结果表明,显微照相法、高精度X射线数字成像技术法测试的孔隙率接近,密度法的误差较大。     

非热压罐预浸料制备及成型工艺研究

采用单面胶膜浸渍的方法制备非热压罐(Out of Autoclave,以下简称"OoA")预浸料。采用三种方法测定预浸料的浸渍度,通过预浸料的细观形貌、层压板孔隙率及力学性能,系统地分析了浸渍度对碳纤维增强复合材料(CFRP)质量的影响,22%的浸渍度时性能最优。与OoA预浸料相匹配的固化工艺至关重要,通过无损检测、孔隙率、微观结构及力学性能对比分析,120℃/2 h作为第一阶段的固化工艺最适合,同时层压板热性能、力学性能与热压罐相媲美。     

固化压力对厚L形CFRP单向板纤维分布影响的实验研究

采用热压罐工艺制备了厚L形CFRP单向板,通过对其宏细观结构形貌的分析,研究压力对厚L形CFRP单向板厚度和纤维分布的影响。结果表明:采用热压罐工艺制备厚L形CFRP单向板时会出现褶皱和厚度不均匀等缺陷,预浸料层间有明显的树脂富集带。通过增加固化压力,可以降低树脂富集带的宽度,抑制厚L形CFRP单向板表面褶皱的产生,增加压实量,但会导致不同截面间纤维体积分数差异变大,外侧纤维梯度分布区变大;增加压力还会导致曲面段变薄且靠近底部纤维含量变高,靠近模具侧树脂有向平板/曲面段过渡区流动聚集的趋势。     

玄武岩纤维增强聚醚砜复合材料制备与性能

将聚醚砜树脂PES制备成水性分散液,利用水性分散液浸渍玄武岩纤维,然后通过热压成型制备了聚醚砜为基体的连续玄武岩纤维增强复合材料,研究了不同树脂含量下复合材料的热学和力学性能。结果表明,以聚醚砜和连续玄武岩纤维质量比为5∶5时得到的复合材料综合性能最优,该复合材料的初始分解温度为522℃,较纯PES树脂高15℃;弯曲强度为546 MPa,弯曲模量可达51.3 GPa。     

中温固化环氧树脂芳纶Ⅲ纤维复合材料性能研究

对芳纶Ⅲ纤维和及其织物(F-3S175)的性能进行测试,采用热熔法制备了3233中温固化环氧树脂F-3S175芳纶布预浸料,通过热压罐法成型复合材料层合板和蜂窝夹层板,进行性能测试,与Kevlar 49纤维进行对比。结果表明,芳纶Ⅲ纤维、织物和其3233树脂复合材料性能高于Kevlar 49芳纶纤维、织物及其复合材料性能。     

先进树脂基复合材料高压微波固化工艺实验研究

先进树脂基复合材料在航空航天领域应用广泛,采用高效率、低能耗的微波固化工艺以获得令人满意的固化质量的构件,已逐渐引起学者们的关注。将高压引入树脂基复合材料的固化过程中,通过缺陷分析、显微金相、力学性能检测等手段,对先进树脂基复合材料的高压微波固化质量进行实验研究。结果表明,高压微波固化能有效实现树脂基复合材料的固化,与传统热压罐工艺相比,高压微波固化工艺可获得低孔隙、少缺陷、纤维/树脂界面结合较好的固化质量,拉伸强度提高4.82%,层间剪切强度提高10.32%。研究结果为复合材料高压微波固化技术的推广与应用提供了实验数据支撑。     

一种OOA成型中温固化环氧树脂芳纶纤维预浸料研究

研制一种OOA(非热压罐)成型中温固化环氧树脂芳纶纤维预浸料,对树脂进行流变性能和DSC分析,确定树脂的固化工艺。采用热熔法制备OOA成型芳纶纤维预浸料,通过真空袋法成型复合材料层压板,进行性能测试。结果表明,OOA成型中温固化环氧树脂芳纶纤维预浸料适合真空袋法成型复合材料,层压板孔隙率低,力学性能满足要求,复合材料玻璃化转变温度高,具有较好的耐热性。     

Two-Dimensional-Woven-Carbon-Fiber-Reinforced Silicon Carbide/Carbon Matrix Composites Produced by Reaction Bonding

Plane-woven-fabric carbon-fiber-reinforced SiC/C matrix composites were fabricated at 1450°C via reaction bonding and impregnation with phenolic resin. The relationship between the flexural strength and the open porosity of the composites is dependent on the heat-treatment temperature before the impregnation. The flexural strength of composites heat-treated at 1000°C (open porosity of ∼15%) was ∼300 MPa, whereas that of composites heat-treated at 1450°C (open porosity of ∼12%) was only ∼240 MPa. The heat-treatment temperatures before the impregnation step might control the interface properties between the fiber and the matrix.     

大型整体毡炭/炭复合材料的密度分布及影响

研究了采用化学气相沉积(CVD)和树脂浸溃／固化／碳化相结合的致密工艺制备的大型整体毡炭／炭复合材料的密度、开孔率及压缩强度的分布状况，分析了致密化工艺中存在的可能造成这种分布现象的因素并讨论了密度分布可能带来的影响。     

Improved interlaminar shear properties of multiscale carbon fiber composites with bucky paper interleaves made from carbon nanofibers

The effects of bucky paper interleaves made from carbon nanofibers on interlaminar shear properties of carbon fiber reinforced composites (CFRPs) are studied. The study includes fabrication of bucky papers, resin impregnation by different techniques, i.e., soaking, hot-compression and vacuum filtration, followed by β-stage curing and the integration with carbon fiber prepregs to produce CFRP composites with bucky paper interleaves. The vacuum infiltration technique results in the best quality of polymer impregnation through bucky papers. Remarkable 31% and 104% improvements in interlaminar shear strength and mode-II shear interlaminar fracture toughness of the multiscale composites, respectively, are achieved with the incorporation of interleaves at failure-prone locations. The pertinent mechanisms responsible for the ameliorating effects of interleaves include improved interfacial adhesion and matrix shear strength for the interlaminar strengthening and crack-tip bridging and meandering for the toughening. The present technique can be used to incorporate carbon nanotubes (CNTs) or carbon nanofibers (CNFs) of high contents to strengthen/toughen at selective locations in FRP composites, which has not been possible previously because of the high viscosity caused by randomly-oriented CNTs/CNFs in a polymer resin.     

Low-cost preparation and frictional behaviour of a three-dimensional needled carbon/silicon carbide composite

A low-cost carbon/silicon carbide (C/SiC) composite was manufactured by phenolic resin impregnation–pyrolysis combined with liquid silicon infiltration. The carbon fiber preform was prepared by three-dimensional needling. A carbon/carbon composite with a density of 1.22 g/cm³ after only one impregnation–pyrolysis cycle was achieved by using hot-pressing curing. The density of the final C/SiC was 2.10 g/cm³ with a porosity of 4.50% and SiC-content of 45.73%. The C/SiC composite had a high thermal conductivity of 48.72 W/(m K) perpendicular to the friction surface and demonstrated good friction and wear properties. The static and average dynamic friction coefficients were 0.68 and 0.32 (at a braking velocity of 28 m/s). The weight wear rates of the rotating disk and stationary disk were respectively 7.71 and 5.60 mg/cycle with linear wear rates, 1.67 and 1.22 μm/cycle, at a braking velocity of 28 m/s.     

Solid freeform fabrication of soybean oil-based composites reinforced with clay and fibers

Soybean oil/epoxy-based composites were prepared by an extrusion freeform fabrication method. These composites were reinforced with a combination of organically modified clay and fibers. The intercalated behavior of the epoxy resin in the presence of organo-modified clay was investigated by X-ray diffraction and transmission electron microscopy. The mixture of epoxidized soybean oil and EPON^® 828 resin was modified with a gelling agent to solidify the materials until curing occurred. The flexural modulus reached 4.86 GPa with glass fiber reinforcement at 50.6 wt% loading. It was shown that the fiber orientation followed the direction of motion of the writing head that deposited the resins and had an influence on the properties of the composite. The composites cured by curing agent jeffamine EDR-148 were found to have lower mechanical properties than those cured with triethylenetetramine, diethylenetriamine, and polyethylenimine. In addition, the effects of clay loading and fiber loading on mechanical properties of the composites were studied and reported.     

Effect of compaction treatment on laminated CFRP composites fabricated by vacuum‐assisted resin‐transfer molding

Carbon fiber‐reinforced polymer (CFRP) composites were fabricated using ordinary and compaction setups (OS and CS, respectively) in the vacuum‐assisted resin‐transfer molding (VARTM) process. The mechanical properties and acoustic emission (AE) spectra of the CFRP composites were compared among fabricated samples. The CFRP plates with sequences of [+30/−30]₆ were sectioned to make specimens for Mode I interlaminar fracture tests and three‐point bending tests. The difference between the material properties and AE characteristics of the OS and CS specimens were statistically compared using one‐way analysis of variance. The OS specimens had a thicker resin layer, a higher resin fraction, larger average fracture toughness, and AE energy corresponding to the Mode I fracture, whereas the CS specimens had more macro‐scale voids and higher bending strength. AE analysis showed that frequency bands in the interlaminar fracture tests corresponding to matrix‐related fracture were dominant for the OS specimens, whereas those corresponding to the mixed fracture mode of the fiber and matrix fracture were dominant for the CS specimens. In the bending tests, mixed fiber‐matrix fractures were dominant for the OS specimens, and fiber‐related fractures were dominant for the CS specimens. In conclusion, the compaction treatment diminished interlaminar fracture toughness, due to the enhanced formation of macro‐scale voids around the fiber bundles during the resin impregnation stage. However, the bending strength improved with an increased fiber volume fraction. POLYM. COMPOS., 38:217–226, 2017. © 2015 Society of Plastics Engineers     

Improving the interlaminar shear strength and thermal conductivity of carbon fiber/epoxy laminates by utilizing the graphene-coated carbon fiber

The poor interlaminar properties restrict the application of carbon fiber reinforced polymer (CFRP) composites. In this work, a novel method for fabricating a graded interface structure is developed to improve the through-thickness thermal conductivity of CFRP composites. High-strength graphene nano-plates (GnP) and phenolic resin (PF) were selected to deposit on the surface of carbon fiber to design a novel CF/Epoxy laminates, where a simultaneous improvement of interlaminar shear strength (ILSS) and through-thickness thermal conductivity was observed. With addition of 1 wt % of GnP-PF in CF, 37.04% increase of the ILSS, and 16.67% enhancement of thermal conductivity compared to the original CFRP. The mechanism for improvement of both ILSS and thermal conductivity was studied by scanning electron microscopy and nano-indentation, where a better interface formed by GnP-PF has been clearly observed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47061.     

Reactive melt infiltrated Cf/SiC composites with robust matrix derived from novel engineered pyrolytic carbon structure

Needle-punched C_f/SiC composites were fabricated by a novel pore tuned reactive melt infiltration (RMI) process. The novel hierarchically porous carbon structure in the fiber preform with the porosity well open to liquid silicon was engineered by impregnation of phenolic resin with addition of a pore former. Neither residual bulk carbon nor residual bulk silicon is detected in the matrix of the C_f/SiC composites prepared by the pore tuned RMI, indicating that a robust matrix with homogenous SiC can be formed. The composite prepared by the pore tuned RMI exhibits a tensile strength of 159±5 MPa, which is 46% higher than that without addition of pore former.     

热塑性树脂浸渍黄麻纤维毡的研究

研究了热塑性树脂PP(聚丙烯)浸渍黄麻纤维毡的速率及相关因素,以解决天然纤维毡增强热塑性复合材料中连续熔融浸渍,考察了浸渍速率、温度等参数对其加工成型及力学性能的影响.用改装的毛细管流变仪作为实验装置,以一维Darcy定律处理实验数据,研究了压力对毡体空隙率以及熔体粘度对浸渍速率的影响.结果显示,相同的压力下,浸渍速率和熔体粘度成反比,麻纤维毡的压缩空隙率都要高于玻璃纤维毡.通过对纤维毡体结构、可压缩性、纤维直径以及毡体渗透率进行对比,进一步讨论了纤维毡浸渍速率的影响因素.表明麻纤维平均直径远大于玻璃纤维,纤维堆叠产生的空隙明显大于玻璃纤维且在麻纤维毡中不存在玻璃纤维毡中的束内浸渍,麻毡的浸渍速率约为玻纤毡的3.5倍,平均渗透率K约为玻纤毡的14倍.运用毛细管模型计算了两种毡体的Kozeny常数,其值分别为2950和442.