碳/碳复合材料力学性能的研究进展

本文综述了碳/碳复合材料力学性能的研究进展,包括碳纤维、基体炭、界面性能、制备工艺及工艺参数等对碳/碳复合材料力学性能的影响。同时简单介绍了当今单向碳/碳复合材料力学性能的表征手段。希望对碳/碳复合材料力学性能的研究及应用提供帮助。     

Study on the mechanical properties and microstructure of high-performance carbon fiber/epoxy composites

A high-toughness epoxy has been prepared using carboxyl-terminated butadiene acrylonitrile (CTBN) as a toughening agent to modify the AG-80 epoxy resin. High-performance carbon fiber/epoxy (CF/EP) composites are fabricated using the CTBN-toughened epoxy resin as the matrix and two types of CF, namely, T800SC and T800HB, as reinforcement. The mechanical properties of the matrix, surface properties of the CFs, tensile properties, and fracture morphologies of the composites are systematically investigated to elucidate the key factors influencing interfacial bonding in high-performance CF/EP composites. The results reveal that the most significant improvement in toughness is achieved when the CTBN content is 6.90 wt.% in the epoxy resin. Owing to the high content of polar functional groups and excellent surface wettability of T800SC, the T800SC/EP composite exhibits superior mechanical properties compared with the T800HB/EP composite.     

Enhanced thermoelectric properties of carbon fiber reinforced cement composites

Thermoelectric properties of carbon fiber reinforced cement composites (CFRCs) have attracted relevant interest in recent years, due to their fascinating ability for harvesting ambient energy in urban areas and roads, and to the widespread use of cement-based materials in modern society. The enhanced effect of the thin pyrolytic carbon layer (formed at the carbon fiber/cement interface) on transport and thermoelectric properties of CFRCs has been studied. It has been demonstrated that it can enhance the electrical conduction and Seebeck coefficient of CFRCs greatly, resulting in higher power factor 2.08 µW m⁻¹ K⁻² and higher thermoelectric figure of merit 3.11×10⁻³, compared to those reported in the literature and comparable to oxide thermoelectric materials. All CFRCs with pyrolytic carbon layer, exhibit typical semiconductor behavior with activation energy of electrical conduction of 0.228-0.407 eV together with a high Seebeck coefficient. The calculation through Mott’s formula indicates the charge carrier density of CFRCs (10¹⁴–10¹⁶ cm⁻³) to be much smaller than that of typical thermoelectric materials and to increase with the carbon layer thickness. CFRCs thermal conductivity is dominated by phonon thermal conductivity, which is kept at a low level by high density of micro/nano-sized defects in the cement matrix that scatter phonons and shorten their mean free path. The appropriate carrier density and mobility induced by the amorphous structure of pyrolytic carbon is primarily responsible for the high thermoelectric figure of merit.     

Effects of Ti2SnC on the mechanical properties and tribological properties of copper/graphite composites

Copper/graphite composites and copper/graphite/Ti₂SnC composites were fabricated through the process of ball-milling, pressing and sintering. The effects of Ti₂SnC as the second lubrication component on the mechanical properties, wear resistance and lubrication properties of copper/graphite composites were studied in this paper. The results showed that copper/graphite/Ti₂SnC composites had better hardness, impact toughness, wear resistance and lubrication performance than copper/graphite composites. The optimum values of hardness, impact toughness, friction coefficient and wear rate of copper/graphite/Ti₂SnC composites were, respectively, 56 HSD, 1.8J/cm², 0.15, 9.126 × 10^?6 mm³/N·m, while these were only 45 HSD, 1.2 J/cm², 0.17, 3.534 × 10^?4 mm³/N·m of copper/graphite composites.     

In situ observation of damage nucleation in graphite and carbon/carbon composites

The flexure strength and the fracture toughness at 300 K and 77 K were measured in two isotropic polycrystalline graphites with very different microstructure and in one carbon/carbon composite. In addition, the micromechanisms of damage initiation at the notch tip were examined in situ during the fracture tests through a long focal distance microscope. It was found that the mechanical response of carbon-based materials was insensitive to the effect of cryogenic temperatures. In graphite with coarse microstructure, cracks appeared at very low stresses in various points of an ample region surrounding the notch tip, and damage progressed by their stable crack growth and link up. On the contrary, damage was localized at the notch root in graphite with a fine microstructure. High stresses were necessary to nucleate a single crack, which grew unstably, leading to immediate specimen failure. Damage in carbon/carbon composites was nucleated in the form of matrix cracks around the notch tip, but fiber yarns impeded the crack propagation until the load had increased significantly. This process was repeated several times, leading to a serrated load-deflection curve and to a marked increase in the overall fracture resistance.     

碳纤维复合材料在固体火箭上的应用

本文简要地论述了国内外碳／碳复合材料（Ｃ／Ｃ）,碳纤维增强塑料（Ｃ／Ｐ）在固体火箭发动机壳体、喷管上的应用。指出高性能,低成本碳纤维是发展我国战术固体火箭的关键。     

Mechanical properties of carbon fiber composites modified with nano-SiO2 in the interphase

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO₂ particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO₂ particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO₂ particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO₂, respectively, when the nano-SiO₂ content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO₂ containing sizing showed higher absorption energy than that of carbon fibers/epoxy composites treated by sizing agent without nano-SiO₂. Scanning electron microscopy (SEM) of impact fracture surface showed that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂-modified sizing treatment. Dynamic mechanical thermal analysis (DMTA) showed that the introduction of nano-SiO₂ to carbon fibers surface effectively improved the storage modulus of carbon fibers/epoxy.     

炭纤维增强水泥基复合材料(CFRC)的电磁性能

炭纤维增强水泥基复合材料(Carbon Fiber Reinforced Cement Composites,CFRC)是新发展起来的一种电磁屏蔽材料,它是防止电磁污染的防护性功能材料之一。本文阐述了炭纤维增强水泥基复合材料的制备成型工艺;分析了炭纤维掺入量和长度、水灰比和密实成型制备工艺、炭纤维分散性、养护龄期、外加剂、炭纤维表面化学气相沉积(CVD)处理等因素对CFRC力学性能、导电性能、压敏性能及电磁性能的影响。合适的炭纤维掺入量和长度、炭纤维的均匀分散、合理的水灰比和炭纤维表面处理是影响CFRC导电性能和电磁性能的主要因素。CFRC对电磁波的屏蔽效果除利用屏蔽效能从反射电磁波角度衡量外,亦可从吸收电磁波角度利用反射率进行评价。     

High density carbon fiber/boron nitride matrix composites: Fabrication of composites with exceptional wear resistance

This paper describes the fabrication of high density (ρ ∼ 1.75 g/cc) composites containing a hybrid (carbon and boron nitride), or complete boron nitride matrix. The composites were reinforced with either chopped or 3D needled carbon fibers. The boron nitride was introduced via liquid infiltration of a borazine oligomer that can exhibit liquid crystallinity. The processing scheme was developed for the chopped carbon fiber/boron nitride matrix composites (C/BN) and later applied to the 3D carbon fiber reinforced/boron nitride matrix composites (3D C/BN). The hybrid matrix composites were produced by infiltrating the borazine oligomer into a low density 3D needled C/C composite to yield 3D C/C-BN. In addition to achieving high densities, the processing scheme yielded d₀₀₂ spacings of 3.35 Å, which afforded boron nitride with excellent hydrolytic stability. The friction and wear properties of the composites were explored over the entire energy spectrum for aircraft braking using an inertial brake dynamometer. The C/BN composites outperformed both the previously reported C/C-BN and chopped fiber reinforced C/C. The high density 3D C/BN performed as well as both the 3D C/C and the C/BN. The 3D C/C-BN provided outstanding wear resistance, incurring nearly zero wear across the entire testing spectrum. The coefficient of friction was relatively stable with respect to energy level, varying from 0.2 to 0.3.     

Effect of fiber treatment on the mechanical properties of LDPE-henequen cellulosic fiber composites

The degree of mechanical reinforcement that could be obtained by the introduction of henequen cellulosic fibers in a low-density polyethylene, LDPE, matrix was assessed experimentally. Composite materials of LDPE-henequen cellulosic fibers were prepared by mechanical mixing. The concentration of randomly oriented fibers in the composite ranged between 0 and 30% by volume. The tensile strength of these composite materials increased up to 50% compared to that of LDPE. There is also a noticeable increase in Young's modulus for the composite materials that compares favorably with that of LDPE. As expected, the addition of the fibers decreases the ultimate strain values for the composite materials. The thermal behavior of the LDPE-henequen cellulosic fibers materials, studied by differential scanning calorimetry, DSC, showed that the presence of the fibers does not affect the thermal behavior of the LDPE matrix; thus, the interaction between fiber and matrix is probably not very intimate. Preimpregnation of the cellulosic fibers in a LDPE-xylene solution and the use of a silane coupling agent results in a small increment in the mechanical properties of the composites, which is attributed to an improvement in the interface between the fibers and the matrix. The shear properties of the composites also increased with increasing fiber content and fiber surface treatment. It was also noted that the fiber surface treatment improves fiber dispersion in the matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 197–207, 1997     

Structure and properties of UHMWPE fiber/carbon fiber hybrid composites

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m²) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006     

Experimental and numerical investigations of the interlaminar shear properties of carbon/carbon composites

Experimental tests and numerical simulations were implemented to investigate the interlaminar shear properties of carbon/carbon composites (C/Cs). A unit‐cell model, according to the microstructure of the C/Cs, was used to predict material properties of the C/Cs. A three‐dimensional finite element model was established to investigate the damage behavior of C/Cs on the basis of Linde failure criterion and damage evolution. Good agreement, in terms of the load force history and failure modes, was observed between the experimental and numerical results; this provided the applicability of the numerical simulation. The test results show that the interlaminar shear strength of the C/Cs was 10.52 MPa and the value of the simulation result was 10.89 MPa, with the relative error being less than 4%. Damage contours and stress distribution analysis of the simulation results are discussed. Fiber damage occurred at the bottom of the specimen, and matrix damage was found in the upper half of the specimen; this was similar to the appearance of the tested specimens. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44783.     

氧化石墨烯的制备及其掺杂的炭/炭复合材料导热性能研究

设定两种不同配比强酸氧化剂,以鳞片石墨为原料,采用Hummers法,制备了氧化石墨烯,再经过高温炭化得到热处理氧化石墨烯。并分别以中间相沥青为基体炭前驱体,炭纤维为增强相,氧化石墨烯及其热处理物为热疏导功能体,制备出掺杂氧化石墨烯的炭/炭复合材料。TEM、SEM等表征表明,选用强酸氧化剂组合配比用量较少的制备出的氧化石墨烯,其形貌整体上要优于用量较多的,具有独特的褶皱结构;相比于氧化石墨烯,掺杂其热处理物的复合材料界面覆盖均匀平滑且结合更优良,且其导热系数可达到60 W.m-1.K-1,是无掺杂的纯复合材料两倍多,导热系数得到了较大幅度提高。     

Effect of carbon nanofiber functionalization on the in-plane mechanical properties of carbon/epoxy multiscale composites

In this work, vapor-grown carbon nanofibers (CNFs) were functionalized using an optimized route and dispersed in the matrix of carbon fabric-reinforced epoxy composites to develop multiscale carbon/epoxy composites. Functionalization was carried out through an oxidative treatment with a mixture of HNO₃/H₂SO₄ (1 : 3) using a combination of ultrasonication and magnetic stirring. Functionalized CNFs (F-CNFs) were characterized for their morphology, length, functional groups, and degradation due to oxidative treatment. The results showed that it was possible to efficiently functionalize CNFs without any degradation through proper selection of treatment duration. F-CNFs were dispersed homogeneously into the epoxy matrix using ultrasonication in combination with high-speed mechanical stirring. The incorporation of 0.1 wt % F-CNFs led to a 65% increase in Young's modulus and a 36% in tensile strength of neat carbon/epoxy composites. The fracture surfaces were studied using scanning electron microscopy to understand the property enhancement due to F-CNFs. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhanced thermoelectric effect of carbon fiber reinforced cement composites by metallic oxide/cement interface

Thermoelectric power of carbon fiber reinforced cement composites was firstly enhanced efficiently by metallic oxide microparticles in the cement matrix. The absolute Seebeck coefficient of these composites increased steadily with increasing metallic oxide content and achieved 4–5 folds of the original one. The largest absolute thermoelectric power of +100.28 µV/°C was obtained for the composite with 5.0 wt% Bi₂O₃ microparticles. The carrier scattering of the interface between oxide microparticles and cement matrix is probably attributed to the Seebeck effect enhancement.     

Mechanical properties and ablation resistance of HfC nanowire modified carbon/carbon composites

Hafnium carbide nanowires (HfCnws) were in-situ grown in carbon/carbon (C/C) composites, and subsquently the preforms were densified by isothermal chemical vapor infiltration to obtain HfCnws modified carbon/carbon (HfCnws-C/C) composites. Morphology and microstructure of HfCnws were examined, and the effect of HfCnws on the mechanical property and ablation resistance of C/C composites were also investigated. Results show that introducing HfCnws refined the grain size of pyrolytic carbon (PyC). The out-of-plane compression, interlaminar shear and flexual strength of HfCnws-C/C composites increased by 120.80%, 45.60% and 94.65%, respectively compared with pure C/C, and the HfCnws-C/C shows good ablation resistance under oxy-acetylene flame ablation.     

Friction behaviors of carbon/carbon composites with different pyrolytic carbon textures

Friction and wear properties of carbon/carbon (C/C) composites with a smooth laminar (SL), a medium textured rough laminar (RL) and a high textured RL pyrolytic carbon texture were investigated with a home-made laboratory scale dynamometer to simulate airplane normal landing (NL), over landing (OL) and rejected take-off (RTO) conditions. The morphology of worn surfaces at different braking levels was observed with scanning electron microscopy. The results show that C/C composites with RL have nearly constant friction coefficients, stable friction curves and proper wear loss at different braking levels, while friction coefficients of C/C composites with SL pyrolytic carbon decrease intensely and their oxidation losses increase greatly under OL and RTO conditions. Therefore, C/C composites with a high and medium textured RL pyrolytic carbon may satisfy the requirements of aircraft brakes. The good friction and wear properties of C/C composites with RL are due to the properties of RL, which leads to a uniform friction film forming on the friction surface.     

Effects of needle-punched felt structure on the mechanical properties of carbon/carbon composites

The effects of needle-punched felt structure, including mass ratio of non-woven cloth to short-cut fiber web, PAN-based carbon fiber types of non-woven cloth and thickness of unit (one layer of non-woven cloth and short-cut web was named as a unit), on the flexural properties of C/C composites from pressure gradient CVI are discussed. Results show that flexural strength and modulus increase when mass ratio of non-woven cloth to short-cut fiber web changes from 7:3 to 6:4 and that PAN-based carbon fiber types of non-woven cloth strongly influence the flexural properties. The strength of C/C composites is not linear with the strength of non-woven cloth carbon fiber because of the important interface between carbon fiber and matrix carbon. It is suitable to choose T300 or T700 as reinforcing carbon fiber for C/C composites in the present study. An optimum unit number per cm of the needle-punched felts for higher flexural properties exists.     

Effect of hygrothermal conditioning on compressive strength after impact in carbon fiber/epoxy composites

Carbon fiber-reinforced polymers have been widely applied in structural parts and components in several sectors, in addition to being constantly used in environments with the presence of humidity and high temperatures, which can affect their density, hardness, and rigidity. In this work, the influence of hydrothermal conditioning on carbon fiber (CF)/epoxy composites was investigated using three types of epoxy resin and two different CF fabric reinforcements, that is, plain weave and eight harness satin (8HS) arrangements. The CF/epoxy composites were subjected to compression after impact (CAI) test by 28 and 40 J energy and then exposed to hydrothermal conditioning for 8 weeks. After the CAI tests, the visual analysis of all composites presented microbuckling mechanisms. The composites tested with 40 J energy absorbed only 2% more moisture compared with the other composites, nonimpacted, and tested with 28 J, indicating that the impact damage did not cause delamination between the layers of the composites, which could facilitate the absorption of water. All composites analyzed showed resistance to CAI even after exposure to humidity, with decreases ranging from 2.8% to 23.8% about the unconditioned specimens. The decrease in CAI also shows the influence of the type of epoxy matrix and the arrangement of the CF in fabrics.     

Fabrication of C/SiC composites by siliconizing carbon fiber reinforced nanoporous carbon matrix preforms and their properties

Reactive melt infiltration (RMI) has been proved to be one of the most promising technologies for fabrication of C/SiC composites because of its low cost and short processing cycle. However, the poor mechanical and anti-ablation properties of the RMI-C/SiC composites severely limit their practical use due to an imperfect siliconization of carbon matrixes with thick walls and micron-sized pores. Here, we report a high-performance RMI-C/SiC composite fabricated using a carbon fiber reinforced nanoporous carbon (NC) matrix preform composed of overlapping nanoparticles and abundant nanopores. For comparison, the C/C performs with conventional pyrocarbon (PyC) or resin carbon (ReC) matrixes were also used to explore the effect of carbon matrix on the composition and property of the obtained C/SiC composites. The C/SiC derived from C/NC with a high density of 2.50 g cm^?3 has dense and pure SiC matrix and intact carbon fibers due to the complete ceramization of original carbon matrix and the almost full consumption of inspersed silicon. In contrast, the counterparts based on C/PyC or C/ReC with a low density have a little SiC, much residual silicon and carbon, and many corroded fibers. As a result, the C/SiC from C/NC shows the highest flexural strength of 218.1 MPa and the lowest ablation rate of 0.168 µm s^?1 in an oxyacetylene flame of ～ 2200 °C with a duration time of 500 s. This work opens up a new way for the development of high-performance ceramic matrix composites by siliconizing the C/C preforms with nanoporous carbon matrix.