Mechanical and thermal properties of filamentary-reinforced structural composites at cryogenic temperatures 2: Advanced composites

The low-temperature mechanical and thermal properties of advanced-fibre reinforced structural composites are reviewed. The magnitude and range of particular properties are discussed with respect to composite type and temperature. A property-material cross reference is given with a 128-entry bibliography. This is Part 2 of a two-part series Part 1 considered glass-reinforced composites.     

Greatly enhanced cryogenic mechanical properties of short carbon fiber/polyethersulfone composites by graphene oxide coating

In order to employ polyethersulfone (PES) in cryogenic engineering field, its cryogenic mechanical performance should be examined and should also be improved to meet the high requirement for cryogenic engineering application. In this work, pure PES, graphene oxide (GO)/PES, short carbon fiber (SCF)/PES, GO/SCF/PES and GO-coated SCF/PES composites are prepared using the extrusion compounding and injection molding techniques. The tensile and flexural properties of these composites are systematically investigated at a typical cryogenic temperature (77 K). It is shown that the cryogenic mechanical properties are enhanced by the addition of GO, SCFs and coated-SCFs. In particular, the GO-coated SCF/PES composites display the greatly enhanced cryogenic mechanical properties with the highest values compared to other PES composites. In addition, it is exhibited that the cryogenic mechanical properties at 77 K of PES and its composites are far higher than those at room temperature (RT).     

石墨烯-多壁碳纳米管协同增强环氧树脂复合材料的低温力学性能

为了提高环氧树脂的低温力学性能,采用石墨烯与多壁碳纳米管(MWCNTs)协同改性环氧树脂,系统研究了石墨烯-MWCNTs/环氧树脂复合材料的室温(RT)和低温(77K)力学性能。结果表明:当石墨烯的质量分数为0.1wt%,MWCNTs的质量分数为0.5wt%时,纳米填料的加入可同时改善环氧树脂的低温拉伸强度、弹性模量和冲击强度;在此最佳含量下,石墨烯-MWCNTs/环氧树脂复合材料在RT和77K时的拉伸强度皆达到最大值,比纯环氧树脂的拉伸强度分别提高了11.04%和43.78%。石墨烯和MWCNTs能协同提高环氧树脂的低温力学性能。     

三维编织复合材料热物理性能实验

针对不同编织工艺参数的三维四向编织复合材料,进行了热环境下的热物理性能实验研究,获得了热环境下三维四向编织复合材料的热物理性能变化规律及其分布特征,分析了环境温度和编织角对材料的热膨胀系数(CTE)、热传导系数(CTC)、比热(SH)以及热扩散率(TD)的影响,得到了一些重要结论。这些结果为三维编织复合材料的热物理性能数值分析以及进一步研究材料的热力耦合行为奠定了实验基础。     

超低温复合材料的研究进展

本文综述了超低温复合材料的研究背景和国内外最新进展.首先对超低温复合材料所用基体和增强材料进行了介绍,然后介绍了超低温复合材料的测试手段和主要关注的性能,主要包括结构表征、复合材料界面、力学性能、热循环使用寿命、渗漏性测试、材料损伤检测.同时,还介绍了超低温复合材料的应用.最后,本文展望了超低温复合材料的发展趋势和研究方向.     

Three-dimensional needle-punching for composites – A review

The current literature on three-dimensional (3D) needle-punched composites tends to address the aspects of preforms fabrication and composites characterization respectively. This paper aims to bring together these two aspects to provide readers with a comprehensive understanding of the subject of 3D needle-punched reinforcements for composites. Consequently, this paper contains a detailed outline of the current state of 3D needle-punched technology for manufacturing advanced composite preforms. Properties of 3D needle-punched composites and some of the predictive models available for determining these properties are also reviewed. To conclude, a number of current and potential applications of 3D needle-punched preforms for engineering composites are highlighted, and issues impeding the use of 3D needle-punched composites are also summarized.     

Improved cryogenic interlaminar shear strength of glass fabric/epoxy composites by graphene oxide

The cryogenic interlaminar shear strength (ILSS) at cryogenic temperature (77 K) of glass fabric (GF)/epoxy composites is investigated as a function of the graphene oxide (GO) weight fraction from 0.05 to 0.50 wt% relative to epoxy. For the purpose of comparison, the ILSS of the GF/epoxy composites is also examined at room temperature (RT, 298 K). The results show that the cryogenic ILSS is greatly improved by about 32.1% and the RT ILSS is enhanced by about 32.7% by the GO addition at an appropriate content of 0.3 wt% relative to epoxy. In addition, the ILSS of the composite at 77 K is much higher than that at RT due to the relatively strong interfacial GF/epoxy adhesion at 77 K compared to the RT case.     

The effect of temperature on the dynamic characteristics of heat-resistant thermoplastic composites

Two thermoplastic and two thermosetting fibrereinforced plastic composites were subjected to dynamic tests over a wide range of temperature, covering both cryogenic and hot environments. The thermal behaviour of each composite, as indicated by its dynamic mechanical properties, was assessed individually, and was compared collectively with that of the other composites.     

Effect of ultrasonication on the cryogenic tensile properties of carbon nanocoil/poly-dicyclopentadiene composites

Cryogenic tensile properties of carbon nanocoil (CNC)/poly-dicyclopentadiene (poly-DCPD) composites have been investigated experimentally. Flat tensile specimens of CNC/poly-DCPD composites with 1.0 and 1.5 vol.% CNCs were fabricated by an ultrasonic method and tested at room temperature (RT) and liquid nitrogen temperature (77 K). The effect of ultrasonication time on the cryogenic tensile properties of CNC/poly-DCPD composites was discussed. A scanning electron microscope (SEM) was also used to observe the fracture surface morphology of CNC/poly-DCPD composites. Results indicated that the tensile strength of CNC/poly-DCPD composites at RT and 77 K is affected by ultrasonication time and there is a trade-off between improving dispersion and damaging the CNC.     

Cryogenic properties of filamentary-reinforced composites: an update

Progress since 1975 in understanding the effect of cryogenic temperatures on the mechanical, elastic, thermal and electrical properties of fibre-reinforced structural composites is reviewed. The two categories considered are relatively inexpensive laminates reinforced with woven fabric or random mat and the more expensive uniaxial laminates often reinforced with high-performance, advanced fibres. The status of fundamental research and of test method development is reviewed and directions of effective future research are considered.     

造纸污泥/高密度聚乙烯复合材料的制备及性能

采用造纸污泥（PIW）填充高密度聚乙烯（HDPE）制备PIW/HDPE复合材料,并利用水浴箱、热变形维卡温度测定仪、氧指数仪、电子万能试验机、动态热机械分析仪对PIW/HDPE复合材料的吸水性能、热性能、阻燃性能、拉伸性能及动态力学性能进行分析测试。结果表明,PIW/HDPE复合材料具有良好的结合界面和拉伸性能,其最佳拉伸强度为23.18 MPa;PIW质量分数的增加会对PIW/HDPE复合材料的吸水性能、韧性产生不利的影响;但PIW质量分数的增加有利于提高PIW/HDPE复合材料的热性能、阻燃性能（其最高氧指数为29.98%）和刚性。本研究可为造纸污泥的资源化利用提供研究基础。      

聚酰亚胺纤维/双马树脂复合材料抗高速冲击性能

采用热压罐成型工艺制备聚酰亚胺纤维/双马树脂复合材料,并采用空气炮冲击实验研究聚酰亚胺纤维体积分数和环境温度对复合材料层板抗高速冲击性能的影响。结果表明:与等面重下TC4钛合金相比,S35聚酰亚胺纤维复合材料抗高速冲击性能更优,且具有优异的高温抗高冲击性能。聚酰亚胺纤维体积分数越高,复合材料层板抗高冲击性能越高,其中,73%体积分数的聚酰亚胺纤维复合材料层板室温弹道吸能可达227.0J,比等面重下TC4钛合金高240%。冲击速率较低时,复合材料弹击面出现周围含纤维分层开裂的圆形凹坑,背弹面出现沿纤维方向的分层开裂;冲击速率较高时,复合材料层板弹击面出现周围含纤维分层开裂的圆形通孔,背弹面出现沿纤维方向大面积纤维分层开裂。     

Research into mechanical properties of reaction-bonded SiC composites at cryogenic temperatures

The mechanical properties of reaction-bonded silicon carbide (RBSC) composites at cryogenic temperatures have been reported for the first time. The results show that the flexural strength and fracture toughness increase from 277.93 ± 23.21 MPa to 396.74 ± 52.74 MPa and from 3.69 ± 0.45 MPa·m^1/2 to 4.98 ± 0.53 MPa·m^1/2 as the temperature decreases from 293 K to 77 K, respectively. The XRD analysis of the phase composition reveals that there is no phase transformation in the composites at cryogenic temperatures, indicating cryogenic mechanical properties are independent of phase composition. The enhancement of mechanical properties at 77 K over room temperature could be explained by the transition of fracture mode from predominant transgranular fracture to intergranular fracture and stronger resistance to crack propagation resulting from higher residual stress at 77 K. The above results demonstrate that such composites do not undergo similar deteriorations in the fracture toughness as other materials (some kinds of metals and polymers), so it is believed that such composites could be a potential material applied in cryogenic field.     

温度对三维五向编织/环氧树脂复合材料拉伸性能的影响

研究了三维五向编织/环氧树脂复合材料和树脂基层合复合材料在室温、80℃、150℃和180℃的拉伸性能,讨论了不同温度对三维五向编织复合材料和层合复合材料拉伸的影响规律。研究结果表明,三维五向编织复合材料在80℃、150℃时的拉伸强度与室温相近,而在180℃时,比室温时的拉伸强度下降了15.37%;层合复合材料在80℃、150℃和180℃时的拉伸强度则比室温分别下降了3.45%、13.3%和34.42%。造成层合复合材料高温拉伸强度下降较大的原因是:在高温时,由于树脂被破坏,使层合复合材料发生了分层。说明相同树脂基体的复合材料,增强体结构对复合材料在高温时的拉伸性能有着重要的影响。     

Production of biopolymer composites by particle bonding

This paper describes a new technology to produce biopolymer composites at room temperature. During the process, micrometer-scale raw material is coated with zein that has strong adhesive property, which is then compressed to form a rigid material. Since this technology does not require purification of the raw materials, various types of compounds can be used as component materials. The coating of particles with zein makes use of the unique property of zein in aqueous ethanol solution. Zein molecules adsorb to the surface of hydrophilic particles when the ethanol content of solvent mixture increases. Formation of aggregates is followed to form large agglomerates. Removal of solvents from the agglomerates yields the final product. Biopolymer composites thus formed showed a broad range of compressive strengths depending on the hardness of the starting raw material used as a base component.     

Acoustic emission for monitoring the mechanical behaviour of natural fibre composites: A literature review

In recent years, natural fibres are increasingly used as reinforcements for the production of low-cost and lightweight polymer composites: other advantages include non-abrasive nature, high specific properties, and biodegradability. However, their limitations, including moisture absorption, poor wettability and large scattering in mechanical properties, and the not sufficient understanding of mechanisms controlling their mechanical behaviour and failure modes, still confine the use of natural fibre reinforced composites in non-structural applications. Acoustic emission (AE) proved useful for its capability of real-time monitoring over the whole material volume and high sensitivity to any process generating stress waves.This paper presents a literature review of AE applications in studies on natural fibre composites. The following fields of application are covered: (1) interface studies in single fibre composite (SFC) tests, (2) damage evolution and failure mechanisms detection and (3) crack propagation, including also current limitations of existing literature and future work.     

Gas permeability of various graphite/epoxy composite laminates for cryogenic storage systems

Experiments were performed to investigate the effect of cryogenic cycling on the gas permeability of various composite laminates for cryogenic storage systems. Textile composites have lower permeability than laminated composites even with increasing number of cryogenic cycles. Nano-particles dispersed in one of the ply-interfaces in tape laminates do not show improvement in permeability. Micrographs of sections of various specimens provide some insight into formation of microcracks, and damage before and after cryogenic cycling. In laminated tape composites microcracks in various layers connect and form an easy path for gas leakage. Composites wherein plies of different orientations are dispersed rather than grouped show excellent performance even after cryogenic cycling. In textile composites the damage is restricted to regions contained by the weave yarns and hence the permeability does not increase significantly with cryo-cycling.     

Multiscale fiber-reinforced thermoplastic composites incorporating carbon nanotubes: A review

This article reviews recent literature on hierarchical thermoplastic-based composites that simultaneously incorporate carbon nanotubes (CNTs) and conventional microscale fibers, and discusses the structure–property relationships of the resulting hybrids. The mixing of multiple and multiscale constituents enables the preparation of materials with new or improved properties due to synergistic effects. By exploiting the outstanding mechanical, thermal and electrical properties of CNTs, a new generation of multifunctional high-performance composites suitable for a wide variety of applications can be developed.     

Thermophysical properties of ceramic matrix composites produced by polymer pyrolysis

A unidirectional composite and a series of bidirectionally reinforced composites were fabricated using carbon fibre reinforcement in a silicon carbide matrix, which was produced by the pyrolysis of a polymer precursor. The thermal expansion over the temperature range 20–1000 °C has been measured and the thermal diffusivity measured over the temperature range 200–1200 °C. Thermal diffusivity data was converted to conductivity data using measured density and literature specific heat data. Metallographic examination has been carried out on the composites and the results are discussed in terms of the observed microstructural features.     

Micro-crack behavior of carbon fiber reinforced thermoplastic modified epoxy composites for cryogenic applications

Three different types of thermoplastics, poly(ether imide) (PEI), polycarbonate (PC), and poly(butylene terephthalate) (PBT) were used to modify epoxy for cryogenic applications. Carbon fiber reinforced thermoplastic modified epoxy composites were also prepared through vacuum-assisted resin transfer molding (RTM). Dynamic mechanical analysis (DMA) shows that the storage moduli of PEI, PC, and PBT modified epoxies are 30%, 21%, and 17% higher than that of the neat epoxy respectively. The impact strength of the modified epoxies at cryogenic temperature increases with increasing thermoplastic content up to 1.5 wt.% and then decreases for further loading (2.0 wt.%). The coefficient of thermal expansion (CTE) values of the PBT, PEI, and PC modified epoxies also decreased by 17.76%, 25.42%, and 30.15%, respectively, as compared with that of the neat epoxy. Optical microscopy image analysis suggests that the presence of PEI and PC in the carbon fiber reinforced epoxy composites can prevent the formation of micro-cracks. Therefore, both the PEI and PC were very effective in preventing micro-crack formation in the composites during thermal cycles at cryogenic condition due to their low CTE values and high impact strength.