Toughness Effect of Graphene Oxide-Nano Silica on Thermal-Mechanical Performance of Epoxy Resin

A graphene oxide/nano-silica(GOS)hybrid was rapidly and easily synthesized using graphene oxide(GO)and nano-silica(nano-SiO_(2))as raw materials,and the synthesized GOS was used to improve the mechanical properties of epoxy resin(EP).The modified EP with different mass fractions of GOS(0,0.1%,0.2%,0.3%and 0.4%)were prepared and studied.The structure,thermal stability,mechanical properties,fracture toughness and failure morphology of the modified EP were analyzed.The results showed that the tensile strength of GOS modified EP increased from 40.6 MPa to 80.2 MPa compared with EP,the critical stress intensity factor of GOS modified EP increased by 65.9%from 0.82 MPa·m^(1/2)to 1.36 MPa·m^(1/2),indicating a significant enhancement in fracture toughness.In addition,failure morphology was observed by scanning electron microscopy(SEM)observation.The toughness mechanism of the modified EP was also discussed.Finally,the thermal stability of the modified EP was improved by the addition of GOS.Compared with neat EP,the initial thermal degradation temperature and glass transition temperature of GOS modified EP increased by 4.5℃and 10.3℃,respectively.

Mechanical properties and fracture toughness of rail steels and thermite welds at low temperature

Brittle fracture occurs frequently in rails and thermite welded joints, which intimidates the security and reliability of railway ser- vice. Railways in cold regions, such as Qinghai-Tibet Railway, make the problem of brittle fi＇acture in rails even worse. A series of tests such as uniaxial tensile tests, Charpy impact tests, and three-point bending tests were carried out at low temperature to investigate the mechanical properties and fracture toughness of U71Mn and U75V rail steels and their thermite welds. Fracture micromechanisms were analyzed by scanning electron microscopy （SEM） on the fracture surfaces of the tested specimens. The ductility indices （percentage elongation aider frac- ture and percentage reduction of area） and the toughness indices （Charpy impact energy Ak and plane-strain fracture toughness Kic） of the two kinds of rail steels and the corresponding thermite welds all decrease as the temperature decreases. The thermite welds are more critical to fracture than the rail steel base metals, as indicated by a higher yield-to-ultimate ratio and a much lower Charpy impact energy. U71Mn rail steel is relatively higher in toughness than U75V, as demonstrated by larger Ak and Klc values. Therefore, U71Mn rail steel and the corresponding thermite weld are recommended in railway construction and maintenance in cold regions.

Effect of graphene oxide on the corrosion,mechanical and biological properties of Mg-based nanocomposite

This study investigates the effect of graphene oxide(GO)on the mechanical and corrosion behavior,antibacterial performance,and cell response of Mg–Zn–Mn(MZM)nanocomposite.MZM/GO nanocomposites with different amounts of GO(i.e.,0.5 wt%,1.0 wt%,and1.5 wt%)were fabricated by the semi-powder metallurgy method.The influence of GO on the MZM nanocomposite was analyzed through the hardness,compressive,corrosion,antibacterial,and cytotoxicity tests.The experimental results showed that,with the increase in the amount of GO(0.5 wt%and 1.5 wt%),the hardness value,compressive strength,and antibacterial performance of the MZM nanocomposite increased,whereas the cell viability and osteogenesis level decreased after the addition of 1.5 wt%GO.Moreover,the electrochemical examination results showed that the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation in 0.5 wt%GO.In summary,MZM nanocomposites reinforced with GO can be used for implant applications because of their antibacterial performance and mechanical property.

Effect of Fillers on Mechanical Properties and Fracture Toughness of Glass Fabric Reinforced Epoxy Composites

Plain weave woven glass fabric reinforced epoxy (G-E) composite filled with two different types of fillers namely graphite, silicon carbide (each 5 and 10 wt%) was fabricated by hand lay-up method and compressed using hot press. These composites were investigated for their static mechanical properties such as tensile, flexural properties and impact strength as well as mode-I fracture toughness as per ASTM standards. Experimental results on mechanical properties indicate that the strength and the modulus in tensile and flexural mode for G-E composite increase with increasing filler loading. The unfilled G-E composite has the tensile strength of 305 MPa and increased to 404.2 MPa for 10 wt% silicon carbide. However, in three-point bend mode, addition of graphite in G-E showed the highest flexural strength as well as modulus. Mode-I fracture toughness test results indicated that the graphite filler loading improved the toughness of G-E composite. Selected failed samples under tensile, bending and mode-I fracture were examined using scanning electron microscope to identify the fracture features.

Mechanical Properties of Ni-Coated Single Graphene Sheet and Their Embedded Aluminum Matrix Composites

The effects of Ni coating on the mechanical behaviors of single graphene sheet and their embedded Al matrix composites under axial tension are investigated using molecular dynamics （MD） simulation method. The results show that the Young＇s moduli and tensile strength of graphene obviously decrease after Ni coating. The results also show that the mechanical properties of Al matrix can be obviously increased by embedding a single graphene sheet. From the simulation, we also find that the Young＇s modulus and tensile strength of the Ni-coated graphene/Al composite is obviously larger than those of the uncoated graphene/Al composite. The increased magnitude of the Young＇s modulus and tensile strength of graphene/Al composite are 52.27% and 32.32% at 0.01 K, respectively, due to Ni coating. By exploring the effects of temperature on the mechanical properties of single graphene sheet and their embedded Al matrix composites, it is found that the higher temperature leads to the lower critical strain and tensile strength.

Effect of sintering temperature on pore ratio and mechanical properties of composite structure in nano graphene reinforced ZA27 based composites

Nano graphene platelet(Gr)reinforced nano composites with a zinc–aluminum alloy(ZA27)matrix were produced by powder metallurgy at four different mass ratios(0.5wt%,1.0wt%,2.0wt%and 4.0wt%)and three different sintering temperatures(425,450,and 475°C).In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure,the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope.Hardness,transverse rupture,and abrasion wear tests were performed to determine the mechanical properties.According to the test results,the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased.However,when the composites produced in different reinforcement ratios were evaluated,the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.

Review of research on the mechanical properties of the human tooth

‘Bronze teeth＇ reflect the mechanical properties of natural teeth to a certain extent. Their mechanical properties resemble those of a tough metal, and the gradient of these properties lies in the direction from outside to inside. These attributes confer human teeth with effective mastication ability. Understanding the various mechanical properties of human teeth and dental materials is the basis for the development of restorative materials. In this study, the elastic properties, dynamic mechanical properties （visco-elasticity） and fracture mechanical properties of enamel and dentin were reviewed to provide a more thorough understanding of the mechanical properties of human teeth.

Effect of Micro-scale Y Addition on the Fracture Properties of Al–Cu–Mn Alloy

Rare earth(RE) elements have positive e ects on Al alloy, while most research is focused on microstructure and mechanical properties. As important application indices, toughness and plasticity are properties that are sensitive to alloy fracture characteristics, and few research studies have characterized the fracture properties of Al–Cu–Mn alloy on RE elements. The e ect of di erent contents of Y on the fracture properties of Al–Cu–Mn alloy is investigated. T6 heat treatment(solid solution and artificial aging treatment), optical microscope(OM), scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS) methods are applied to the alloy. Results showed that when Y ele?ment is present at 0.1%, the section of the as?cast alloy has smaller sized dimples and the fracture mode presents duc?tile features. Slight changes in hardness are also observed and maintained at about 60 HV. With increasing content of the RE element Y from 0.1 to 0.5%, the θ phase and Cu atoms in the matrix were reduced and most stopped at Grain boundaries(GBs). Micro?segregation and an enriched zone of Y near the GBs gradually increased. At the same time, the inter?metallic compound AlCuY is aggregated at grain junctions causing deterioration of the micro?structure and fracture properties of the alloy. After T6 treatment, the flatness of the fracture surface was lower than that of all the as?cast alloy showing lots of dimples and teared edges with a significant increase in hardness. When Y content was 0.1%, the strength and hardness of the alloy increased due to refinement of the grain strengthening e ect. The content of Y elements segregated in the inter?dendritic zone and GBs is reduced. Plasticity and deformation compatibility also improved, making cracks di cult to form and merge with each other along adjacent grain junctions and providing an increased potential for ductile fracture. This paper proposes the addition of RE Y as an e ective and prospective strategy to improve the fracture properties of the Al–Cu–Mn alloy and provide a meaningful reference in terms of improving overall performance.

Carbon nanotube and graphene reinforced magnesium matrix composites:A state-of-the-art review

Magnesium(Mg)composites reinforced with carbon-based nanomaterial(CBN)often exhibit low density,enhanced strength,good conductivity,improved wear resistance,and excellent biocompatibility when compared to current industry Mg alloys.This review aims to critically evaluate recent developments in Mg-CBN composites and is divided into five sections:First,a brief introduction to Mg-CBN composites is provided,followed by a discussion of different fabrication techniques for these composites,including powder metallurgy,casting,friction stir processing,and selective laser melting.A particular focus is on the current processing challenges,including dispersion strategies to create homogeneous Mg-CBN composites.The effect of processing on the quantifying disorder in CBNs and distinguishing different sp2carbon materials is also highlighted.Then,the effect of CBN on various properties of Mg-CBN composites is thoroughly analyzed,and the strengthening efficiency of CNTs and graphene in the Mg matrix is examined.Finally,the potential applications of Mg-CBN composites in various industries are proposed,followed by a summary and suggestions for future research directions in the field of Mg-CBN composites.

Microstructure and mechanical properties of twostep Cu-alloyed ADI treated by different second step austempering temperatures and times

Austempering ductile iron (ADI) is an attractive material due to its excellent comprehensive mechanical properties. However, the deficit in elongation and toughness always threatens its security application. Two-step austempering process is an effective way to improve elongation and toughness simultaneously. In the present work, the influence of the amount, morphology and distribution of ferrite and austenite on mechanical properties of ADI under different second-step austempering parameters has been analyzed. Results show that the amount of austenite and its carbon content decrease with increasing of second-step temperature. Carbide begins to precipitate as second-step austempering temperature reaches 380 °C. These factors together influence the mechanical properties of two-step Cu-alloyed ADI. Impact energy and fracture toughness are strongly affected by second-step austempering temperature, and are dramatically decreased with increase of second-step austempering temperature. Elongation remains constant when the second-step temperature is below 360 °C, and then it is rapidly decreased with further increase of second-step temperature. Strength is slightly influenced by second-step temperature. Ferrite morphology is not influenced by second-step austempering duration, while blocky retained austenite size is slightly decreased with the increasing of second-step austempering time. The amount of retained austenite is decreased while the carbon content of retained austenite is increased with the extending of second-step austempering time. The substructure of austenite is transformed from dislocation to twin when second-step austempering time exceeds 60 min. Strength and elongation are improved slightly with extending of second-step time. Impact energy and fracture toughness initially decrease with the extending of second-step time, and then remain constant when the time is longer than 60 min. This is a result of austenite content decreasing and carbon content of austenite increasing. The second-step austempering time mainly influences austenite content and its carbon content, which is a result of carbon diffusion behavior variation.

Influence of Macro-Topography on Damage Tolerance and Fracture Toughness of Monolithic Epoxy for Tribological Applications

Influence of topographical features on mechanical properties of monolithic epoxy samples has been studied. The topographical features studied include waviness (Wa), roughness average (Ra), root mean square value (Rq), and maximum roughness height (Rmax or Rz). The Rz of as-cast monolithic epoxy samples was 13.93 μm. By treating with velvet cloth, the Rz value significantly decreased to 2.28 μm. The Rz value of monolithic epoxy sample treated with abrasive paper 1200P was 4.85 μm which was also lower than that of as-cast monolithic epoxy samples. However, Rz values significantly increased by treating with abrasive papers 320P and 60P and became 20.32 μm and 39.32 μm, respectively. It was interesting to note that although Ra, Wa, and Rq, all increased by treating the monolithic epoxy samples with abrasive paper 1200P, however, Rz decreased by abrasive paper 1200P. A weight loss of up to 17% was observed in monolithic epoxy samples after the treatment with the abrasive papers. Both V-shaped and U-shaped notches were produced on the surfaces of the samples. The mechanical properties were significantly degraded due to surface notches mainly because of the associated stress concentration effect. The topographical features also influenced the dynamic mechanical properties and fracture mode.

Fractography Analysis with Topographical Features of Multi-Layer Graphene Reinforced Epoxy Nanocomposites

The stiff and fragile structure of thermosetting polymers, such as epoxy, accomplices the innate cracks to cause fracture and therefore the applications of monolithic epoxy are not ubiquitous. However, it is well established that when reinforced especially by nano-fillers, its ability to withstand crack propagation is propitiously improved. The crack is either deflected or bifurcated when interacting with strong nano-filler such as Multi-Layer Graphene (MLG). Due to the deflection and bifurcation of cracks, specific fracture patterns are observed. Although these fracture patterns seem aesthetically appealing, however, if delved deeper, they can further be used to estimate the influence of nano-filler on the mechanical properties. Here we show that, by a meticulous examination of topographical features of fractured patterns, various important aspects related to fillers can be approximated such as dispersion state, interfacial interactions, presence of agglomerates, and overall influence of the incorporation of filler on the mechanical properties of nanocomposites.

轧制方向对新型125KSI高钢级油套管性能的影响

利用室温拉伸试验、冲击试验、断裂韧性试验检验了超深井用新型125KSI高钢级油套管中沿扎向和垂直于扎向的强度、塑性、冲击韧性和断裂韧性。通过OM、SEM和EDS技术,对显微组织、晶粒长宽比和夹杂物分布进行了分析,讨论了显微组织对油套管各种性能的影响。结果表明,油套管材的微观组织由板条状回火马氏体和均匀弥散分布的细小Al_(2)O_(3)-MnS类混合夹杂物组成,晶粒为8.5级。轧制后,沿管道轧制方向的晶粒长宽比增加,导致强度增加,塑性降低且平行于管道轧向的冲击韧性下降;沿管道轧制方向的夹杂物分布更加集中,导致临界距离变小,裂纹扩展方向垂直于轧制方向的断裂韧性降低。

煤体微观力学特性的纳米压痕实验研究

煤体力学性质的测定与研究对煤炭高效开采和灾害预防具有重要的理论价值。煤较为松软破碎,强度较低,难以制备标准的力学测试煤样,也无法回收利用从而进行重复测试。亟需探索新的力学测试方法完善煤的力学特性研究。纳米压痕技术可以测定小尺度煤体微观力学特性,具有样品易制作、实验快速、样品无损的特点。结合矿物组分测试、形貌扫描和纳米压痕实验,研究了4种煤的物性特征及微观力学性质。结果表明,实验煤样矿物类别主要包括非晶态有机质和黏土、石英和碳酸盐类矿物,不同煤的矿物组分有显著差异。煤的3D形貌图显示不同煤表面粗糙度差异明显,煤中矿物分布具有显著非均质性。纳米压痕实验结果表明:①煤样中石英和碳酸盐类矿物质量分数越高,会导致煤样表面力学性质越强,压痕深度越小;②煤样表面的组分越复杂,煤的非均质性越明显,表面微观力学性质分布的离散程度越高;③煤的煤阶越高,变质程度越高,外部孔隙越发育,导致断裂韧度提高;④对压痕试验结果进行拟合,发现弹性模量与坚固性系数、弹性模量与断裂韧度均具有明显的线性关系,并且弹性模量与断裂韧度的线性关系受峰值载荷的影响。

修复材料与牙体组织力学适配性的研究进展

牙齿作为发挥咀嚼功能的主要器官,可承受无数次功能性接触,这与它的力学性能和组织结构密切相关。牙釉质和牙本质的硬度较高,并且它们具有梯度化的结构,这使得牙齿既能承受咬合力,又不致轻易折裂。当牙体组织缺损时,往往需要全冠修复体来恢复牙齿正常的形态与功能。常用的全冠修复材料有金属材料、陶瓷材料以及最近兴起的聚醚醚酮材料。金属材料在美学方面存在一定劣势,目前在临床上应用相对较少。不同组成成分的陶瓷材料在性能及美学上的表现有所差异,但弹性模量与硬度过高,在力学性能方面都超过了牙体组织,与牙体组织学力学性能不匹配。与此不同,聚醚醚酮材料的弹性模量低于牙体组织,与骨组织相似,但通过纤维增强等方式能够提高它的性能。当修复材料与牙体组织的力学性能并不完全适配时,两者之间的界面往往形成潜在的薄弱环节,最终影响修复的稳定性和长期效果。本文介绍了牙釉质和牙本质的力学性能以及相对应的结构特点,并在此基础上,分析现有修复材料的优势与局限性,进一步探究口腔全冠仿生设计的可能性。

(Cr,La)_(2)(C,N)添加对Ti(C,N)基金属陶瓷结构与性能的影响

在开放体系下采用高温碳管炉制备了(Cr,La)_(2)(C,N)粉末,并将其作为添加剂制备Ti(C,N)基金属陶瓷。利用X射线衍射仪、扫描电镜、万能力学试验机及维氏硬度计等设备研究了(Cr,La)_(2)(C,N)添加对Ti(C,N)基金属陶瓷微观组织和力学性能的影响。结果表明,(Cr,La)_(2)(C,N)的添加能够有效细化Ti(C,N)基金属陶瓷的硬质相晶粒,其中Cr、La元素主要固溶于粘结相,La元素促进了硬质相的溶解–析出过程,金属陶瓷的抗弯强度、硬度以及断裂韧性等力学性能得到明显改善。当添加(Cr,La)_(2)(C,N)的质量分数为5.0%时,Ti(C,N)基金属陶瓷的综合力学性能达到最佳,抗弯强度为2002 MPa,维氏硬度为1643 MPa,断裂韧性为11.22 MPa·m^(1/2)。

陶瓷材料断裂韧性的高效评价方法的探究

近几年新兴陶瓷产业不断拓展,如芯片用高导热陶瓷基板等,推动着材料性能测试技术走向批量化和高效化。断裂韧性是陶瓷材料的一个重要力学性能指标,但现有测试技术存在测试结果误差较大、制样过程繁琐、效率低等问题,使其在工业研发设计及生产中受到一定程度的限制。笔者综述了材料韧性的相关测试技术及对应测试指标包括断裂韧性、断裂能、J积分、冲击韧性等,对比分析了常见陶瓷材料的断裂韧性及其相关力学性能指标,以寻求一种高效的准确的评价方法;考量了陶瓷材料的抗弯强度的适用依据和适用范围,并通过相关文献数据验证其准确性。而笔者将为批量化工业研发设计和陶瓷材料生产过程中的韧性评价提供新的思路。

微型双螺杆挤出技术制备二维纳米片复合材料

为了研究不同2D纳米片对聚碳酸酯力学性能的影响,利用熔融共混法通过微型双螺杆挤出机制备了不同含量的石墨烯/聚碳酸酯复合材料和氮化硼/聚碳酸酯复合材料。通过注塑机注塑出试样,并对不同含量的两种2D纳米片/聚碳酸酯复合材料的力学性能进行了对比分析。结果表明,两种2D纳米片都对聚碳酸酯的力学性能有少量提升效果。其中,添加量为5%的氮化硼/聚碳酸酯复合材料拉伸强度达到(75.85±1.11)MPa,比纯聚碳酸酯材料提升了16.9%。随着2D纳米片的继续添加,拉伸强度开始下降,但弹性模量持续上升。

TiAlSiN纳米复合涂层的研究进展

随着现代加工需求的不断提高,对刀具涂层的性能要求愈发苛刻。相较于CrN、TiN、TiAlN等传统硬质涂层,TiAlSiN纳米复合涂层凭借优异的硬度、耐磨性、耐蚀性和高温抗氧化性,成为了减少工件磨损、延长使用寿命的最佳候选材料,被广泛应用于汽车、航空航天、通用机械等刀具加工领域,引起了研究者的广泛关注。为此,本文综述了TiAlSiN纳米复合涂层在微观结构、力学性能和实际应用方面的研究进展;阐述了TiAlSiN纳米复合涂层元素组成、制备工艺对其微观结构的影响规律及作用机理;重点讨论了TiAlSiN纳米复合涂层力学性能(如硬度、韧性、结合力及耐磨性)的影响规律及作用机制,包括归纳了Hall-Petch效应、固溶强化、共格外延、模量差异、晶界复合在内的5种TiAlSiN纳米复合涂层的增硬机理,对比分析了不同涂层增韧的途径与机制,探讨了TiAlSiN纳米复合涂层结合力与摩擦学性能的影响因素;最后,介绍了TiAlSiN纳米复合涂层在刀具、模具等典型应用领域的发展现状,并对TiAlSiN纳米复合涂层未来的研究趋势和发展方向进行了展望,以期为发展高效、高性能、低成本的刀具硬质涂层提供参考。

石墨烯纳米复合材料的制备及性能研究

在材料科学领域,石墨烯作为一种具有革命性特性的纳米材料,在提高传统材料力学强度、电导性和热稳定性方面开辟全新可能性,吸引广泛的研究兴趣。鉴于此,该文旨在探究石墨烯纳米复合材料的制备方法及其性能特征,以期为其在工业和科技领域的应用提供理论基础和实践指导。在材料与设备方面,该文选择适合石墨烯复合材料制备的原材料和先进设备。通过设计的实验步骤,成功制备出石墨烯纳米复合材料,并采用多种表征手段对所得复合材料的结构和性能进行详细分析。在性能分析方面,该研究重点关注石墨烯纳米复合材料的力学性能、导电性能和热稳定性。研究结果表明,加入石墨烯显著改善复合材料的力学强度和导电性能。