Aluminum composites for automotive applications: A global perspective

The advancement of metal-matrix composites in the automotive market is still hampered by the low-volume usage of these materials, which is caused by their high cost in comparison with aluminum alloys and, in some cases, by the lack of theoretically predicted properties. Many significant challenges must be met as these materials reach maturity and the technology is scaled-up for automotive-component fabrication. The successful commercialization of metal-matrix composites will ultimately depend on their cost effectiveness for different applications. This requires optimum methods of processing, machining, and recycling, including some very new and advanced forming routes. For more information, contact V.M. Kevorkijan, Stampal SB d.o.o., Partizanska 38, Slovenska Bistrica 2310, Slovenia; telephone 386 62 632 567; fax 386 62 636 660; e-mail kevorkijan.varuzan@amis.net.     

颗粒增强钛基复合材料研究新进展

颗粒增强钛基复合材料具有高比强度、低密度、高弹性模量等特点，成为钛基复合材料的发展趋势。目前日本的Toyota公司采用粉末冶金技术制备了原位反应生成的TiB颗粒增强钛基复合材料，已在汽车发动机进、排气阀等部件得到应用。美国Dynamet公司开发了颗粒增强钛基复合材料CermeTi系列，利用其好的耐磨性能在军事、汽车、体育、医疗器械方面进行了开发。我国西北有色金属研究院研制出了性能优异的TP-650钛基复合材料，并且上海交通大学等亦在原位反应法方面作出了较好的结果。     

Fiber Reinforced Polyester Resins Polymerized by Microwave Source

Polyester resin based composite materials are widely used in the manufacture of fiberglass boats. Production time of fiberglass laminate components could be strongly reduced by using an intense energy source as well as microwaves. In this work a polyester resin was used with 2% by weight of catalyst and reinforced with chopped or woven glass fabric. Pure resin and composite samples were cured by microwaves exposition for different radiation times. A three point bending test was performed on all the cured samples by using an universal testing machine and the resulting fracture surfaces were observed by means of scanning electron microscopy (SEM). The results of mechanical and microscopy analyses evidenced that microwave activation lowers curing time of the composite while good mechanical properties were retained. Microwaves exposition time is crucial for mechanical performance of the composite. It was evidenced that short exposition times suffice for resin activation while long exposure times cause fast cross linking and premature matrix fracture. Furthermore high-radiation times induce bubbles growth or defects nucleation within the sample, decreasing composite performance. On the basis of such results microwave curing activation of polyester resin based composites could be proposed as a valid alternative method for faster processing of laminated materials employed for large-scale applications.     

Fiber-Reinforced CMCs: Processing,mechanical behavior,modeling

Continuous, plain-weave Nicalon-fiber reinforced SiC composites have been successfully manufactured using a novel method termed forced chemical vapor infiltration (FCVI). The FCVI technique can be modeled using the finite-volume method to optimize the processing conditions, thus saving fabrication time and cost. Theoretical modeling was conducted to evaluate the influence of fiber fabric orientation and coating thickness on the mechanical behavior of woven fabric reinforced composites. The predicted results were in good agreement with experimental data.     

Numerical and experimental analyses of woven composite reinforcement forming using a hypoelastic behaviour. Application to the double dome benchmark

Continuous textile reinforcements hold crucial role when composites are employed as load bearing components. Numerical simulations of the composite forming processes are essential in the design phase of the composite structures. The continuous approach predicts the mechanical characteristics of woven composite fabrics during forming which considers the fibrous materials as a continuum in average at macroscopic scale. An algorithm based on a hypoelastic behaviour is proposed for the simulation of composite reinforcement forming processes. It is shown here that using hypoelastic law with an objective derivative based on the warp and weft fibre rotation tensors can correctly trace the specific behaviour of the woven materials. A number of elementary tests validate the numerical output with theoretical results and the de facto standard in-plane shear test of picture frame has also been validated numerically. An experimental device for textile composite forming on a double dome has been implemented. This forming case has been defined as an international benchmark of woven composites. The simulations performed with the proposed numerical approach show a good agreement with the experimental results obtained with this double dome device.     

Simulation and experimental study on thermal deep drawing of carbon fiber woven composites

Carbon fiber woven composites are composed of carbon fiber woven and resin matrix. To reduce the manufacture cost, thermal stamping, a new forming technology, was proposed and investigated to fabricate composite part. The mechanical properties of carbon fiber have great influence on the deformation of carbon fiber composites. In this study, shear angle–displacement curves and shear load–shear angle curves were obtained from picture frame test. Thermal deep drawing experiments and simulation were conducted, and the shear load–displacement curves under different forming temperatures and shear angle–displacement curves were obtained. The results show the compression and shear between fiber bundles are the main deformation mechanism of carbon fiber woven composite. The maximum shear angle for the composites in this study is 33°. In the drawing process, the forming temperature affects the drawing force, which drops rapidly with the increasing temperature. The suitable forming temperature in deep drawing of the carbon fiber woven composite is approximately 170 °C.     

Cast aluminum-matrix composites for automotive applications

The potential automotive applications of metal-matrix composites, particularly aluminum-matrix composites, are numerous. Although some composite components have reached the demonstrator stage, there is still much work to do and many barriers to conquer before widespread application can be expected. These challenges include such issues as processing for specific properties, compiling property databases and addressing recyclability.     

CermeTi® discontinuously reinforced Ti-matrix composites: Manufacturing,properties, and applications

Advanced powder-metallurgy technology has led to the development of the CermeTi® family of titanium metalmatrix composites. Reinforcing the titanium alloy matrix with titanium carbide or titanium boride particles results in superior properties. These discontinuously reinforced titanium composites have excellent room- and elevated-temperature properties and are exceptionally wear resistant. High quality, near-net shape CermeTi composite components are being produced commercially and are being evaluated for potential applications in military vehicles, commercial automotive engines, sporting goods, industrial tooling, and biomedical devices.     

织物结构对C_f/Al复合材料微观组织与压缩性能的影响

选用ZL301合金为基体材料,采用2.5D浅交直联、三维正交和三维五向等3种结构编织了M40J碳纤维预制体,采用真空压力浸渗法制备纤维体积分数为50%的3D-C_f/Al复合材料。主要研究了织物结构对C_f/Al复合材料微观组织与压缩强度的影响。结果表明,织物结构对C_f/Al复合材料的致密度、微观组织和压缩性能影响较大。其中三维正交结构的C_f/Al复合材料的致密度和压缩强度最大,分别为99.2%和417MPa;而2.5D浅交直联结构的C_f/Al复合材料的致密度和压缩强度最小,分别为95.3%和99.8MPa。     

Metal-matrix composites in ground transportation

Metal-matrix composites (MMCs) are used in a variety of automotive and other ground transp ortation applications. This article provides a brief overview of the major applications of MMCs in ground transportation. The main attractive features of MMCs are: high strength-to-weight ratio, enhanced mechanical and thermal properties over conventional materials, improved fatigue and creep characteristics, better wear resistance, and general tailorability of properties. Because the transportation industry is extremely cost-sensitive, reducing the manufacturing costs of MMC components will aid in the use of MMCs.     

2.5维织物C_f/Al复合材料制备及其经纬向拉伸变形力学行为研究

以石墨纤维2.5维机织物为增强体,铝合金ZL301为基体材料,采用真空辅助压力浸渗法制备了2.5维织物Cf/Al复合材料,研究了3种织物预热温度下制备的复合材料相对致密度和微观组织形貌,分析了其界面产物组成与界面结构特征,测试了其经、纬向准静态拉伸变形力学行为并分析了其断口形貌。结果表明:复合材料织物的细观结构完整,内部纤维分布均匀,致密度随预热温度提高而略有上升,界面棒状产物为Al4C3相,其相对含量随预热温度的提高而增加,从而引起复合材料经向和纬向力学性能的下降。复合材料经向拉伸强度高于纬向拉伸强度,且其应力-应变行为呈现出显著的非线性特征,复合材料经向和纬向拉伸变形过程均可划分为3个阶段:初始弹性变形阶段、中间弹塑性变形阶段和最终损伤与断裂阶段。     

Cu-Al-Ni-SMA-Based High-Damping Composites

Recently, absorption of vibration energy by mechanical damping has attracted much attention in several fields such as vibration reduction in aircraft and automotive industries, nanoscale vibration isolations in high-precision electronics, building protection in civil engineering, etc. Typically, the most used high-damping materials are based on polymers due to their viscoelastic behavior. However, polymeric materials usually show a low elastic modulus and are not stable at relatively low temperatures (≈323 K). Therefore, alternative materials for damping applications are needed. In particular, shape memory alloys (SMAs), which intrinsically present high-damping capacity thanks to the dissipative hysteretic movement of interfaces under external stresses, are very good candidates for high-damping applications. A completely new approach was applied to produce high-damping composites with relatively high stiffness. Cu-Al-Ni shape memory alloy powders were embedded with metallic matrices of pure In, a In-10wt.%Sn alloy and In-Sn eutectic alloy. The production methodology is described. The composite microstructures and damping properties were characterized. A good particle distribution of the Cu-Al-Ni particles in the matrices was observed. The composites exhibit very high damping capacities in relatively wide temperature ranges. The methodology introduced provides versatility to control the temperature of maximum damping by adjusting the shape memory alloy composition.     

碳纤维编织复合材料板材热冲压成形的实验和模拟研究(英文)

提出一种新型的复合材料成形工艺,即热冲压成形,来直接成形复合材料。为了研究复合材料板的成形行为,分析了成形温度对零件的影响,进行了热弯曲和热拉深实验。实验结果表明,编织复合材料板的锁止角为30°,在成形过程中,变形载荷一般小于5 N,并且变形载荷随着温度的升高而降低。成形碳纤维复合材料板的最佳温度是170°C。采用有限元分析软件ABAQUS对模具的温度场分布和复合材料板的变形进行了数值模拟。为了研究碳纤维在成形过程中的运动,采用两节点的三维Truss单元T2D3对纤维进行网格剖分,模拟结果与试验结果相吻合。     

MANUFACTURING OF ALUMINUM/FLY ASH COMPOSITE WITH LIQUID REACTIVE SINTERING TECHNOLOGY

The Al/fly ash composites are fabricated by liquid reactive sintering P/M process with fly ash particles as intensifying phases. The reactivity and newly formed phases during liquid sintering process have been analyzed by combing Thermochemicdl data base calculation and XRD characterization. The results show that some of constituents in fly ash have reacted with liquid aluminum so that the elemental Si, Fe, Ti as well as some amount of intermetallic compounds occur. The properties of aluminum/fly ash composites have been improved. With the fraction of fly ash increase, the composite density decreases; the hardness and the modulus of the composite increases, and the composite wear resistance are significantly increased. The fly ash reinforced composites represent a sort of low cost product with possible widespread applications in the automotive, small engine, and electromechanical machinery sectors.     

Chemical assembly of silver nanoparticles on stainless steel for antimicrobial applications

Microbial adhesion on stainless steel is the most common contamination in many applications. In this work, we present a simple method to fabricate stainless steel-based antimicrobial composites by fixing silver nanoparticles onto the surface. Silver nanoparticles were covalently assembled on the surface of stainless steel by using 3-aminopropyltriethoxysilane (APTES) as the coupling agent. After 24 h immersion the release of silver ions amounts to a total of 0.07 ppm, as measured by atomic absorption spectrophotometry. The bactericidal rate of the composite on Escherichia coli (E. coli) is greater than 99%, and the inhibition zone is about 28 mm in diameter. Combining the low cost and high effectiveness in inhibiting the growth of bacteria, such composites are expected to be useful as antimicrobial materials that may have great potential antimicrobial applications.     

Additive Manufacturing of Composites and Complex Materials

Advanced composite materials form an important class of high-performance industrial materials used in weight-sensitive applications such as aerospace structures, automotive structures and sports equipment. In many of these applications, parts are made in small production runs, are highly customized and involve long process development times. Developments in additive manufacturing (AM) methods have helped in overcoming many of these limitations. The special topic of Additive Manufacturing of Composites and Complex Materials captures the state of the art in this area by collecting nine papers that present much novel advancement in this field. The studies under this topic show advancement in the area of AM of carbon fiber and graphene-reinforced composites with high thermal and electrical conductivities, development of new hollow glass particle-filled syntactic foam filaments for printing lightweight structures and integration of sensors or actuators during AM of metallic parts. Some of the studies are focused on process optimization or modification to increase the manufacturing speed or tuning manufacturing techniques to enable AM of new materials.     

形变铜基原位复合材料的研究现状与发展前景

高强度高电导率形变铜基原位复合材料是一类具有优良综合物理性能、力学性能和应用潜力的功能材料,其突出的特点是具有超高的强度和良好的电导率。结合制备Cu-15％Cr（质量分数）合金原住复合材料,阐述形变铜基原位复合材料目前的研究状况。介绍该类材料的组织演变、结构、强化导电机理和综合性能特点,同时对其制备工艺进行了介绍。指出这类材料的发展方向为高性能Cu—Cr、CU—Fe系原位复合材料的开发以及该体系材料的工业化制备和应用。     

Progress in studying the fatigue behavior of Zr-based bulk-metallic glasses and their composites

Zr-based amorphous alloys with a high glass-forming ability and thermal stability were discovered in 1990. In the following years, the alloy design increased the critical casting thickness to several centimeters, and a homogeneous dispersion of nanoscale particles was found to improve the ductility. Therefore, Zr-based bulk-metallic glasses (BMGs) are being studied widely because of their potential as structural materials. The fatigue behavior is an important characteristic of structural materials. The current review documents the fatigue studies of Zr-based BMGs and their composites. The fatigue characteristics of these alloys in different loading conditions and environments are summarized and compared in this paper. The factors affecting the fatigue behavior of the Zr-based BMGs and their composites are discussed. The mechanisms of fatigue-crack initiation and propagation in BMGs are addressed in this review. In order to broaden the scope of applications of BMGs, a fundamental understanding of the fatigue behavior is important for the design of new alloy systems and the development of the processing techniques.     

The potential applications for titanium metal powder and their life cycle impacts

It has been predicted that new processes being developed for titanium metal production as well as new fabrication techniques will see the cost of fabricated titanium fall by as much as 50%. Potential applications for lower-cost titanium powder are examined in this paper, with cookware, being identified as a possible lead product. The potential environmental benefits of using this material in place of competing materials such as stainless of competing materials such as stainless steel in chemical process equipment and automotive exhausts are also illustrated, based on a life-cycle approach.     

Bending-fatigue behavior of bulk metallic glasses and their composites

Amorphous alloys with high glass-forming ability and thermal stability were discovered in the 1990s. In the following years, the alloy design increased the critical casting thickness to several centimeters, and a homogeneous dispersion of nanoscale particles was found to improve the ductility. Therefore, bulk metallic glasses (BMGs) are being studied widely because of their potential as structural materials. The fatigue behavior is an important characteristic of structural materials. The current review documents the bending-fatigue studies of BMGs and their composites. The fatigue characteristics of these alloys in different loading conditions and environments are summarized and compared in this paper. The factors affecting the fatigue behavior of BMGs and their composites are discussed. The mechanisms of fatigue-crack initiation and propagation in BMGs are addressed in this review. In order to broaden the scope of applications of BMGs, a fundamental understanding of the fatigue behavior is critical for the design of new alloy systems and the development of the processing techniques.