Wf／ZrTiCuNiBe非晶合金复合材料的界面特征与性能

用渗流铸造水淬法制备了φ6mm×50mm的W纤维增强的Zr4125Ti13．75Cu12.5Ni10Be22.5非晶合金复合材料。采用扫描电镜（SEM）分析了相同渗流时间，不同渗流温度复合材料的界面反应形貌，并采用Push-out法测定了界面剪切强度，讨论了界面特征、界面剪切强度与宏观压缩断裂行为之间的关系。结果表明：渗流铸造法制备的W纤维增强Zr41.25Ti13．75Cu12.5Ni10Be22.5非晶合金复合材料明显提高了非晶合金的塑性和断裂强度。复合材料界面结合包括界面扩散和界面反应两个过程。界面反应程度加剧时界面剪切强度增大，复合材料的破坏方式由纵向劈裂转变为剪切破坏。     

Deformation behavior and crack propagation on interface of Al/Cu laminated composites in uniaxial tensile test

The microstructural characterization and uniaxial tensile tests of Al/Cu laminated composites were taken to investigate the interface effect and fracture process of the composites.The electron microscopic graphs before and after tensile test were used to evaluate the fracture behavior.Experimental results show that the fracture surfaces of laminated composites mainly present brittle failure characteristics,accompanied with several dimples on the matrixes and a few tearing on the interface.Cracks generally initiate from the interfacial interlayer and variously propagate depending on the interfacial bonding.It is found that Cu/Al interface with enhanced bonding strength generally hinders the propagation of interlayer cracks,while the interface with weak bonding delaminates by the cracks propagation through the interfacial defects.The additional shear stress on the interface between Cu and Al layers due to their different tensile ductilities aggravates the interfacial propagation of cracks.The local plastic deformation of individual matrix layer then occurs after cracks coalesce and failure in the interface.Therefore,the strong bonding interface and matching properties between individual matrix layers are required to improve the fracture performance of Al/Cu laminated composites.     

界面反应对SiC纤维增强钛基复合材料界面剪切强度的影响

利用考虑界面反应层的有限元模型,分析了界面反应对复合材料界面剪切强度的影响.有限元预测得出,界面剪切强度随着界面反应增强而增大.并且,建立了界面反应层厚度和界面剪切强度的关系式.     

Study of Interfacial Stress Distribution in SiC Fiber Reinforced Titanium Matrix Composites on Transverse Tensile Tests

A combination of the transverse tensile test and the unilaterally coupled finite element method was used to evaluate the interfacial normal bond strength and stress distribution of titanium matrix composites (TMCs). In addition, in order to identify the interface shear failure mode of TMCs under transverse loading, both the push-out test and the finite element method have been developed to characterize the interfacial shear strength of TMCs, which is the interfacial shear failure criterion. This article studies the results of the experiments, which suggested that the interfacial normal bond and shear strength of SiC_f/Ti-6Al-4V were 300 and 350 MPa, respectively, and the interface failure mode of TMCs under the transverse tensile test was radial failure rather than shear failure. Moreover, the effect of residual stress on the radial stress is also discussed in detail in this article.     

钨丝增强铜基复合材料的动态力学性能及断裂特性

通过渗流铸造的方法制备出Wf/Cu82Al10Fe4Ni4复合材料,采用分离式霍普金森压杆(SHPB)和扫描电镜(SEM)研究其动态压缩行为及断裂特性。结果表明:复合材料界面结合紧密,受冲击时体现出良好的界面结合强度;在应变率为2000s-1下动态压缩材料发生部分塑性变形,局部表面出现裂纹;在应变率为3000s-1下动态压缩材料的动态压缩强度达到2500MPa,材料内部出现钨丝劈裂、钨丝弯曲断裂以及基体合金断裂3种破坏模式。同时,在材料的断裂面上出现大量熔化带,分析认为熔化是随着应变率的提高而出现的,它改变了复合材料的断裂方式,加速了Wf/Cu82Al10Fe4Ni4复合材料的整体失效。     

Microstructures and compressive properties of AZ91D/fly-ash cenospheres composites

Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4.     

TiAlN涂层的热残余应力分析

采用有限元方法分析氮铝钛涂层的残余热应力,研究不同的基体及过渡层对残余热应力分布的影响。结果表明：当基体为硬质合金时,涂层内以拉应力为主,而基体为不锈钢时,涂层内以压应力为主;增加过渡层可以使涂层内的残余应力减少40%以上;硬质合金基体中涂层的拉应力随基体钴含量和涂层厚度的增加而减少;无过渡层时,不锈钢基体存在明显的塑性约束区,有过渡层时,随着界面应力的减少,塑性约束区明显减小或消失。因此,通过不同的涂层和基体搭配可以改善应力场,同时增加过渡层可以缓和界面应力和增强界面结合力。     

The analysis of Armos fibers reinforced poly(phthalazinone ether sulfone ketone) composite surfaces after oxygen plasma treatment

The effects of oxygen plasma treatment on both the fiber surface and interfacial adhesion of Armos fiber reinforced PPESK composites were investigated in this paper. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to analyze fiber surface chemical composition and surface roughness, respectively. The results indicated that oxygen plasma treatment had introduced a large amount of reactive functional groups onto the fiber surface and the fiber surface roughness was increased largely. The interlaminar shear strength (ILSS) of the untreated and oxygen plasma-treated composites was measured to evaluate the interfacial adhesion. The values of ILSS were enhanced dramatically; the water molecule diffusion into composite along interface was prevented effectively. The composite fracture mode was observed by scanning electron microscopy (SEM), which showed that the primary failure mode varied from interface failure to matrix failure after oxygen plasma treatment. Results indicated that oxygen plasma treatment was an effective method to improve the interfacial adhesion properties of Armos fiber reinforced PPESK composites by both chemical bonding and physical effects.     

The mechanisms of interfacial failure for lateral force-sensing microindentation test: finite element analysis

The interfacial bond strength for coatings and composites can be quantitatively determined using a newly developed lateral force-sensing microindentation method. In this study, a finite element analysis was made to investigate the interfacial failure mechanisms for Cu–ceramic and Al alloy–ceramic interfaces. The model is validated by comparing obtained results of the finite element analysis with analytical solutions. Two different interfacial failure mechanisms, depending on material properties and microindentation positions, are proposed. As demonstrated, interfacial debonding may result from shear stress or a coupling of tensile stress and shear stress at the interface, corresponding to material “pile-up” deformation or “sink-in” deformation. In addition, the high sensitivity of the lateral force response to interfacial debonding, associated with two different interfacial failure mechanisms, is also examined.     

中等加载速率下微波损伤砂岩的动态抗压强度及破坏机理（英文）

为了研究微波加热对岩石动态特性和破坏机制的影响,使用改进的分离式霍普金森压杆系统对微波辐射砂岩试样进行动态压缩试验。结果表明,微波辐射能有效降低砂岩的抗压强度。冲击荷载作用下试样呈现出3种不同的破坏模式：拉伸破坏、拉伸-剪切复合破坏和压缩-剪切破坏。利用实测的纵、横波速度计算得到的动态泊松比来描述砂岩的变形特征。随着微波功率和加热时间的增加,泊松比先下降后略有增加,转折点温度出现在244.6°C。此外,微观结构特征表明,微波辐射对岩石产生脱水、扩孔和致裂效应。基于岩石内部热应力和蒸汽压力,探讨微波辐射对岩石的损伤机理,为实验结果提供合理的解释。     

A model for predicting micromechanical interfacial adhesion in polymer composites

The mechanical behavior of fiber-reinforced composites is largely determined by adhesion at the fiber-matrix interface. Thus, a fundamental understanding of the interfacial region and a quantitative characterization of the level of interfacial adhesion can contribute to an evaluation of the mechanical behavior and performance of composite materials. Among numerous techniques for interface characterization, the vibration damping method has attracted continually more attention because it provides sensitive and nondestructive detection of the interfacial region in composites. In the research presented here, a new optical system for measuring vibration damping was introduced, and a model for evaluating the interfacial adhesion between fiber and matrix from a damping parameter was developed. A quantitative relationship between the dynamic (vibration damping) and static (interfacial shear strength) adhesion measurements was established. The experimental data from glass-fiber-reinforced epoxy resin composites with different interfacial treatments showed good agreement with the theoretical model.     

Finite Element Analysis of Push-Out Test of SiC Fiber Reinforced Titanium Matrix Composites

Based on the interphase layer model and the spring layer model, an improved interface model was developed to evaluate the interfacial shear strength of Titanium matrix composites(TMCs) and to analyze the effects of various parameters on the interfacial properties. The results showed that the improved interface model is more suitable for calculating the interfacial properties of SiC fiber reinforced titanium matrix composites. The interfacial shear strength of SiC/Timetal-834 predicted is 500 MPa. In additio...     

氧化铝基复合陶瓷-金属钎焊界面的热应力

用Ag-Cu-Ti钎料钎焊SiCw／Al2O3复合陶瓷和金属时，陶瓷与钎料发生化学反应，在陶瓷表面形成由TiO、TiC等物相组成的反应层。采用有限元法，对SiCw／Al2O3复合陶瓷／反应层界面的热应力进行了计算。结果表明，复合陶瓷／反应层界面的残余应力变化急剧，最大拉应力位于晶须、基体和反应层交界处；晶须内部及其表面存在较高的双向压应力，Al2O3基体主要承受垂直于界面的拉应力；SiC晶须／反应层界面及其附近的反应产物TiC内具有较高的平行于界面的拉应力，当连接界面承受剪力作用时，SiC晶须／反应层界面和TiC处极易破坏。借助TEM和SEM观察了复合陶瓷／反应层界面区的精细结构和剪切断口形貌，并利用计算结果对观察到的现象进行了分析。     

Effect of infiltrating time on interfacial reaction and properties of tungsten particles reinforced Zr-based bulk metallic glass composites

The tungsten particles reinforced Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) (Vit 1 alloy) bulk metallic glass composites (BMGCs) were prepared by the melt infiltrating casting method with the infiltrating time of 1,5 and 10 min,respectively.The changes of interfacial reaction and compression properties of the bulk metallic glass composites with different infiltrating times were studied.Results show that with the increase of infiltrating time,tiny nanocrystals are generated at the interfacial boundary of tungsten particles and the amorphous matrix,and the size of tiny crystals increases with the infiltrating time.When the infiltrating time is 10 min,polygonal crystals with a larger size are also generated within the amorphous matrix.The compressive strength of the composites also increases with the infiltrating time.When the infiltrating time is 10 min,the compressive strength of the composite reaches 2,030 MPa and the compression strain is 44%.The fracture morphology of the composite materials is in a vein-like pattern and the melting phenomenon is found on the fracture surface.In addition,the density of the shear bands during the compressive tests of the composite materials increases with the infiltrating time.     

Interfacial reaction in squeeze cast SiC_w/AZ91 composites with different binders

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The failure of fiber-reinforced ceramic-matrix composites under dynamic loading

High-strain-rate compressive failure mechanisms in fiber-reinforced ceramic-matrix composite materials have been characterized. These are contrasted with composite damage development at low strain rates and with the dynamic failure of monolithic ceramics. It is possible to derive significant strain-rate strengthening benefits if a major fraction of the fiber reinforcement is aligned with the load axis. This effect considerably exceeds the inertial microfracture strengthening observed in monolithic ceramics and nonaligned composites. Its basis is shown to be the transspecimen propagation time period for heterogeneously-nucleated, high- strain kink bands. For high-strain-rate tensile loading conditions, it is found that behavior is not correctly described by the current matrix fracture/fiber pullout models. This is a consequence of the rapid and extreme frictional heating produced at the fiber-matrix interface by sliding velocities on the order of 100 m/s. At rapid loading rates, the near-interface matrix appears to virtually melt, and the frictional interface shear resistance is reduced to the point that the fibers debond throughout the specimen, and pull out without failing. This suggests that for sufficiently rapid loading, the stress to fail the composite will approach that merely to create the initial matrix crack (i.e., a stress level well below the ultimate strength normally attainable under quasistatic conditions).     

采用顶出方法研究纤维增强钛基复合材料的界面断裂韧性

为了估计单向SiC纤维增强钛基复合材料的界面断裂韧性G_IIc,本文提出了一个关于单根纤维顶出试验的新模型,在本模型中,界面脱粘开始于试样的底端面。本文以断裂力学为基础推导出了G_IIc 的理论公式,并且讨论了几个关键因素对G_IIc的影响,如裂纹扩展所需的外加应力,裂纹长度以及界面的摩擦剪切应力。并且运用此模型预测了复合材料 Sigma1240/Ti-6-4, SCS/Ti-6-4, SCS/Timetal 834 and SCS/Timetal 21s 的界面断裂韧性,并与以前的有限元结果进行了比较。结果显示,对于脱粘起始于试样的底端面的顶出试验,本模型能较可靠地预测钛基复合材料的界面断裂韧性。     

Mechanical properties of tungsten fiber reinforced ZrAlNiCuSi metallic glass matrix composite

Tungsten fiber reinforced (Zr₅₅Al₁₀Ni₅Cu₃₀)_98.5Si_1.5 metallic glass composites were fabricated and characterized. The mechanical properties of the composite under compression and tension were investigated. Tungsten reinforcement greatly increased compressive strain to failure compared to the unreinforced (Zr₅₅Al₁₀Ni₅Cu₃₀)_98.5Si_1.5 metallic glass. The compressive failure mode changed from a single shear band to multiple shear bands and to localized fiber buckling and tilting as the volume fraction of tungsten fiber increased. The maximum tensile strength and strain to failure of each of the composites were lower than those of unreinforced material due to the lack of substantial shear bands. Tensile toughness changed to some extent due to different interface reactions. The reason for the improved mechanical properties is discussed.     

Compressive strength of continuous fiber reinforced aluminum matrix composites

Aluminum matrix composites can exhibit exceptionally high compressive strength (ε 4 GPa). The main failure mechanism has been identified to be plastic kinking, although an upper bound seems to be attained when the fibers reach their compressive strength. The experimental results are consistent with a plastic kinking model in strain hardening composites. The important parameters controlling the compressive strength are the composite shear modulus, the shear yield strength, the strain hardening rate and the maximum initial fiber misorientation. Interfaces can also play an important role; composites reinforced with weakly bonded fibers have a reduced compressive strength due to their low shear strength in the fiber direction. The results can be used to design composite systems with high compressive strengths; in practice this is done by selecting matrices with high yield strengths and fast hardening rates.     

Fiber pushout and interfacial shear in metal-matrix composites

The mechanical response of a fiber/matrix interface is very important in determining the strength and the fracture behavior of metal-matrix composites. As a means of examining interfacial shear behavior, the use of the “thin-slice” fiber pushout test is becoming increasingly common. However, recent thin-slice pushout tests suggest interfacial failure processes depend not only on intrinsic factors (e.g., interfacial bond strength and toughness and matrix plasticity), but also on extrinsic factors (e.g., specimen configuration, thermally induced residual stresses, and the mechanics associated with the test). In light of these factors, this article briefly describes the contrasts in the mechanics of fiber pullout and fiber pushout. In addition, selected aspects of thin-slice fiber pushout behavior are examined to illustrate the physical nature of the interfacial shear response and its dependence on both intrinsic and extrinsic factors.