静水压力对触变挤压Csf/AZ91D复合材料变形及纤维取向的影响

在触变挤压过程中,通过施加静水压力（即背压）可以有效地控制纤维取向,从而改善短纤维增强复合材料的机械性能。本文试验研究了有、无背压情况下Csf/AZ91D复合材料触变挤压过程中变形场及纤维取向变化规律。基于流函数法获得了Csf/AZ91D复合材料触变挤压过程中的等效应变速率,结合图像处理技术,对挤压后纤维取向角度度进行了统计分析,探讨了背压对塑性变形区尺寸,塑性变形区内应变速率的分布以及纤维取向角度的影响。结果表明,不施加背压情况下,从坯料外壁到心部存在明显的等效应变速率梯度,在相同位置,纤维取向角度与等效应变速率几乎成正比关系,而施加背压提高了坯料充填模具外侧拐角的能力,使得坯料横截面上等效应变速率梯度变小,分布更加均匀,纤维取向角度也更加一致。研究结果对于调控Csf/AZ91D复合材料的塑性变形具有重要的指导意义。     

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.     

Effect of compressibility on flow field and fiber orientation during the filling stage of injection molding

The anisotropy caused by the fiber orientation that is inevitably generated by the flow during the injection molding of short fiber reinforced polymers, greatly influences the dimensional accuracy, the mechanical properties and other qualities of the final product. Since the filling stage of the injection molding process plays a vital role in determining the orientation of the fiber, an accurate analysis of the flow field for the filling stage becomes a necessity. Unbalanced filling occurs when a complex or a multi-cavity mold is used, leading to the development of regions where the fiber suspension is under compression. It is impossible to make an accurate calculation of the flow field during filling within analysis assuming an incompressible fluid. In this study, a FEM/FDM hybrid scheme with consideration of compressibility was developed to calculate the flow field. At the moment of complete filling, the three-dimensional fiber orientation field was estimated by solving the equation of orientation change for the second-order orientation tensor with the fourth-order Runge-Kutta method. A mold with four cavities with different filling times was produced to compare the results of numerical analysis with experimental data. There was good agreement between the experimental and theoretical results when the compressibility of the polymer melt was considered for the numerical simulation. Also, qualitative and quantitative comparisons of fiber-orientation states for compressible and incompressible fluids were made.     

模压压力对2D-Cf／SiC复合材料性能的影响

以聚碳硅烷、SiC微粉为原料，二维碳纤维织物为增强体，采用先驱体转化法制备了2D-Cf／SiC复合材料，考察了模压压力对2D-Cf／SiC复合材料常温力学性能的影响。结果表明，随着模压压力的增加，纤维体积分数明显提高，但材料的力学性能未能随之提高，主要原因在于随着压力增加，SiC微粉对碳纤维的损伤加剧。模压压力的增加导致纤维体积分数增加和纤维损伤的加剧，两方面的原因造成模压压力对材料的力学性能影响不大。有压成型比无压成型制得的材料的高温抗氧化性要好，主要原因是在0MPa压力下，材料基体更容易出现裂纹，从而使得高温条件下氧化气氛更容易对材料性能造成损害。     

液态浸渗后直接挤压铝基复合材料的力学性能

实验研究了采用液态浸渗后直接挤压工艺制备的氧化铝短纤维增强铝基复合材料（Al2O3Sf／Al）的力学性能。发现该方法制备的复合材料不仅具有很高的弹性模量和强度性能、材料中增强纤维的增强承载作用得到了充分发挥,而且延伸率能保持在相对较高水平。结果表明,该工艺是一条非常有效的制备金属基复合材料的新途径。     

碳纤维增强复合材料双面埋头压铆模拟分析

铆接技术作为一种不可拆卸的连接方式,在飞机装配过程中被广泛使用，同时碳纤维增强复合材料由于自身优异的力学性能也成为了航空工业中热门。在碳纤维增强复合材料铆接的过程中,铆钉的变形会对铆接的碳纤维增强复合材料造成损伤,从而影响铆接的质量以及其使用寿命。针对这一问题，使用有限元仿真软件ABAQUS创建复合材料双面埋头压铆三维模型，通过ABAQUS子程序接口编写VUMAT用户材料自定义程序，分别取Hashin准则和Puck准则的优势作为三维失效准则，选用合理的刚度退化方式对压铆后的复合材料的渐进损伤进行分析。通过ABAQUS对复合材料压铆过程模拟，得到铆钉在压铆过程中的成形规律和复合材料层合板的主要损伤失效形式为基体的压缩和拉伸、纤维压缩以及其损伤失效的扩展方向。     

汽车前地板后本体复合模压成形工艺

针对汽车前地板后本体在线复合模压成形工艺,探究采用螺杆机混合浸润挤出的LFT-D高温坯料与单向碳纤维预浸料增强片的多元复合模压过程,通过正交实验法,研究复合模压成形的主要工艺参数(入模料温、模压压力、合模速度和保压时间等)对成形缺陷的影响,结合力学性能实验进行筛选,确定出了优化后的成形工艺组合参数为:单向碳纤维预浸料增强片的入模料温为100℃、模压压力为5000 kN、合模速度为10 mm·s^-1、保压时间为40 s。将有单向碳纤维预浸料增强片与无增强片的前地板后本体产品进行对比,在相同测试条件下进行冲击和拉伸力学性能实验,结果表明,1.3 mm的单向碳纤维预浸料增强片可以将厚度为2 mm的LFT-D产品的纵向抗拉强度和冲击韧性提高7~8倍。     

粉末冶金热挤法制备无钯镀镍碳纤维增强镁基复合材料及组织观察

利用粉末冶金热挤压技术制备短碳纤维增强镁合金复合材料。为了改善碳纤维与基体的润湿性,对碳纤维进行表面无钯化学镀镍处理。通过扫描电子显微镜(SEM)观察碳纤维化镀层以及碳纤维镁基复合体的形貌,通过超景深金相显微镜观察纤维在复合材料中的分布并对复合材料的挤压过程进行分析。结果表明:镀镍碳纤维能满足制备的要求并有利于纤维在复合体中的均匀分散,在含4.0%(质量分数)碳纤维的预制体采用压制压力为420MPa,烧结温度为550℃保温0.5h后,在480℃用280MPa的压力进行热挤压得到材料的力学性能最佳。     

Optimization of the injection molding process of short glass fiber reinforced polycarbonate composites using grey relational analysis

This paper presents a fast and effective methodology for the optimization of the injection molding process parameters of short glass fiber reinforced polycarbonate composites. Various injection molding parameters, such as filling time, melt temperature, mold temperature and ram speed were considered. The methodology combines the use of the GRA (grey relational analysis) method and a CAE flow simulation software, to simulate the injection molding process and to predict the fiber orientation. This method can replace the traditional “change-one-parameter-at-a-time” approach, which is very inefficient, costly, time consuming and almost impracticable to yield an optimum solution. At the same time, the fiber orientation was examined by CAE simulation to forecast the shear layer thickness, and simultaneously to check the accuracy of the GRA. The results indicated that three distinct layers (a frozen layer, a shear layer and a core layer) are observed from the surface to the core for various injection molding conditions. The fiber orientation is perpendicular to the melt flow direction in the frozen layer and the core layer, but it has the opposite direction in the shear layer. From the CAE analysis, the optimum process parameters to obtain the thickest shear layer are found, which is the target of the present research.     

Effect of applied pressure on mechanical properties of squeeze cast mg matrix composites

The present study aims at investigating the correlation of microstructure and fracture properties of two AZ91 Mg matrix composites fabricated by squeeze casting technique with a variation of the applied pressure. The composites were reinforced with Kaowool alumino-silicate short fibers and Saffil alumina short fibers, respectively. Microstructural observation, fractographic observation, andin situ fracture tests were conducted on these composites to identify the microfracture process. From thein situ fracture observation of the Kaowool reinforced composites, microcracks were initiated at the short fiber/matrix interfaces for the composite processed with the lower applied pressure, whereas microcracks were initiated easily at short fibers already cracked during squeeze casting at the very low stress intensity level for the composite processed with the higher applied pressure. Thus in this case. the effect of the applied pressure on mechanical properties could be explained using a competing mechanism; the detrimental effect of fiber breakage might override the beneficial effect of the grain refinement and the densification as the applied pressure was increased. On the other hand, for the composites reinforced with Saffil short fibers, microcracks were initiated mainly at the fiber/matrix interfaces at the considerably high stress intensity factor level while the degradation of fibers was hardly observed even in the case of the highest applied pressure. This finding indicated that the higher applied pressure yielded the better mechanical properties on the basis of the reinforcing effect of Saffil short fibers having excellent resistance to cracking.     

Fatigue crack growth behavior and fiber orientation of glass fiber reinforced polycarbonate polymer composites

The use of polymer-based composites has become increasingly common in the aeronautical and automotive industries. In this study, the fiber orientation of polymer composites was observed using microtoming techniques and the fatigue behavior of these composites was experimentally studied under mechanical loading. This involved the mechanical properties for parent and weld parts of polycarbonate (PC) composites in a tensile test and SEM. It was found that the tensile and hardness properties depended on the fiber orientation in the parent and weld parts of PC composites. Fatigue crack growth behavior depending on the fiber orientation was different in the parent and weld parts, according to a low cyclic-loading test.     

Analysis of Microstructures and Mechanical Properties of Particle Reinforced AlSi7Mg2 Matrix Composite Materials

The present study examined the microstructures and mechanical properties (tensile and impact strength, hardness) of selected metal matrix composite materials. SiCp reinforced AlSi7Mg2 matrix composites were produced using gravity and squeeze casting methods and subsequently T6 heat treated. Some of the squeeze casted composites were shaped by extrusion. The extrusion generated an equiaxed matrix structure and SiCp caused a homogeneous distribution. The quasi absence of porosity in the squeeze casted composites led to improved mechanical properties. Whereas an increase in the SiCp ratio resulted in an increase of the tensile strength, it led to a decrease of the impact strength values. The enhancement of the mechanical properties following an applied heat treatment was better for materials shaped by extrusion.     

微-纳米SiC/聚丙烯复合材料的制备与力学性能

SiC具有优异的力学与功能性能,作为增强相,在复合材料领域具有广阔的应用前景.采用双螺杆挤出、注塑成型方法制备了微-纳米SiC/聚丙烯(PP)复合材料.分别采用硅烷(KH-550)和钛酸酯(NDZ-201)两种偶联剂对微米(10 ìm)和纳米(50 nm) SiC复合粉体进行表面处理,研究了偶联剂、SiC粉体粒度及添加量对SiC/PP复合材料的弯曲强度、冲击强度、弯曲模量、弹性模量和热变形温度的影响.结果表明,经KH-550/NDZ-201混合偶联剂改性的微-纳米SiC粉体共同增强PP材料的综合力学性能最好,其弯曲强度、冲击强度、弯曲模量、弹性模量和热变形温度比纯PP材料分别提高了40%,8.7%,141%,142%和33%.经钛酸酯改性的SiC/PP复合材料的力学性能优于硅烷和混合偶联剂(KH-550/NDZ-201)改性的SiC/PP复合材料.     

热固性预浸料模压成型工艺参数实验研究

通过研究热固性预浸料模压成型(Propreg Compression Molding,PCM)复合材料层合板制备过程中固化压力与树脂流失量之间的关系,对比不同树脂含量的预浸料在模压成型后的力学性能,发现最佳力学性能对应的预浸料树脂含量为38%。为了进一步提高PCM模压制品力学性能的稳定性,将模压后树脂含量保持在38%的固化压力作为固定参数,对模具温度和固化时间进行了16组正交实验,检测层合板的力学性能,并分析树脂与纤维织物界面之间的微观结合情况。结果表明:当固化压力为3800 kN时,可以将树脂含量为40%的预浸料在模压后的树脂含量控制在38%左右,并在模具温度为155℃、预热时间为40 s、保压时间为440 s时,得到抗拉强度为520.18 MPa、冲击韧性为32.35 J·cm^-2、综合力学性能最好同时微观缺陷最少的样品。经现场工艺验证,实验得到的规律和工艺参数组合可应用于热固性复合材料汽车电池包上盖的批量生产中。     

FeCrAl纤维对FeCrAl(f)/HA复合材料显微结构及力学性能的影响(英文)

采用热压工艺制备FeCrAl纤维增强的FeCrAl(f)/HA生物复合材料,通过金相显微镜、X射线衍射、扫描电子显微镜(SEM)以及能谱(EDS)等测试手段对试样的微观结构及成分进行观察和表征。采用三点抗弯法测定FeCrAl(f)/HA复合材料试样的力学性能。研究结果表明:复合材料的性能随FeCrAl纤维加入得到提高,并随着纤维含量(0～11%,体积分数)的增加逐渐明显下降。HA基体和FeCrAl纤维界面结合紧密,互相咬合较深,并在两相上出现了一定程度的互扩散。FeCrAl(f)/HA生物复合材料的最优化参数如下:纤维直径22μm,长度1-2mm、体积分数7%左右。     

施镀条件和热处理对铝合金 Ni-P-SiO2 复合镀层微观结构及显微硬度的影响

目的提高Ni-P镀层的硬度。方法在化学镀Ni-P过程中添加SiO2微粒,形成Ni-P-SiO2复合镀层,研究施镀温度、微粒添加量和镀后热处理温度对复合镀层微观结构及硬度的影响。结果复合镀层含非晶结构Ni和SiO2相。随施镀温度的升高及SiO2微粒添加量的增加,镀层表面变得均匀、致密且硬度升高,显微硬度最高达355HV;当施镀温度超过80℃,微粒添加量超过10 g/L时,镀层表面均匀性变差,硬度下降。经热处理后,镀层向晶态转变,热处理温度达到300℃时开始析出Ni3P相,镀层的显微硬度随热处理温度的升高而升高。结论当施镀温度为80℃、微粒添加量为10 g/L时,所得复合镀层的性能较为优异,热处理可进一步提高复合镀层的硬度。     

国产芳纶上浆剂对聚三唑复合材料力学性能的影响

目的研究国产芳纶纤维DAF-III表面上浆剂的主要成分及其对复合材料界面性能的影响。方法用丙酮溶剂抽提纤维一定时间,分析对比去除上浆剂前后的纤维和抽提溶液,并制备DAF-III增强的聚三唑树脂复合材料,测试复合材料的力学性能。结果国产DAF-III芳纶纤维的主体结构是聚酰胺苯并咪唑,表面上浆剂主要组分是脂肪族酯类低聚物。溶剂抽提去除了纤维表面大部分上浆剂,裸露的纤维本体存在制备过程中形成的沿纤维方向的大量沟壑;去除上浆剂后,复合材料的ILSS和弯曲强度分别提高了181.2%和56.20%。结论纤维表面上浆剂对纤维以及纤维增强的复合材料力学性能影响显著,纤维与树脂通过机械锚合和氢键作用改善界面粘接。     

Rapid 3D microwave printing of continuous carbon fiber reinforced plastics

Using microwave heating in 3D printing of continuous carbon fiber reinforced plastic (CCFRP) instead of the traditional resistive heating constitutes a new approach for the additive production of high performance composite components. Without the intrinsic slow speed and contact-needed heat transfer disadvantages, the instantaneous and volumetric heating benefits of microwave allows the fabrication of composites at higher speed. This paper presents the 3D microwave printing technology for CCFRP and investigates the mechanical properties of the tensile specimens that have been printed with different speeds. The printing process and mechanical properties of printed specimens are investigated and discussed.     

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

SiC_p/AZ91镁基复合材料的热挤压

采用搅拌铸造法制备SiC体积分数为5%、10%和15%的颗粒增强AZ91镁基复合材料（SiCp/AZ91）。复合材料经过T4处理后,于350°C以固定挤压比12：1进行热挤压。在铸态复合材料中,颗粒在晶间微观区域发生偏聚。热挤压基本上消除了这种偏聚并有效地改善颗粒分布。另外,热挤压有效地细化基体的晶粒。结果表明：热挤压明显提高复合材料的力学性能。在挤压态复合材料中,随着SiC颗粒含量的升高,基体的晶粒尺寸减小,强度和弹性模量升高,但是伸长率降低。