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.     

玻璃纤维增强尼龙66复合材料无人机桨叶注塑成型翘曲变形优化

针对玻璃纤维增强尼龙66复合材料无人机桨叶采用注射成型工艺制造时容易产生过大翘曲变形的问题,为减小该类零件的翘曲变形量,采用多因素正交试验法,运用注射成型模拟软件进行25次模拟试验,获得零件在熔体温度、模具温度、注射时间、保压时间、保压压力、周期时间6因素5水平下成型的翘曲变形量。通过极差分析和方差分析,确定各工艺参数对零件翘曲变形影响程度的大小排序,并得到零件的最优成型工艺参数方案。研究表明,在最优成型工艺参数方案下零件的最大翘曲变形量下降了近40%,收缩不均和取向因素是玻璃纤维增强尼龙66复合材料零件发生翘曲变形的主要原因。最后,通过对复合材料桨叶的实际制造证实了优化方案的合理性。     

基于信噪比及灰关联度的注塑工艺参数优化

针对车用开关面板在注塑加工过程中出现翘曲及收缩变形等缺陷,在正交试验的基础上,采用信噪比分析法,获得注塑加工过程中各工艺参数对优化目标的影响度。为提高工艺稳定性,采用灰关联度分析法,将多目标优化问题转换为单目标灰色关联度优化问题,由此得到最佳工艺参数组合。试验结果表明,该方法能够有效降低注塑加工过程中的缺陷,提高制品成型的质量。     

Optimization of the WEDM process of particle-reinforced material with multiple performance characteristics using grey relational analysis

This paper presents an effective approach for the optimization of the wire electric discharge machining (WEDM) process of Al₂O₃ particle-reinforced material (6061 alloy) with multiple performance characteristics based on the grey relational analysis. The machining information for the difficult-cutting particle-reinforced material is inadequate and complicated. The response table and response graph for each level of the machining parameters are obtained form the grey relational grade, and select the optimal levels of machining parameters. In this study, the machining parameters namely the cutting radius of working piece, the on time of discharging, the off time of discharging, the arc on time of discharging, the arc off time of discharging, the servo voltage, the wire feed and water flow are optimized with considerations of multiple performance characteristics, such as the surface removal rate and the maximum surface roughness. It is clearly shown that the above performance characteristics in the WEDM process are great improved together through this approach.     

短碳纤维增强铝基复合材料的挤压浸渗工艺

采用挤压浸渗法制备了短碳纤维增强铝基复合材料 ,研究了浸渗压力、铝液浇注温度、纤维预热温度等对复合材料组织的影响。结果表明 :合适的工艺参数为铝液浇注温度 740～ 80 0℃ ,预制块预热温度 35 0～ 40 0℃ ,浸渗压力 2～ 5MPa;在氩气保护下 ,无须对碳纤维表面进行涂层处理 ,可获得组织均匀的铝基复合材料。加入Al2 O3 颗粒可以改善纤维分布的均匀性     

Optimization of green sand mould system using Taguchi based grey relational analysis

The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.     

W纤维/ZrTiCuNiBeNb基金属玻璃复合材料的断裂机制

研究了W纤维/ZrTiCuNiBeNb金属玻璃基复合材料的断裂机制。结果表明:宏观上,随着复合材料中纤维体积分数的增加,复合材料的压缩断裂方式从基体控制的"自锐性"断裂向"增强体撕裂"方式转变;微观上,复合材料的断裂方式实际上只受到增强体W纤维的控制。在压缩过程中,W纤维除了受到外加应力外,还受到由于扭转弯曲、基体剪切带塞积引起的应力集中等,纤维处于一个复杂的综合应力场,当纤维内部的纤维间介变形足以抵抗这个综合应力场时,纤维处于稳定状态,复合材料中基体的变形切过纤维,复合材料表现出自锐性特征;当纤维内部的纤维间介变形不足以抵抗综合应力场时,纤维失稳,沿间介劈裂,复合材料表现出沿纤维纵向撕裂的特征。     

Experimental analysis of drilling fiber reinforced composites

In comparison with metals, long-fiber reinforced composites have a layered structure, with different properties throughout their thickness. When drilling such structures, internal defects like delamination occur, caused by the drilling loads and their uneven distribution among the plies. The current experimental analysis is focused towards determining the cutting loads distribution (axial and tangential) along the work-piece thickness and tool radius by analyzing the thrust and torque curves when drilling with 3 different drills carbon-fiber (CFRP) and glass-fiber (GFRP) reinforced composite plates. A wide range of cutting parameters is tested. The highest loads are found at the tool tip in the vicinity of the chisel edge for all cases. It is also found that the maximum load per ply varies mainly with the axial feed rate and tool geometry, while the spindle speed has little or no influence. The analysis is useful for selecting the cutting parameters for delamination free drilling and also for conducting drill geometry optimizations.     

基于正交试验的注射成型工艺参数优化方法研究

结合正交试验法和注射模拟分析软件Moldflow,对注射成型工艺参数进行优化。为获取优化的注射工艺参数组合,设计了试验方案,并对Moldflow模拟试验结果进行了极差、方差分析法处理,确定了各因素及其交互作用的主次顺序、因素之间交互作用对试验指标影响的显著程度,分析了各因素与试验指标之间的关系,得出了试验因素的最优水平和试验范围内的最优组合,即注射工艺参数组合方案,并对该工艺组合方案进行模拟和实际验证。这一研究方法对注射工艺分析与模具设计具有指导意义。     

Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials

Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials have been evaluated in the present study. The liquid metallurgy technique was used to fabricate the composites, in which preheated short glass fibers were introduced into the ZA-27 alloy melt above its liquidus temperature. The aging temperature employed was 125 °C for 6, 12,18, and 24 h. The aged alloy (no fibers) reached the peak hardness after 18 h, while the composites (regardless of filler content) reached the same hardness in 12 h. It is hypothesized that the aging treatment of a composite improves the strength of the interface between the short fibers and the matrix. This is confirmed by the tensile fractograph analysis, which indicates that at a given aging temperature, the composites aged for 18 h exhibit short fibers that remain attached to the metal matrix, while those aged for 6 h undergo debonding.     

Optimization of electrochemical polishing of stainless steel by grey relational analysis

Grey relational analysis is useful for the multi-input, discrete data and uncertain experimental study. Developed in this paper is the application of the grey relational analysis for optimizing the electropolishing of 316L stainless steel with multiple performance characteristics. The processing parameters (temperature, current density, and electrolyte composition) are optimized with considerations of the multiple performance characteristics (surface roughness and passivation strength). The conducted experiments approve the effectiveness of the grey relational analysis.     

Comparative study on the wear behavior of long and short glass fiber reinforced plastics

In recent years, the fiber reinforced composites have been used more in tribological applications where the sliding surfaces requires a high wear resistance and a low co-efficient of friction. The growth of GFRP is significantly higher than that of steel. No engineer or designer can ignore the growth of GFRP, but the decision to use a new material is difficult, yet important. The comparative tribological performance of short and long glass fiber-epoxy composites, under varying load and sliding velocities, is reported in this investigation. Besides conventional weighing, the coefficient of friction, contact temperature, and wear rate were determined. The worn surfaces of the specimens were examined by a Scanning Electron Microscope (SEM). The wear mechanisms and the transitions that govern the tribological behavior of the composites between them are discussed in detail. It was found that the epoxy reinforced with a long glass fiber exhibited a reduced wear rate than the short glass fiber.     

基于正交试验的气辅成型工艺优化

以加强筋为研究对象,对气辅成型中的熔体温度、熔体预注射量、气体注射压力、气体注射延迟时间、气体注射时间等影响气辅成型质量的主要参数进行数值模拟,并对影响塑件成型质量的相关工艺参数进行正交试验。先通过初步的五因素四水平L16(45)正交试验获得工艺参数的大致范围,然后在该基础上再进行改进的四因素三水平L9(34)正交试验,最终获得较好的工艺条件。     

Aging behavior of Al2O3 short fiber reinforced Al-Cu alloy composites

Al2O3 short fiber reinforced AI-Cu composites containing 1%, 3%, 5% and 7% Cu were fabricated by a squeeze casting technique. The as-cast Al2O3/Al-Cu composites were solution treated at 535 ℃ and then aged at 170, 190 and 210 ℃, respectively. Age hardening behavior of the Al2O3/Al-Cu composites was analyzed by measuring the hardness of the samples at different aging temperatures and aging time. Microstructures of the composites were observed by transmission electron microscope（TEM）. The results indicate that the hardness of the Al2O3/Al-Cu composites containing 7% Cu is much higher than that containing 1%-5% Cu because of the large amount of CuAl2 precipitant in the Al2O3/Al-Cu composite. With the increase of Cu content from 1% to 7%, the time needed for the appearance of peak hardness shortened, indicating that the addition of Cu can accelerate the kinetic of CuAl2 precipitation in the Al2O3/Al-Cu composites. The Al2O3/Al-Cu composite containing 7% Cu shows the highest increment of hardness by aging treatment. Therefore, in order to get a higher peak hardness, the Al2O3/Al-Cu composites need more Cu addition as compared with the un-reinforced Al-Cu alloys.     

用MPI分析注射成型工艺确定浇口数量

运用MPI模拟塑料的整个注射成型过程,在不同浇口设置的条件下,从中提取填充、保压和冷却的特征过程与参数,分析对工艺造成的影响。通过填充过程工艺参数、浇口压力曲线、螺杆速度曲线,产品重量,熔接痕,翘曲变形量等对比分析,确定了产品设置1个浇口比2个浇口更合适,达到注射过程工艺参数合理和产品质量高的目的。     

Mechanical properties of As-cast and heat-treated ZA-27 alloy/short glass fiber composites

This paper reports on the mechanical properties of as-cast and heat-treated ZA-27 alloy composites reinforced with glass fibers from 1 to 5 wt%. The composites were fabricated using the Compocasting method, in which short glass fibers were introduced into the vortex created in the molten alloy through an impeller rotated at 500 rpm. The molten mass was thoroughly stirred and poured into permanent molds and squeezed under pressure. The specimens were heat treated at 320°C for 1, 2, 3, and 4 h. The tests on the as-cast composites revealed that as the glass content in the composites was increased, the ultimate tensile strength (UTS), compressive strength, and hardness of the composite increased, while the ductility and impact strength were decreased. Heat treatment was found to improve significantly the ductility, compressive strength, and impact strength, while the hardness and UTS were reduced. This paper discusses the behavior of these composites.     

充电器上盖注射成型工艺的CAE分析

利用Mlodflow软件对充电器上盖的注射成型缺陷进行分析,通过对熔体填充、冷却、流动及塑件翘曲进行模拟,预测塑件成型过程中可能出现的缺陷,优化冷却水道、布局和浇注系统尺寸,提出优化注射方案,对优化后方案进行可行性模拟,模拟结果显示了在解决产品设计、模具设计及成型过程中存在的缺陷,具有快速、准确、方便、高效等优势,可以缩短模具制造周期,降低成本,提高生产效率。     

水辅助注塑工艺介绍

介绍了新型注塑技术——水辅助注塑工艺的基本工艺原理和工艺过程,介绍了利用可视化研究方法观察水辅助注塑成型过程中熔体和水流在型腔的填充过程。在实验室中用锁模力为800 kN的常规注射机配备水注射辅助单元进行试验,所用注射材料为半结晶状态的聚丙烯。为了研究水辅助注射中熔体和水的流动特征,特别设计了一个可视化的模具应用于这项研究。一台高速的摄像机用来记录模腔填充的过程,长方形型腔配置3种不同的流道几何布局:平面流道、一个平面带2个不同高度的台阶、一个平面带有对称的肋板。观察和研究了充模过程中水辅助和聚合物的相互作用以及水的推展过程。     

Study of cyanoethylated alfa fiber reinforced composites by dynamic mechanical analysis

Cyanoethylation of long alfa fibers was studied, and these chemically modified fibers were used to manufacture alfa-polyester composites. The dynamic mechanical thermal properties of an unsaturated polyester resin (cured) and of composites of unmodified and chemically modified alfa-polyester were studied using a dynamic mechanical analyzer over a wide temperature range. The data suggest that in spite of the fragility of the cyanoethylated alfa fibers compared to the unmodified ones, both unmodified and modified alfa-polyester composites manifest the same order of mechanical properties: T_g, tan δ and E′ values are very near in the two cases. Fragility of fibers is compensated by the better interfacial bond between the fibers and the matrix. The scanning electron micrographs of the fracture surface of the samples reveal the improved bonding at the interface between the cyanoethylated fiber and the polyester resin. The article is published in the original.     

钨丝增强Zr基非晶复合材料动态力学行为及断裂特性

采用渗流铸造法制备出d6mm钨丝增强ZrTiCuNiBe非晶合金复合材料,并利用Hopkinson压杆冲击加载装置、X射线衍射仪（XRD）和扫描电镜（SEM）等手段研究其动态压缩行为及断裂特性。结果表明：随着钨丝直径减小和体积分数的增加,材料的动态压缩强度增大;当钨丝直径为0．25mm,体积分数为60％时,材料的动态压缩强度高达2600MPa,断裂模式为剪切断裂和劈裂混合破坏模式,同时有钨丝与基体发生脱粘现象。非晶基体在动态压缩条件下表现出显著的热软化和熔化特征。