PP/GMT片材骨架材料——玻纤毡

玻璃纤维毡种类及其结构对熔体浸渍、片材孔隙率、力学性能及预热膨化有着很大影响。实验研究表明,PP熔体浸渍连续针刺玻纤毡的渗透率较大,所得片材孔隙率最低,且具有均衡的力学性能。说明连续玻璃纤维原丝针刺毡的立体弹性结构有利于熔体的浸渍和气泡的排除,是较理想的GMT增强材料。     

A Dielectric Sensing Approach for Controlling Matrix Composition During Oxide-Oxide Ceramic Composite Processing

Continuous fiber reinforced ceramic matrix composites (CMC’s) made from aluminum oxide fibers and matrices are usually fabricated using a tape casting process. In this process, ceramic slurry consisting of the oxide powder, a polymeric binder and a solvent is infiltrated into a woven ceramic fiber mat. After evaporation of some of the solvent, the resulting flexible tapes can be stacked and sintered to create a composite component. Because the fraction of ceramic powder in the slurry can vary during processing, in-situ compositional sensors are required for on-line feedback control to limit property variations in the composite material. Since the dielectric properties of the slurry components are distinctly different, the effective permittivity of the slurry depends upon its composition. Here, a non-contact capacitance probe has been used to explore the possibility of capacitance sensing for compositional control. Results indicate that the removal of solvent during a precision drying step may be monitored by this approach. The feasibility of monitoring changes in the slurry’s composition during infiltration of the fiber mat is also discussed.     

Monitoring of Corrosion Under Insulations by Acoustic Emission and Humidity Measurement

We simultaneously monitored humidity and AE from active corrosion under insulation (CUI). For humidity monitoring, we developed an optical fiber sensor based on the moisture dependency of absorption of laser light by connecting coating of polyvinyl alcohol and CoCl₂ coating and pullulan coating in series on the fiber as a cladding layer. The sensor could be used to measure humidity of 65–95% RH at 80°C. The temperature dependence of the sensor was as small as 2.5% RH/10°C. We monitored active CUI by the acoustic emission technique and humidity sensing under wetting and drying cycles. Most AE signals were produced during the drying process in each wetting and drying cycle, and the AE rate increased with the time of wetness (period of humidification).     

Processing of Thermoplastic Composites Using a Powder Slurry Technique. II. Coating and Consolidation

Powder impregnation techniques have been developed to increase design and manufacturing flexibility with thermoplastic composites. This paper presents an experimentally based analytical investigation of the coating and consolidation processes of powder impregnated tows. Polymer flow during towpreg manufacture was studied and the various stages of fiber coating were identified. A coalescence model was developed to predict the degree of coalescence of the powder as a function of the processing parameters. The stiffness of the final towpreg was found to be related to the extent of coating of the fibers with the powder. A consolidation apparatus was fabricated to determine the effect of key processing variables upon the degree of consolidation of the towpreg. The plaques produced from the consolidation experiments were evaluated using 3-point flexure tests and image analysis. The influence of each parameter and parameter interaction was determined.     

Effect of rapid curing process on the properties of carbon fiber/epoxy composite fabricated using vacuum assisted resin infusion molding

Long processing cycle makes vacuum assisted resin infusion molding (VARIM) only suitable for low and medium volumes of production, and shortening of curing time is critical to improving the processing efficiency of automotive composite parts. In this paper, unidirectional carbon fiber reinforced composite laminates were fabricated by VARIM. Three different processes (namely quick, quick-post and preheating) were employed, in which a kind of rapid curing epoxy resin is used. The preheating of mold and fiber was conducted to shorten the filling time compared with that of quick process. Quick-post process with a post cure stage was investigated to verify the composite properties fabricated by quick process. The cycle time was 16 min for preheating process, about 30% shorter than that of quick process, simultaneously, flexural strength and interlaminar shear strength (ILSS) were respectively improved by 29% and 7% compared with those of quick process. The non-uniformity of mechanical properties at different positions along resin flow direction under preheating process was found, but the processing quality of composite was good. The preheating process is confirmed to be suitable for the improvement of processing efficiency of VARIM with good mechanical properties. In addition, the composite fabricated by quick-post process has better mechanical properties, which is attributed to the alleviation of residual stress during post curing process.     

Characterizing microstructure of refractory porous materials

Liquid Expulsion technique was used in this study to quantify the transport properties and microstructure of a refractory coating used in the Lost Foam Casting process. The pore size information obtained from the Liquid Expulsion Method is found to be well correlated with the transport properties of the porous coating material. For manufacturing process control, the viscosity of these coating slurries prior to its application on expanded polystyrene foam is often reduced by dilution with water and/or using a dispersant. In this paper, the effects of diluting or dispersing the slurry on the microstructure and transport properties of the dried refractory coatings are evaluated. Results show that the dilution and dispersion have opposing influences on the pore size and transport properties. Adding dispersant was found to reduce the transport properties of the refractory coatings significantly, potentially leading to defects in metal castings. The pore characterization technique developed in this paper is also used to determine the effects of drying methods (oven versus air dry) on the pore size and transport properties.     

超细HMX的真空冷冻干燥工艺优化及性能表征

为改善超细硝胺类炸药浆料的干燥效果,采用单因素实验法和响应面实验设计法,综合分析了真空度、浆料厚度以及分散液中乙醇与水的质量比等主要工艺参数对超细HMX浆料干燥过程的影响规律,建立了超细HMX的最佳干燥曲线拟合模型,获得了最优干燥工艺参数。同时,结合实验进行验证,并采用扫描电子显微镜（SEM）和撞击感度仪分别对干燥前、后超细HMX的微观形貌及安全性能进行了测试、分析。结果表明:超细HMX浆料的干燥速率随真空度的增加先增大后减小,随浆料厚度的增加先减小后增大,随乙醇与水的质量比的增加而增大;超细HMX浆料真空冷冻干燥的优化工艺为:浆料厚度7 mm、真空度50 Pa、乙醇与水质量比0.4;工艺优化后的超细HMX颗粒分散性好,无团聚,安全性不变。     

Semi-solid Pressing Bonding Strength between Steel and Cu-graphite Composite

The pressing bonding of steel plate with QTi3.5-3.5graphite slurry was studied. The relationship among preheating temperature of steel plate, preheating temperature of dies, solid fraction of QTi3.5-3.5graphite slurry, and interfacial shear strength of bonding plate could be established with artificial neural networks perfectly. This model could be optimized with a genetic algorithm. The results show that the optimum bonding parameters are: 618℃ for preheating temperature of steel plate, 526℃ for preheating temperature of dies and 46.2% for solid fraction of QTi3.5-3.5graphite slurry, and the largest interfacial shear strength of bonding plate is 128.3 MPa.     

Revealing the formation mechanism of granules by drying simulation of slurry droplet

The formation mechanism of granules in spray drying process was investigated by DEM-CIP method simulation coupled with a new binder segregation model. To confirm the validity of proposed binder segregation model, experiment on drying of aqueous slurry containing fine particles and binder was performed. The experimental concentration distribution of binder in a dried powder bed agreed well with the simulated one and this result shows that the proposed segregation model is valid to represent segregation phenomenon in the dried granule. Spherical hollow granules were formed with increasing of binder concentration, and the granules were depressed in higher concentration of binder. When the binder concentration in the surface region of a slurry droplet increased during drying, a crust of granule was formed because particle migration was hindered by high fluid viscosity. For the rigid crust layer, granules were hollow. When the crust layer was formed early in drying and its thickness was thin, granule surface partially collapsed inward, whereas the granule resulted in depression granules.     

碳纤维/尼龙6预浸料的制备及盒体的热冲压成型工艺

首先利用自主设计的熔融浸渍机头制备了60 mm幅宽的连续碳纤维增强尼龙6（CF/PA6）热塑单向带,并利用快速热冲压成型技术制备了CF/PA6复合材料矩形盒体。结果显示,在CF/PA6预浸料制备过程中,纤维展纱包覆角与纤维展宽呈线性关系;预紧力增加展纱宽度的同时,牵引力会呈指数急剧上升,因此应避免大的预紧力;CF/PA6预浸料的浸渍质量随牵引速度的增加而降低;预热有利于改善高浸渍速度下的浸渍质量。在热冲压成型过程中,CF/PA6复合材料的最佳预热温度为260~280℃,模具温度为130~160℃,并应经过预压实。      

Experimental Study of Heat Transfer Performance of Polysilicon Slurry Drying Process

In recent years, the growth of the solar energy photovoltaic industry has greatly promoted the development of polysilicon. However, there has been little research into the slurry by-products of polysilicon production. In this paper the thermal performance of polysilicon slurry was studied in an industrial drying process with a twin-screw horizontal intermittent dryer. By dividing the drying process into several subunits, the parameters of each unit could be regarded as constant in that period. The time-dependent changes in parameters including temperature, specific heat and evaporation enthalpy were plotted. An equation for the change in the heat transfer coefficient over time was calculated based on heat transfer equations. The concept of a distribution coefficient was introduced to reflect the influence of stirring on the heat transfer area. The distribution coefficient ranged from 1.2 to 1.7 and was obtained with the fluid simulation software FLUENT, which simplified the calculation of heat transfer area during the drying process. These experimental data can be used to guide the study of polysilicon slurry drying and optimize the design of dryers for industrial processes.     

用 Sol—Gel 法制备碳纤维的 SiO_2涂层

本文提出了一种在碳纤维表面获得 SiO_2涂层的溶胶-凝胶法。用硅酸乙脂的乙醇溶液,经水解、缩聚、干燥和焙烧而在碳纤维表面形成抗氧化和抗扩散的均匀 SiO_2涂层。对涂层的形貌、构成及用涂层碳纤维增强的 Mg 合金作了讨论。     

聚丙烯旋转成型浆液料的干燥行为

研究了以粉状聚丙烯(PP)为原料、以羧甲基纤维素(CMC)为稳定剂的旋转成型用水性浆液料的干燥行为.实验结果表明,PP/CMC浆液料体系由于CMC的成膜作用而导致干燥过程复杂化,表现出与普通干燥过程不同的特点.出现了该体系所特有的变速干燥阶段.     

Experimental investigation and modelling of the temperature effects on the tensile behavior of textile reinforced refractory concretes

The work in hand presents results of an experimental and numerical research on the post-heating residual strength of a basalt textile refractory composite submitted to tensile loading. The tensile tests were performed after a preheating process at temperatures ranging from 25 to 1000 °C. The mechanical performance and cracking mechanisms were discussed and compared to that obtained at room temperature. Image analysis by means of digital image correlation method was used to obtain the evolution of crack width which was subsequently correlated with the stress response for all target temperatures. Scanning electron microscopy was used to investigate the damage processes in the fiber–matrix interfaces after exposure to high temperatures. A finite difference model was used to simulate the tension stiffening behavior of TRC (Textile Reinforced Concrete) systems predicting their crack spacing and stress vs. strain responses. The obtained results indicated that due to the coating decomposition the reliability of basalt TRC can only be guaranteed from room temperature to 150 °C.     

Implementation of quality by design approach in manufacturing process optimization of dry granulated,immediate release,coated tablets – a case study

The aim of this study was to optimize the process of tablets compression and identification of film-coating critical process parameters (CPPs) affecting critical quality attributes (CQAs) using quality by design (QbD) approach. Design of experiment (DOE) and regression methods were employed to investigate hardness, disintegration time, and thickness of uncoated tablets depending on slugging and tableting compression force (CPPs). Plackett–Burman experimental design was applied to identify critical coating process parameters among selected ones that is: drying and preheating time, atomization air pressure, spray rate, air volume, inlet air temperature, and drum pressure that may influence the hardness and disintegration time of coated tablets. As a result of the research, design space was established to facilitate an in-depth understanding of existing relationship between CPPs and CQAs of intermediate product (uncoated tablets). Screening revealed that spray rate and inlet air temperature are two most important factors that affect the hardness of coated tablets. Simultaneously, none of the tested coating factors have influence on disintegration time. The observation was confirmed by conducting film coating of pilot size batches.     

热塑性树脂连续浸渍过程的纤维断裂机制及实验

利用自行设计的浸渍模具,通过拉挤熔融浸渍工艺,定量考察了牵引速度、熔体温度和浸渍辊个数等工艺参数对连续玻璃纤维增强热塑性复合材料复合过程中纤维断裂的影响,旨在通过所建立的纤维断裂数学模型,预测预浸料生产过程中纤维断裂率并描述实验结果。结果表明:模型与实验数据吻合较好,能够为工业化生产提供指导与借鉴;纤维束在模具中拖曳而产生的黏性剪切作用是影响纤维断裂的主要因素,适当减少浸渍辊数及采用低黏度树脂能够显著降低纤维断裂,提高工艺稳定性。     

3-D stamp forming of thermoplastic matrix composites

In this investigation a mould with hemispherical cavity and 80 kN hydraulic press, allowing variable stamping speeds, are employed for experimentally studying of the 3-D stamp forming process of continuous fiber reinforced thermoplastic laminates. In particular, glass fiber (GF) reinforced polyetherimide (PEI) woven fabric made of sheath surrounded, polymer powder impregnated fiber bundles manufactured by Enichem, Italy, is used. Pre-consolidated laminates are heated by contact heating in an external heater up to about 120°C above the glass transition temperature (T _g) of the polymer matrix; they are then stamp formed in a cold matched metal tool. Typical cycle times (including preheating time of the preconsolidated laminates) are in the range of 3 min. Useful processing conditions, such as stamping temperature, stamping velocity and hold-down pressure required for stamp forming of this composite are determined. In addition the effect of die geometries (deformation radian) and original laminate dimensions are studied. The results describe the correlations between processing parameters and fiber buckling. Finally the thickness distribution in stamped parts are investigated in relation to different directions of fiber orientation.     

抗菌食品包装纸的研究现状及发展趋势

目的对国内外食品抗菌包装纸的研究现状进行综述分析,总结食品抗菌包装纸的技术发展趋势,以期为抗菌纸的研究提供有效参考。方法对抗菌食品包装纸的抗菌剂——无机型抗菌剂、化学合成型抗菌剂、天然抗菌剂及其主要抗菌机理进行阐述;根据涂布、添加浆料、浸渍/喷淋、纤维改性等加工方法对抗菌食品包装纸进行分类;分析和总结国内外食品抗菌包装纸的最新研究成果;从高效安全抗菌剂及应用剂型的研发,抗菌纸抗菌效果的持久性和作用方式的提升,食品抗菌包装纸的产业化工艺技术的开发等方面指出今后食品抗菌包装纸的发展趋势。结果食品抗菌包装纸的开发仍处于初步阶段,抗菌纸的产业化推广不够,抗菌纸中抗菌剂的安全性、稳定性、可持久性还有待进一步改善。结论随着对绿色安全高效抗菌剂、应用剂型和抗菌纸加工技术的进一步研究,食品抗菌包装纸必将得到更广泛的推广应用。     

Hollow fiber optics with improved durability for high-peak-power pulses of Q-switched Nd:YAG lasers

To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light.     

空心叶片内孔道防护工艺的研究

以用于空心叶片外表面的ＡＳＬ－５水溶性扩散型料浆铝－硅涂层工艺为基础，研究了叶片内孔道料浆注入防护工艺。研究结果表明，ＡＳＬ－５料浆采用注入法用于叶片内孔道防护，涂层覆盖率可达１００％，涂层厚度均匀，无烧结，堵孔现象，而且通过适当调整料浆成分可使内孔道的涂层组织，成分和外表面涂层完全一致。