Interlaminar fracture toughness of woven fabric composite laminates with carbon nanotube/epoxy interleaf films

The Mode I interlaminar fracture behavior of woven carbon fiber/epoxy composite laminates incorporating partially cured carbon nanotube/epoxy composite films has been investigated. Laminates with films containing carbon nanotubes (CNTs) in the as‐received state and functionalized with polyamidoamine were evaluated, as well as laminates with neat epoxy films. Double‐cantilever beam (DCB) specimens were used to measure G_Ic, the critical strain energy release rate (fracture toughness) versus crack length. Post‐fracture microscopic inspection of the fracture surfaces was performed. Results show that initial fracture toughness was improved with the amino‐functionalized CNT/epoxy interleaf films, but the important factor appears to be the polyamidoamine functionalization, not the CNTs. The initial fracture toughness remained relatively unaffected with the incorporation of neat epoxy and as‐received CNT/epoxy interleaf films. Plateau fracture toughness was unchanged with the use of functionalized CNT/epoxy interleaf films, and was reduced with the use of neat epoxy and as‐received CNT/epoxy interleaf films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanism of seeded dispersion polymerization of methyl methacrylate using submicron polystyrene seed particles

Submicron polystyrene (PS) latex particles were used as seed in seeded dispersion polymerization of methyl methacrylate (MMA) to investigate the particle nucleation and aggregation behavior in this type of polymerization. The PS seed particles were located and tracked during the reaction using a refractive index matching technique. The number of PS seed particles present in the poly(methyl methacrylate) (PMMA) particles was investigated in detail throughout the reaction. The change in the distribution of PMMA particle populations containing different numbers of seed particles indicated that intensive nucleation and aggregation occurred during the early stage of the reaction until a transition point of 8.7% conversion was attained under the reaction conditions studied. The size of the large particles at this point was around 1 μm. These particles were regarded as mature particles that did not aggregate with other mature particles. Meanwhile, immature particle were still generated continuously from the continuous phase. These immature particles could not survive the aggregation process to grow to become mature particle, but instead, were captured by the mature particles. Therefore, the total number of the mature particles remained constant from this point until the end of the reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of near-infrared absorbing composites comprised of conjugated macroligands on the surface of PbS nanoparticles

We report a facile macroligand strategy towards the synthesis of low-bandgap inorganic-organic composites comprised of semiconductor PbS nanoparticles and functional copolymers. For this, thiol-functional thiophene-based macroligands have been used as coligands for PbS nanoparticles. Thus, solution processable organic-inorganic hybrid materials with absorption in the near-infrared have been obtained. The resulting nanoparticle-polymer composites were characterized in detail by optical and FT-IR spectroscopy as well as TEM showing their potential as novel functional inorganic-organic hybrid materials when applied in initial proof-of-concept hybrid photovoltaic devices.     

Partial Discharge Measurement of OCP-Tapes in Rotating Electrical Machines

Nowadays, PD （partial discharge） measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the user are interested in the results of PD measurements. However, PDs hardly represent the cause of the failure, more likely they are claimed as the outcome of a failure. This paper deals with the insulation of a 6 kV electrical machine, whereas PD measurements were carried out at a single stator from wound coils. During manufacturing, these coils were equipped with different materials for the OCP （outer corona protection）. Using different PD measurement systems and different bandwidths, investigations of the PD behavior of the coils were carried out. Additionally, the surface resistivity of the corona protection was determined. As a result, conclusions for the correlations between the resistance of the OCP as well as the PD behavior are stated. Furthermore, the influence of using different measurement systems, different measuring circuits, and different bandwidths is shown.     

PROBABILISTIC MODELLING OF LIGNIN LIQUEFACTION

ABSTRACT

The results of the thermal and catalytic reactions of lignin model compounds are used in the a priori prediction of its liquefaction. Lignin was defined probabilistically as an ensemble of single ring aromatics with substituents on each of their six ring positions. Elements in a substituent vector x¹, for each ring position i, were matched into all possible combinations to describe lignin. Initial number fractions, or probabilities, for each vector element were ascertained through inspection of lignin structural data. The reaction of lignins altered the probabilities within each substituent vector, and reaction products were also calculated by matching all combinations of vector elements for each ring position. Model compound results provided the identities and rates of change of vector elements.

This simulation of lignin liquefaction predicted the yields of permanent gases, aqueous liquids, single- and two-ring phenolic products, and a carbonaceous residue. The impact of the distribution of oligomeric sizes on catalyst effectiveness was probed.     

Occurrence of benzene as a heat-induced contaminant of carrot juice for babies in a general survey of beverages

A survey of benzene contamination of 451 beverage samples, using headspace sampling combined with gas chromatography and mass spectrometry (HS-GC/MS) with a quantification limit of 0.13 µg l^?1, was conducted. Artefactual benzene formation during headspace sampling was excluded by gentle heating at 50°C only and adjustment of sample pH to 10. The incidence of benzene contamination in soft drinks, beverages for babies, alcopops and beer-mixed drinks was relatively low, with average concentrations below the EU drinking-water limit of 1 µg l^?1. Significantly higher concentrations were only found in carrot juice, with the highest levels in carrot juice specifically intended for infants. About 94% of 33 carrot juice for infants had detectable benzene levels, with an average concentration of 1.86?±?1.05 µg l^?1. Benzene contamination of beverages was significantly correlated to iron and copper concentrations, which act as catalyst in benzene formation. The formation of benzene in carrot juice was predominantly caused by a heat-induced mechanism, which explains the higher levels in infant carrot juices that are subject to higher heat-treatment to exclude microbiological contamination.     

用于经济型使用的多轴加工中心

作为世界最大的汽车供应厂商之一的大陆公司(Continental)要按照他们全球顾客的需求生产,将来的生产设备也同样必须灵活地适应客户需求的变化。从这个意义来说,SW公司已经为大陆公司开发了一种"世界机床"。作为全球汽车供应的重要厂商,大陆公司远远超出了车辆构件的制造和按时交货的能力。这里,专有的组件和标准部件的OEM方式(来件组装)摆脱了开发和生产各种成套汽车部件的困境。这样,在46个国家约有173000员工的情况下,     

Thermal performance testing of flat-plate collectors

Existing standards for testing the performance of flat-plate solar collectors are documented in ASHRAE 93 [ANSI/ASHRAE Standard 93-2003, 2003. Methods of Testing to Determine Thermal Performance of Solar Collectors, ISSN: 1041-2336, ASHRAE, Inc., 1791 Tullie Circle, Ne, Atlanta, GA30329], ISO 9806-1 [ISO Standard 9806-1:1994(E), 1994. Test Methods for Solar Collectors – Part 1: Thermal Performance of Glazed Liquid Heating Collectors Including Pressure Drop, ISO, Case Postale 56, CH-1211 Geneve 20, Switzerland] and EN12975-2 [European Standard EN12975-2:2001, 2001. Thermal Solar Systems and Components – Solar Collectors – Part 2: Test Methods, CEN, Rue de Stasart, 36, B-1050, Brussels]. The ASHRAE 93 standard requires an experimental determination of the steady-state collector efficiency under prescribed environmental conditions for a range of collector fluid temperatures. Each test requires a minimum of 20 min and 22 tests are required to fully characterize a collector’s thermal performance. The ASHRAE 93 testing procedure is further complicated by the fact that the prescribed weather conditions do not often occur in some locations, which prolongs the time required to conduct the performance tests for a given collector. The EN12975-2 collector test procedure provides an alternative transient test method that can be conducted over a larger range of environmental conditions. This paper compares the results obtained by applying the EN12975-2 standard with results obtained from the ASHRAE 93 steady-state tests for a well-designed single-glazed selective surface flat-plate collector. The collector thermal parameters, F_R(τα)_e and F_RU_L obtained by the two test methods show good agreement. The incident angle modifier coefficient determined in the ASHRAE method, which uses a separate test for this purpose, was found to be more accurate than that determined in the transient method according to the EN12975-2 standard, which obtains this value and all other collector parameters in the same step. This transient method, however, uses a refined collector model that includes specific terms for the wind speed dependence and the collector thermal capacitance, which are absent in the ASHRAE model. The long-term collector thermal performance as a part of a water heating system was simulated using the efficiency curves derived from each of the test methods. The solar fractions obtained by simulation are within 7% for both cases.