This study investigates the diffusion of synthetic fuels, plasticizers and stabilizers in pristine and aged acrylonitrile-butadiene rubber (NBR), spatially-resolved and component-selective. The objective of this study is to describe the influence of aging phenomena on the swelling of NBR in fuels in consideration of its spatial resolution, especially in small dimensions. Carbon black filled NBR with an acrylonitrile content of 18 wt% and a sample geometry of 10 x 10 x 60 mm(3) was aged thermo-oxidatively at 100 degrees C for 14 and 28 days. Hardness measurements show a spacially inhomogeneous aging behavior of the elastomer. Gravimetrical sorption experiments are conducted to describe the macroscopic diffusion behavior of synthetic fuel and the additives in NBR. Gas chromatography/mass spectrometry (GC/MS) was applied to differentiate between sorption of fuels into the elastomer and desorption of the additives out of the elastomer simultaneously and in a spacially-resolved manner. The results show a correlation between the local swelling properties and the local aging status of the elastomer. Spatially-resolved hardness investigations show a local influence of absorbed fuel on the hardness. The swelling mitigates the aging caused hardening. With a better understanding of the swelling behavior of aged elastomers the investigation aims to ensure a safe application of renewable fuels in future aviation.

Diese Arbeit weist die Freisetzung lungengängiger Kohlenstofffaserstäube aus CFC-Hochleistungsbremsen (CFC: carbon fiber-reinforced carbon, kohlenstofffaserverstärkter Kohlenstoff) nach. An einem Versuchsstand im Labormaßstab wird der Einfluss unterschiedlicher Bremsszenarien auf die entstehenden Faserstäube untersucht. Das Einschleifen der Bremsscheiben und kurzzeitige hohe Bremsbelastungen führen dabei zu besonders hohen Konzentrationen an Fasern mit kritischen Dimensionen gemäß der Definition durch die Weltgesundheitsorganisation (WHO). Hohe Temperaturen und die mechanische Belastung durch Reibung fördern den Faserabbau. Die analoge Verwendung einer Bremsscheibe aus kohlenstofffaserverstärktem Siliziumcarbid (C/SiC) führt zu höheren Faserkonzentrationen. Auch bei der Beurteilung eines Arbeitsplatzes in der Bremseninstandsetzung wurden lungengängige Kohlenstofffaserstäube detektiert, die – angelehnt an die Technische Regel für Gefahrstoffe (TRGS) 521 – einer Belastung der Kategorie 1 (Tätigkeiten mit keiner oder geringer Faserexposition) zuzuordnen sind.

This work proves the emission of respirable carbon fiber dusts from carbon fiber-reinforced carbon (CFC) high performance brakes. With a laboratory-scale test setup, the influence of different braking scenarios on the resulting fiber dust is investigated. Grinding-in of brake discs and short time high breaking loads lead to particularly high concentra tions of respirable carbon fiber dust according to the definition by the World Health Organization (WHO). High temperatures and the high mechanical load due to friction promote fiber emission. The analog use of a carbon fiber reinforced silicon carbide (C/SiC) brake discs leads to higher fiber concentra tions. Respirable carbon fiber dust is also detected within a workplace analysis during brake maintenance, classified as category 1 (activities with no or low fiber exposure) according to the Technical Rule for Hazardous Substances (TRGS) 521.

This work provides multivariate data analysis (chemometric) techniques based on infrared spectroscopy (FTIR) to separately determine temperature and duration of a moderate thermal pre-load on polymer matrix composites as well as their residual strength. The aim is to assess the precision of various techniques such as hand-held and bench top spectrometers, attenuated total reflection (ATR) and diffuse reflectance (DR) spectroscopy, as well as spectra recorded on surfaces and in the bulk of a specimen. A focus is laid on methods which are not only applicable for a single composite for which a calibration is established, but to universally apply them for epoxy based matrix systems with various thermoplastic tougheners. Therefore, data pre-treatments are investigated to focus on spectral changes which are selectively characteristic for the degradation of the thermally less stable epoxy resin. Firstly, difference spectra with pristine material are calculated and secondly, chemometric analysis is limited to spectral ranges characteristic for the epoxy resin. Commercially available composites (HexPly (R) M18-1/G939, 8552/IM7, RTM6/G939, and Cycom (R) 977-3/IM7) are investigated. Multivariate analyses provide reliable values for time and temperature (average deviation < 10 degrees C) of the thermal pre-load and residual interlaminar shear strength of specific composites (average deviation < 5%). However, average deviations dramatically increase for universally applicable methods, limiting the use of this approach.

Summary This work investigates the influence of the out‐of‐plane orientation of carbon fibers on the reaction‐to‐fire characteristics of polymer matrix composites. A deep insight into combustion processes is gained, which is necessary to fully understand and assess advantages of composites with out‐of‐plane fiber angles. Epoxy‐based Hexply 8552/IM7 specimens with primarily low fiber angles between 0° and 15° are characterized by cone calorimetry. Heat release during fire is greatly affected by the out‐of‐plane fiber angle because of the thermal boundaries created by the fibers. The advancement of the pyrolysis front during fire was determined from peak heat release rates and validated by temperature measurements along the back surface of the panels, representing a novel method of determining position‐dependent pyrolysis migration velocity. These measurements show a transverse shift in pyrolysis front velocity for increasing out‐of‐plane fiber angles. Pyrolysis pathways between the fiber boundaries facilitate faster combustion through the composite thickness, especially for increasing angles from 0° to 15°. It was determined that under the chosen conditions, the pyrolysis front advances approximately 4 times faster when propagating parallel to the fibers than perpendicular.

This study focuses on exploring the initial failure of thermally degraded carbon fibre-reinforced polymers. It is the aim of this study to provide deep insight into the damage development and propagation as well as to understand failure mechanisms of thermally degraded composites. Carbon fibre-reinforced polymer panels with different fibre orientations are exposed to heat above maximum operational temperature (up to 200 ℃) for various durations (up to ca. 200 days). Thermal degradation of the material is characterized by scanning electron microscopy and infrared spectroscopy. The onset of the failure in tension is determined by acoustic emission analysis. The results show that the development and propagation of cracks depend on the level of thermal degradation and the fibre orientation relative to the applied load. With increasing thermal degradation, transverse matrix cracking, as the prevailing initiating failure mode, is replaced by crack initiation and propagation in the damaged outermost ply independent of its fibre orientation. Severe thermal matrix degradation is limited to this area, as characterized by infrared spectroscopy. With increasing thermal degradation of the polymer matrix, the onset of crack initiation and propagation is shifted to lower strains. The effects of damage initiation on fracture behaviour are discussed.

The aim of this work was to predict composition and nine selected physicochemical properties of fossil/synthetic aviation fuel blends by chemometric analysis of mid-infrared spectra. Therefore, infrared spectra of various mixtures with six different synthetic hydrocarbon fuels were recorded and comprehensively interpreted, supported by data from comprehensive two-dimensional gas chromatography–mass spectrometry analysis of these fuels. Deep insight has been gained on how individual blend components are differentiated in principal component analysis and how they influence physicochemical properties by means of partial least squares regression. A chemometric model has been established to determine the amount of an individual synthetic fuel in a blend with a precision of <1 vol % and a detection limit of <2 vol %. The quality of prediction of physicochemical properties is good enough to compete with results obtained by established test methods.

SummaryFundamental aspects for the thermal decomposition and formation of respirable fragments of carbon fibers are investigated to assess the health hazard of carbon fiber reinforced plastic material after a fire. The influence of temperature (600°C‐900°C)/heat flux (30‐80 kW/m2), time of thermal load (up to 20 minutes), and oxygen exposure is analyzed by means of mass loss and fiber diameter of intermediate modulus and high tenacity fibers with initial diameters of 5 to 7 μm. Various types and concentrations of flame retardants were tested with respect to fiber protection. Epoxy‐based composite specimens (RTM6/G0939) additionally containing aluminum or magnesium hydroxide and/or zinc borate (1‐25 wt% per resin) were analyzed by cone calorimetry. Carbon fiber decomposition increases with combustion/irradiation time and temperature/heat flux, after a threshold temperature (ca 600°C) is exceeded. Critical fiber diameters below 3 μm are reached within minutes and are predominantly observed close to the panel surface in contact with air. Effective fiber protection is achieved by flame retardants acting beyond 600°C, forming thermally resistant layers such as zinc borate. A new field of research is opened identifying flame retardants, which protect carbon fibers in carbon fiber reinforced plastic.

Fuels are complex mixtures containing different compounds of various substance classes. Depending on the composition, particularly on the content of aromatic hydrocarbons, fuels show different swelling behavior towards elastomers. Therefore, understanding and quantitatively describing diffusion processes are essential requirements to prevent malfunctions as swelling can change material properties.To get better insight in diffusion processes, model liquids containing different amounts of dodecane and m-xylene, which represent aliphatic and aromatic fuel fractions, were used to perform sorption experiments on Acrylonitrile Butadiene Rubber (NBR). The mass uptake of each compound was traced simultaneously and time resolved by extraction and subsequent Gas Chromatography/Mass Spectrometry (GC/MS).Swelling potential of mixtures containing m-xylene and dodecane increases with higher aromatics content, which is indicated by higher equilibrium mass uptake and diffusion rate. This work provides an experimental approach to investigate interactions of fuel components and elastomers on a molecular level by quantifying diffusion processes of individual mixtures' components by GC/MS. The results allow understanding the diffusion behavior of single components in mixtures, and may be applied to compatibilityand lifetime predictions of sealing materials and in-service aviation fuels.

This work provides techniques to separately determine temperature (90–340 °C) and duration (1 minute to 240 days) of a thermal pre‐load as well as residual strength of polymer matrix composites on basis of the degradation of the top‐coat. Infrared spectroscopy and colorimetry characterizing binder degradation and colour changes of polyurethane top‐coats were used to provide a non‐destructive in‐service method to quantify incipient heat damage. A multivariate (chemometric) analysis of infrared and colorimetric data was performed. The precision of the calculated values for duration and temperature of the thermal pre‐load as well as residual strength for specimen with unknown thermal history is slightly better for the infraredspectroscopic analysis. Deviation of the calculated temperature is less than 10 °C. However, the sole analysis of colorimetric data allows a separate evaluation of these parameters. Limitations of the techniques are identified.

This work provides a comparison of analytical techniques to separately determine temperature and duration of a thermal pre-load on a polymer matrix composite as well as its residual strength. The aim is to assess selected techniques applied on surfaces and for bulk material to characterize incipient heat damage. The methods are ideally non-destructive such as infrared spectroscopy (IR). A destructive method for bulk material is represented by thermogravimetric analyses (TGA). TGA can be applied independent of accessible surfaces and inhomogeneous polymer distribution. Empirical correlations of the recorded data with mechanical properties allow the assessment of residual strength for a composite with unknown thermal history. Multivariate (chemometric) analyses provide reliable values for time and temperature (average deviation <10 degrees C) of the thermal pre-load and residual interlaminar shear strength (average deviation <5%). Bench top and hand held attenuated total reflection (ATR) and diffuse reflectance (DR) IR spectrometers provide similar accuracy. A commercially available composite (HexPly (R) M18-1/G939) was investigated. Infrared spectroscopy of bulk material after grinding is identified to provide a high potential of in-service use in aviation. (C) 2016 Elsevier Ltd. All rights reserved.

Two representative types of commercial volatile corrosion inhibitor (VCI) packaging materials without a potential for health hazards according to TRGS 615 were investigated: a paper containing ethanol amine and a polyethylene foil containing sodium nitrite as main VCI ingredients. For a variation of VCI concentration the packaging material was thermally treated at 60–100 °C and the amount of VCI remaining was determined after this accelerated desorption. Additionally a nitrite‐free polyethylene foil was impregnated with various amounts of sodium nitrite. Correlations of VCI content – of both the amine and nitrite – with corrosion protection of mild steel were observed. For ethanol amine a color change reaction is proposed to indicate the remaining potential of corrosion protection. This work is aimed at regaining trust in VCI technology.

Two commercially available carbon fibre reinforced composites (8552/IM7 and M18-1/G939) were exposed to heat above maximum operational temperature at various durations. Mass loss and mechanical properties were measured over time. A chemical analysis was also performed on these composites. The two primary components of each matrix, the epoxy resin and the thermoplastic, were observed to degrade at different rates under various thermal loading conditions. The epoxy resins degrade predominantly as measured by IR spectroscopy and thermal desorption/gas chromatography mass spectrometry. By using mass loss, strength, and IR spectroscopic data, a correlation was made between strength characteristics of each composite and the relative amount of the two primary matrix components. The developed relationship can be used to estimate rapidly the mechanical properties from the intensity ratio of IR bands characteristic of the two components.

A method based on micro attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) is described to quantify inhomogeneity of plastic components in carbon fiber reinforced plastic material (CFRP). The investigated CFRPs contain an epoxy resin and a thermoplastic. Measurements on ground specimens at an inclined plane through the material allow the determination of the polymer distribution with a resolution of one micron regarding the depth. Three commercially available CFRPs (M18-1/G939, 8552/IM7, RTM 6) are characterized providing information on mechanical and thermal properties.

AGEING TEST Plastic components made of Noryl GIN 2 were aged in heating ovens under accelerated conditions at increased temperatures and mechanically tested It is shown that the mechanical stability decreases with increasing ageing. These results are extrapolated to realistic ageing temperatures and longer times by means of the Arrhenius.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Tungstated titania catalysts (WOx/TiO2) were prepared by wet impregnation of hydrous titanium oxide hydroxide. The influences on the catalyst structure of tungsten loading tin the range of 0-30 wt % WO3 supported on TiO2), calcination temperature (varied from 473 to 973 K), and the form of the applied tungstate precursor (ammonium metatungstate or ammonium monotungstate) were investigated by surface area measurements, X-ray diffraction, thermal analysis, temperature-programmed reduction, vibrational and UV/vis spectroscopy, and X-ray absorption spectroscopy The data show that tungsten loadings giving higher than monolayer coverage of the TiO2 and the application of a high-surface-area titania precursor lead to new structural properties of the surface tungstate phase. A tungstate overlayer is formed that is stable at loadings up to ca. two monolayers (20 wt % WO3/TiO2) at a calcination temperature of 923 K. Two tungstate species are characterized by two W=O bands in the vibrational spectra. One tungstate species shows a strong dependence of its domain size and degree of condensation on calcination temperature and tungsten loading, but the other does not. The first is attributed to accessible outer segments of a three-dimensional tungstate structure and the latter to the interface providing the linkage to the TiO2 support. A three-dimensional structure is formed even at low tungsten coverages. This tungstate overlayer retards the sintering of the TiO2 support and its phase transformation from anatase to rutile. With increasing tungsten loading, the surface area-increases and the TiO2 particle sizes and pore diameters decrease. When the tungsten loading exceeds 20 wt % WO3 and the calcination temperature exceeds 923 K, WO3 is formed. These results are supposed to help to explain the properties of these materials including acidity, reactivity in reduction, and isotope exchange.