bluuebunny/crossref_metadata_2025 huggingface dataset:
Textile Reinforced Lightweight Shells
Authors: Petzoldt Carolin , Gelbrich Sandra , Röhrkohl Meike , Müller Christian , Freund Johannes , Kroll Lothar
Published: July 2015

Modern architecture is dominated by the tendency to design organically shaped filigree buildings. The resource and energy efficient construction of multifunctional buildings is as important as a broad variety of possible shapes. Multi-material support structures and shell constructions in lightweight design that also take over e. g. lighting and monitoring are needed for these purposes. Textile reinforced lightweight shell structures have been developed at Technische Universität Chemnitz within the scope of research projects. They consist of a hybrid material from carbon-fiber-reinforced concrete and glass-fiber-reinforced plastic. Thanks to the coupling of the positive material characteristics, the combination of two different composite materials results in a hybrid material with a total thickness of 15 mm, which has a high fatigue strength (XF4) and surface quality (exposed concrete). Furthermore, the hybrid is characterized by excellent compressive strength (120 MPa) and bending tensile strength (150 MPa), low susceptibility to corrosion and free formability. Therefore, it is highly suitable for thin-walled filigree lightweight shell structures. A research pavilion with a size of 4 x 4 x 3 m3 (l x w x h), made from textile reinforced lightweight shells, was built on the campus of TU Chemnitz, to test the theoretical investigations. Specially developed tensile sensors for the active lighting and determination of the elongations were integrated into the different layers. This aimed at an online-monitoring of the shell support structure.
Specific Mechanical Properties of New Hybrid Laminates with Thermoplastic Matrix and a Variable Metal Component
Authors: Nestler Daisy , Jung Heike , Arnold Sebastian , Wielage Bernhard , Wagner Guntram
Published: July 2015

Hybrid laminates combine the positive properties of metals and fibre reinforced plastics. Thereby, the relatively free selectable components provide further benefits. Especially thermoplastic matrices offer positive aspects like the possibility of deformation, recyclability as well as the possibility of mass production. To obtain such hybrid laminates the first step is the production of pre-consolidated unidirectional endless fibre reinforced thermoplastic foils. In a second step, these pre-impregnated fibre-foil tapes were alternating thermally pressed with metallic layers in tailored compositions. To use the full capacity of the hybrid laminates an adequate interface between the fibre reinforced thermoplastics and the metallic foil is essential. Different investigations of the authors display the principle possibility to produce hybrid laminates with carbon endless fibre reinforced thermoplastics and aluminium alloy foils. Nevertheless, load free delamination’s occurs. The reason for these delaminations within the interface of the fibre reinforced thermoplastics and the metallic foil are the differences in the thermal expansion coefficient of the components. Caused by the consolidation at elevated temperatures these differences become more significant and reduce the reproducibility of the hybrid laminates. To minimize these thermal induced stresses the graduation of the thermal expansion coefficient is one possibility. This graduation is possible by utilising glass fibre thermoplastic tapes between the aluminium alloy foil and the carbon fibre reinforced thermoplastics. Further investigations are dealing with so called expansion alloys to adapt the thermal expansion coefficient. The latter approach provides the benefit to utilize the full mechanical properties of the carbon fibre reinforced thermoplastics and to economize the glass-fibre tapes. Nevertheless, these expansion alloys are characterized by a high density. Hence, within this contribution the specific mechanical properties as well as the advantages and disadvantages of hybrid laminates with expansion alloys or aluminium alloys with glass-fibre thermoplastics interlayers are discussed and assessed. These specific mechanical properties display the potential of the expansion alloy in spite of the high density by means of comparable values. The sample only consisting of carbon fibre reinforced plastics highlights the great variety and possibilities of different hybrid laminate structures and combinations regarding the thickness and positioning of the component layers.
Intrinsic Lightweight Steel-Composite Hybrids for Structural Components
Authors: Modler Niels , Adam Frank , Maaß Johann , Kellner Philipp , Knothe Philipp , Geuther Marco , Irmler Christoph
Published: July 2015

Multi-Material Design has been identified to be an important enabler for lightweight structures, especially with regards to the goals for the large-scale implementation of e-mobility concepts. A novel 3D-Hybrid technology has been developed to combine the advantages of metal and fibre-reinforced thermoplastics in one structural part. This leads to significant weight reduction in combination with an increase in functionality. Additionally, the amount of single parts can be reduced; these factors combined make the technology competitive with conventional steel-sheet design. Investigations on basic profiles showed the feasibility of the technology in single stage production processes and proved the superior performance of the structure compared to conventional design. Finally, a B-pillar demonstration structure was produced in a highly automated process and investigated in side-impact related component tests.
Increasing the Structural Integrity of Hybrid Plastics-Metal Parts by an Innovative Mechanical Interlocking Effect
Authors: Müller Saskia , Brand Michael , Dröder Klaus , Meiners Dieter
Published: July 2015

In order to exploit full potential of hybrid materials, it is necessary to develop optimized load-dependent component designs, new manufacturing processes and joining technologies. Structural integrity concerning the interfaces between the single materials of the hybrid component poses a key factor to success. In this case, adhesion often constitutes the limiting factor for the maximum transferable load. In this investigation, a load-oriented innovative concept to increase the structural integrity of hybrid plastic-metal parts was developed. Local mechanical undercuts on the metal surface were created to generate an additional mechanical interlocking effect between the join partners. The aim is to find the best surface structure geometry to enhance mechanical bonding. Therefore, metal samples were structured by a new process and transferred to hybrid specimens by injection molding. For comparison, specimens with adhesive bonding (epoxy resin) of metal and plastic were prepared. The join partners aluminum AlCuMg1-2017 and PA6 as well as PA6GF30 were investigated. The evaluation of an increase in the structural integrity was determined using tensile tests. A significant improvement in joint strength compared with direct joining using adhesive bonding was achieved.
Evaluation of Corrosion Mechanisms of Hybrid Light Metal Structures by High Pressure Die Casting
Authors: Joop David , Heupel Simon , Schnatterer Christian , Zander Daniela , Bührig-Polaczek Andreas
Published: July 2015

In this study, aluminum sheet metal reinforced magnesium structures have been manufactured by high pressure die casting (HPDC). Selected interfaces of the hybrid structures were analyzed before and after exposure to corrosive environments. The characterization of the as cast bounding surfaces of aluminum sheets and magnesium cast alloys was carried out to quantify the appearance of crevices, which are significantly influencing the extent of the corrosive attack. Depending on the geometrical design of local bonding areas, the observed interface conditions varied from defect-free form closure to crevice widths beyond 35 μm. A minor percentage of the analyzed segments revealed areas of local metallic continuity, detected as intermetallic phases Al3Mg2and Al12Mg17. In order to evaluate acting corrosion mechanisms, hybrid samples featuring the material combinations EN AW 5083 + AZ91 HP and EN AW 6082 + AM50 HP were subjected to immersion tests using 0.1M NaCl solution at a pH of 7.5. The results showed a strong influence by the spread of the potential difference. Alternating corrosion tests (VDA 621-415) were applied to prove effectiveness of cathodic dip coatings (CDP) and wax sealing on standard profile structures, since the uncoated Al-Mg samples sustained severe corrosion damages immediately.
Optimization of Friction Stir Welded, Spring Steel Wire Reinforced EN AW-6082 Profile Joints
Authors: Walter Volker , Wirth Franz Xaver , Schulze Volker , Weidenmann Kay André
Published: July 2015

Composite extruded, unidirectionally spring steel wire reinforced profiles have great potential for lightweight applications. Joining of these profiles represents a difficult challenge due to the different material properties, which eliminate fusion welding as a possible joining method. Friction stir welding (FSW) has recently been used to join these profiles, the disadvantage of which is that the reinforcement elements may be bent and fragmented during welding leading to drastically reduced mechanical properties compared to non-joined profiles and even to the unreinforced matrix material. In order to minimize the disturbing influences of the reinforcement elements on the joining strength, the weld axis was shifted to the retreating side, reducing wire-pin contact at the advancing side. As a second remedial measure an insert made of matrix material was placed between the joining partners before joining in order to reduce the contact on both sides. In-situ tensile tests within an X-ray micro computed tomograph (µCT) showed that shifting the weld axis could not improve the joint quality significantly. However, the use of an insert improves the offset yield strength (Rp0.2) by about 50 %.
Lightweight Hybrid Composites of CFRP and Aluminum Foam
Authors: Fiebig Christian , Koch Michael
Published: July 2015

The lightweight potential of components made of fiber-reinforced plastic can be enhanced by use of sandwich composites. So far, limited dynamic properties of plastic-based foams have prevented the use of sandwich composites in machine applications. The combination of closed-cell aluminum foam (ALF) and carbon fiber reinforced plastic (CFRP) provides a solution to this obstacle. Aluminum foam is characterized by favorable damping properties with minimum weight and CFRP provides high strength and stiffness at similarly low density. This paper deals with the design of a hybrid sandwich composite and its interpretation by using customized FEM simulations.Producing this kind of a sandwich composite in an economic production process presents a major challenge. Thus, a method has been developed that prevents excessive penetration of the resin into the pores of the aluminum foam. A high volume fraction of the resin in the foamed sandwich core would increase density and negatively influence damping properties. The implementation of a barrier layer will avoid this penetration. A DoE was developed and RTM process parameters were varied with the objective of achieving the highest specific bending stiffness. In preliminary experiments the appropriate range of injection pressure, mold temperature, and pressure force was determined. Tests with a nonwoven fabric could prevent the resin from infiltrating into the aluminum foam. Mechanical properties of the sandwich composite are only marginally affected.A model was developed to calculate the obtainable sandwich composite properties. The calculation method considers both the characteristics of the aluminum foam and the CFRP anisotropy. Based on this model a reliable calculation of the applied load could be accomplished. The design of the sandwich composite was targeting at high stiffness and determination of the natural frequency. Parallel to calculations, tests on specimen were performed and the obtained results were included into the calculation as part of the material model.
Joining of Zirconia Reinforced Metal-Matrix Composites
Authors: Weigelt Christian , Berek Harry , Aneziris Christos G. , Eckner Ralf , Krüger Lutz
Published: July 2015

Metal-matrix composite materials, based on a metastable austenitic stainless steel reinforced with a magnesia partially stabilised zirconia have been prepared by a ceramics-derived extrusion technology. Using this powder metallurgical method enables the shaping of lightweight cellular structures as well as bulk specimens with a variety of steel/ceramic ratios at room temperature. However, the extrusion of composite structures is limited by the uniform cross section throughout its entire length. Joining of these metal-matrix composite preforms after sintering by conventional welding techniques is a challenging task. The presence of ceramic fractions may lead to several complications and the subsequent heat exposure during joining may initiate phase transformations in both metastable components resulting in a deterioration of the mechanical properties of the composite material. An adapted ceramics-derived joining technology allows the combination of varying TRIP-steel/zirconia composite materials. The main features are the machining and joining of the parts in their dry green state at room temperature before their thermal treatment. Thus, the material’s consolidation and the formation of the joint take place simultaneously. The ability of joining different parts offers the possibility to create structures for complex applications and testing conditions. The key to advanced properties of the joining zone are the base materials, the surface treatment of the parts, and the paste used for joining. The joining process of different base materials, the mechanical properties, and the microstructure of sinter-joint samples are presented.
PPS-Polymer-Composites for High Performance Rubber Components
Authors: Hickmann Rico , Diestel Olaf , Cherif Chokri , Götze Thomas , Heinrich Gert , Hürkamp André , Kaliske Michael
Published: July 2015

Based on their properties, PPS fibers are a promising material for reinforcing elastomeric components that are subjected to high mechanical and thermal loads. The use of this material is at present hindered because of the low adhesion between the fiber and matrix. Atmospheric pressure plasma treatments based on the dielectric barrier discharge were performed on PPS fibers using air as reactive gas for different treatment durations in order to improve the adhesion. The effects of these treatments have been characterized by determining the surface energy, and the residual tensile strength as well as by analyzing the surface chemistry. Required conditions for an improved wetting behavior and a significant increase in the polar component of the surface energy could then be identified.
Solvothermal Modified Layers against High Temperature Corrosion
Authors: Wöllmer Silke , Förg Andrea , Schuster Sebastian , Masset Patrick J.
Published: July 2015

Service and downtimes of waste incineration plants generate high expenses for their operators. State of the art is to protect high corrosion exposed components by cladding them with a nickel based alloy. The welded overlay is 2-3 mm thick and very expensive. It needs to be repaired at each service interval. An alternative coating consists of a thermal sprayed multilayer of a nickel based bondcoat and a ceramic topcoat. Thickness and costs of this multilayer are assumed to be in the range of about 10% of the currently used coating. A solvothermal treatment chemically densifies the coating. This leads to a significantly lower porosity whilst improving cohesion and hardness properties. This innovative process leads to a self-healing layer caused by the high temperature waste gas exposition as the driving force.
Preparation of Polymer-Derived Ceramic Coatings by Dip-Coating
Authors: Konegger Thomas , Tsai Chen Chih , Bordia Rajendra K.
Published: July 2015

Polysilazane-based coatings were prepared on dense and porous substrates by dip-coating. Both the pure, liquid polymer and polymer solutions in cyclohexane were investigated. Relevant properties of the coating solutions, including rheological properties and surface tension, were determined and used to predict the resulting layer thickness as a function of dip-coating parameters on dense borosilicate glass substrates. A good correlation between existing model (Landau and Levich) and experiment was found for the pure polymer. In the presence of a solvent, evaporation phenomena led to a predicted coating thickness that is much less than the experimental value for all dip coating withdrawal spends. The introduction of a correction factor was found to adequately describe the deviation. In case of porous substrates, the coating thickness could not be predicted using the model due to infiltration of the base structure, resulting in an interpenetrating ceramic composite layer after pyrolytic conversion of the preceramic polymer compound. When preparing polymer-derived ceramic films on porous base materials, e.g. for membrane applications, this phenomenon has to be taken into account.
Tool Life Experiments and Vibration Assistance in Regard to the Machining of CFRP
Authors: Zemann Richard , Sacherl Josef , Hake Wolfgang , Bleicher Friedrich
Published: July 2015

Molding techniques and manufacturing of components consisting of fibre reinforced polymers are mostly controlled processes. However, finishing of such materials can even today still be seen as a very challenging and not completely controlled process, which often has a non-satisfying machining quality as result. This paper deals with different topics in the field of machining FRP. On the one hand, it deals with ideas for possible evaluation mechanisms in order to classify the resulting machining quality of FRP when machining with a cutting edge. Referring to this, a framework for the definition of an international standard in measuring machining quality on FRP parts is presented. On the other hand, a possible assistance system with the aim to improve the demanding cutting process as well as a tool life experiment, are investigated. The results of these practical experiments are presented and evaluated.
High Volume Production Technology for Corrosive Resistant Long-Fiber-Reinforced Plastic Extinguishers
Authors: Tirschmann Ramon , Czäczine Jens , Hunold Mathias
Published: July 2015

Portable fire extinguishers need to be reliable and fully functional at all given environmental conditions. Especially in off-shore and power plant applications a specific range of properties is necessary, e.g. corrosive resistance and electromagnetic compatibility. Hence, the application of fiber reinforced composites and fiber composite design offers an alternative to the traditional application of metallic materials.Within the scope of the development of an innovative fire extinguisher, a process-chain for manufacturing of composite fire extinguishers suitable for aggressively corrosive environmental conditions was developed. The aim of the project has been the development of a fire extinguisher with the technology of thermoplastic composite materials. Besides the intended weight reduction, a concept for the realization of a high-volume production suitable process-chain had to be developed. Using a thermoplastic matrix material allows a corrosive-free, non-magnetic and functional integrated design. Within the scope of the research project, the extinguisher container with integrated base and connection for the valve has been dimensioned and designed. The containers geometry with optimized ratio of filling volume, overall part size and material utilization was derived by applying FE analysis. Furthermore, a process-chain for high-volume production was conceived and had been verified by producing functional demonstrators for further testing.The container is made of two glass-fiber reinforced injection molding parts being thermally joined. The leakproofness and sufficient material strength after the joining process were identified as key challenges of the joining process and were overcome with an adapted design of the molded parts. Within the process development, reproducible and high quality weld joints were achieved based on a robust and cost-efficient joining technology. For reliable processing, the specific processing parameters were analyzed and regulations for each processing step deduced.
Application of Polymer Plaster Composites in Additive Manufacturing of High-Strength Components
Authors: Junk Stefan , Matt Rebecca
Published: July 2015

Today, 3D-printing with polymer plaster composites is a common method in Additive Manufacturing. This technique has proven to be especially suitable for the production of presentation models, due to the low cost of materials and the possibility to produce color-models. But nowadays it requires refinishing through the manual application of a layer of resin. However, the strength of these printed components is very limited, as the applied resin only penetrates a thin edge layer on the surface. This paper develops a new infiltration technique that allows for a significant increase in the strength of the 3D-printed component. For this process, the components are first dehydrated in a controlled two-tier procedure, before they are then penetrated with high-strength resin. The infiltrate used in this process differs significantly from materials traditionally used for infiltration. The result is an almost complete penetration of the components with high-strength infiltrate. As the whole process is computer-integrated, the results are also easier to reproduce, compared to manual infiltration. On the basis of extensive material testing with different testing specimen and testing methods, it can be demonstrated that a significant increase in strength and hardness can be achieved. Finally, this paper also considers the cost and energy consumption of this new infiltration method. As a result of this new technology, the scope of applicability of 3D-printing can be extended to cases that require significantly more strength, like the production of tools for the shaping of metals or used for the molding of plastics. Furthermore, both the process itself and the parameters used are monitored and can be optimized to individual requirements and different fields of application.
Online Poling of Thermoplastic-Compatible Piezoceramic Modules during the Manufacturing Process of Active Fiber-Reinforced Composites
Authors: Winkler Anja , Modler Niels
Published: July 2015

Due to high specific properties and the ability for the realisation of short cycle times within the production process, the use of fiber-reinforced thermoplastic composites offers a high potential for high volume applications. Furthermore, the layered built-up and the according manufacturing processes of these materials give the possibility to integrate functional elements, like electronic components or piezoelectric sensor/actuator modules. Within the collaborative research center CRC/TRR 39 “Production Technologies for light metal and fiber-reinforced composite-based components with integrated piezoceramic Sensors and Actuators”, the integration of piezoceramic modules into lightweight structures ready for series production is investigated. This paper presents the manufacturing process of active fiber-reinforced thermoplastic composites. Here, the focus is on experimental investigations covering the process-integrated poling of novel piezoceramic modules during the manufacturing of active fiber-reinforced thermoplastic components. Therefore, laboratory and process-oriented tests are performed for the determination of appropriate parameters for the pressing and poling process. The functionality of the embedded and poled TPM is validated by the excitation of an active component structure and the optical measurement of the vibration behaviour using a laser scanning vibrometer.
Morphological Impact on the Fatigue Behaviour of Short Fibre Reinforced Polypropylene
Authors: Palmstingl Martin , Koch Thomas , Salaberger Dietmar , Paier Thomas
Published: July 2015

The fatigue behaviour of short fibre reinforced thermoplastics is highly dependent on the morphological conditions. The capability of simulating fatigue behaviour and damage mechanisms of fibre reinforced polypropylene increasingly interests industrial partners of the presented study. For the morphological analysis both destructive and non-destructive methods such as computed Xray tomography and a combination of polishing and microscopic methods were applied. The determination of the composite morphology (fibre distribution, orientation tensor, fibre length distribution) was assisted by several methods of specific automatic data evaluation concepts. Fatigue testing was done on a servohydraulic dynamic testing machine using a testing frequency of 10 Hz, which is in the range of the real loading in application of the components. The analysis included thermal investigations (IR camera) and local strain measurements.
Morphology of Sintered Cr-Mo Porous Materials
Authors: Boehm Moritz , Schmoelzer Thomas , Simon Reinhard , Gierl-Mayer Christian
Published: July 2015

Chromium and molybdenum exhibit continuous solubility in the solid phase region at temperatures of 908°C and above [1]. At lower temperatures, the system exhibits a miscibility gap. Furthermore a congruent minimum in the liquidus boundary exists at 1854°C. Chromium and molybdenum powders with different particle morphologies were mixed and porous green parts were produced by pressing. Sintering experiments were performed at different temperatures and for different chromium to molybdenum ratios. To investigate the evolution of the microstructure, sintering was interrupted at different temperatures and points in time. The microstructure and morphology of the sintered parts was investigated by scanning electron microscopy as well as light optical microscopy. It was found that during sintering, a Cr-Mo solid solution is formed. Depending on the molybdenum content, this induces either shrinking or swelling of the porous parts. Samples exhibited a linear expansion of up to 10% and final porosities of up to 65%.
Characterisation of Steel Composites Produced by the Damascus Technique
Authors: Strobl Susanne , Haubner Roland
Published: July 2015

The Damascus technique is a manufacturing process where steels with different compositions, in particular the carbon content, are forge welded. Materials with contrary properties are generated by different carbon additions: e.g., substantial toughness and elongation are combined with high tensile strength and hardness. Since the 3rdcentury AD blades and weapons have been produced by this technique in Europe.In this work various Damascus steels with different compositions were investigated by means of metallographic methods. The focus is set on the interface between individual steel layers. While the majority of interfaces look uniform and are influenced only by carbon diffusion, some areas show the enclosement of oxides and slag stringers as a result of faulty workmanship during the forge welding process.After metallographic preparation the various microstructures were characterised by light optical microscopy and confirmed by Vicker´s microhardness measurements.
Assembly Injection Molding of a Hard Component with Integrated Rubberlike Shaft Seal and Investigation of its Quality
Authors: Frick Achim , Borm Michael , Spadaro Marcel
Published: July 2015

The manufacture of a rotational shaft seal (soft component) adhesively bonded to a polymeric housing (hard component) is not state of the art. The paper approaches the feasibility to shape such hard-soft composite employing assembly injection molding technique.
Characterisation of Anisotropic Fibre Orientation in Composites by Means of X-Ray Grating Interferometry Computed Tomography
Authors: Plank Bernhard , Hannesschlaeger Christian , Revol Vincent , Kastner Johann
Published: July 2015

In this work carbon fibre-reinforced polymer (CFRP) laminates and short glass fibre- reinforced polymers (sGFRP) were investigated by means of X-ray scatter dark field imaging (SDFI) using Talbot-Lau grating interferometer computed tomography. For the characterisation of the laminate structures of CFRP the anisotropic properties of the small angle scattering signal was used to image fibre bundles running in different directions. SDFI allows the visualisation of the weave pattern structure of a carbon fibre bundle in three dimensions, even if the individual fibres cannot be separated or the absorption contrast between the carbon fibres and the epoxy resin matrix is very low. For the investigated sGFRP samples qualitative information about local fibre anisotropies within a specimen were obtained by SDFI. Due to the complex behaviour of fibre alignment during the injection process a clear interpretation of the SDFI signals was difficult. As a reference method, all samples were scanned by means of high resolution cone beam Computed Tomography (µXCT). For the sGFRP the combination of µXCT and appropriate software tools provides local fibre orientations and allows three-dimensional visualisation by colour coding each extracted fibre.
Characterization of the Mechanical and Fatigue Behavior of Braided Composites Made of Twisted Yarns
Authors: Wolfahrt Markus , Grosser Juergen , Fleischmann Martin , Schubert Matthias
Published: July 2015

In this study an experimental investigation was undertaken to characterize the influence of twisted yarns on the mechanical and fatigue behavior of 2D braided composites with a braiding angle of ±45°. Rectangular specimen made of untwisted and twisted carbon yarns are tested in the braiding (±45° fiber orientation) and in the yarn direction (0/90° fiber orientation). Experimental results will include modulus and strength values based on tensile and compression tests for both test directions. In addition, the effect of fiber twisting on S/N-curves are discussed.
Fracture Mechanics Characterization of Sintered 30 Vol.-% Al2O3/TRIP Steel Composites Using SENB Miniature Samples
Authors: Eckner Ralf , Illgen Alexander , Radajewski Markus , Krüger Lutz
Published: July 2015

Ceramic particle reinforced metal matrix composites (PRMMCs) combine the strength and brittleness of ceramics with the toughness of a metallic matrix. In order to use these materials in construction and operational design their fracture mechanical behavior must be evaluated. In this study, a 30 vol.-% Al2O3 reinforced austenitic TRIP steel processed by powder metallurgical technique was investigated using precracked miniature SENB-specimens in 3-point-bending. An elastic-plastic analysis by means of the J-integral method in combination with optical crack observation showed the materials ability of stable crack growth, i. e. R-curve behavior. In addition to the mechanical tests microstructural studies were performed, whereby particle debonding and fracture as well as martensitic phase transformation and crack bridging within the matrix were identified as fracture energy dissipating mechanisms.
Method to Quantify the Surface Roughness of Circular Reinforcing Fibres
Authors: Trautmann Maik , Nestler Daisy , Wielage Bernhard , Wagner Guntram
Published: July 2015

The properties of fibre-reinforced composites depend on the interface between the matrix and the fibre. The surface of the fibres plays a key role in the load transmission. In this article, a method based on scanning electron microscopy images of fibre cross sections is introduced to quantify the surface roughness. By utilising an image editing software to get a digital profile of the fibre contour, the arithmetic roughness Ra of a carbon fibre was calculated. The method was tested on a C-fibre with a diameter of 7 microns and compared with the images of an atomic force microscopy (AFM). The method allows a comparison of different types of fibres as well as an investigation regarding the influence of fibre treatments.
Cyclic Deformation Behaviour of Cu Multilayered Films on Si Substrates
Authors: Walter Thomas , Khatibi Golta , Nelhiebel Michael , Heinz Walther , Robl Werner
Published: July 2015

In the present study the high cycle fatigue behaviour of multilayered Cu films with different thicknesses and microstructure on silicon substrate was investigated. An ultrasonic resonance fatigue testing systems was used to study the isothermal mechanical fatigue behaviour of the Cu multilayers at room temperature and 150°C. Investigations of fatigue damage on the surface of the samples showed distinct slip band formation on preferentially oriented grains of the Cu metallization. The degree of fatigue damage, which could be related to the thickness, grain size and orientation of the Cu films, was evaluated by determination of the slip band density as a function of loading cycles. It was found that with increasing film thickness and grain size the density of deformed area strongly increases, with the majority of surface deformation occurring in the grains with ⟨111⟩ orientation with respect to the film surface. Furthermore increasing the testing temperature resulted in a significant degradation ofthe multilayered film stack due to a considerable increase in the degree of plastic deformation of theCu metallization layer.
Langerhans Cell–Dendritic Cell Cross-Talk via Langerin and Hyaluronic Acid Mediates Antigen Transfer and Cross-Presentation of HIV-1
Authors: van den Berg Linda M. , Cardinaud Sylvain , van der Aar Angelic M. G. , Sprokholt Joris K. , de Jong Marein A. W. P. , Zijlstra-Willems Esther M. , Moris Arnaud , Geijtenbeek Teunis B. H.
Published: July 2015

Human epidermal and mucosal Langerhans cells (LCs) express the C-type lectin receptor langerin that functions as a pattern recognition receptor. LCs are among the first immune cells to interact with HIV-1 during sexual transmission. In this study, we demonstrate that langerin not only functions as a pattern recognition receptor but also as an adhesion receptor mediating clustering between LCs and dendritic cells (DCs). Langerin recognized hyaluronic acid on DCs and removal of these carbohydrate structures partially abrogated LC–DC clustering. Because LCs did not cross-present HIV-1–derived Ags to CD8+ T cells in a cross-presentation model, we investigated whether LCs were able to transfer Ags to DCs. LC–DC clustering led to maturation of DCs and facilitated Ag transfer of HIV-1 to DCs, which subsequently induced activation of CD8+ cells. The rapid transfer of Ags to DCs, in contrast to productive infection of LCs, suggests that this might be an important mechanism for induction of anti–HIV-1 CD8+ T cells. Induction of the enzyme hyaluronidase-2 by DC maturation allowed degradation of hyaluronic acid and abrogated LC–DC interactions. Thus, we have identified an important function of langerin in mediating LC–DC clustering, which allows Ag transfer to induce CTL responses to HIV-1. Furthermore, we showed this interaction is mediated by hyaluronidase-2 upregulation after DC maturation. These data underscore the importance of LCs and DCs in orchestrating adaptive immunity to HIV-1. Novel strategies might be developed to harness this mechanism for vaccination.
Influence of antiplatelet-anticoagulant drugs on the need of blood components transfusion after vesical transurethral resection
Authors: Virseda-Rodríguez Alvaro Julio , Padilla-Fernández Barbara , López-Parra Mirian , Santos-Antunes Maria Tatiana , Valverde-Martínez Lauro Sebastian , Nieto-González Maria Jesus , San Miguel-Izquierdo Jesus Fernando , Lorenzo-Gómez Anabel , García-Cenador Maria Begoña , Antúnez-Plaza Patricia , Lorenzo-Gómez Maria Fernanda
Published: July 2015

Aims: The effect of the antithrombotic preventive therapy on haemorrhage keeps uncertain. We investigate the influence of the antiplatelet and anticoagulant drugs (AP/AC drugs) on the transfusion requirement after vesical transurethral resection (VTUR). We also describe the epidemiology of the blood components transfusion in our department. Materials and Methods: Retrospective observational study of a series of patients needing blood transfusion at the Urology Department between June 2010 and June 2013. Selection of 100 consecutive patients who were transfused after VTUR due to bladder transitional cell carcinoma (BTCC) (group A = GA). Control group: 100 consecutive patients who underwent VTUR due to BTCC and were not transfused (group B = GB). Transfusion criteria: Haemoglobin < 8 g/dl + anaemia symptoms. Age, gender, associated AP/AC treatment, secondary diagnoses, toxics, tumour stage and grade were analysed. Results: 212 patients required transfusion of a blood component. 169 were men (79%) and 43 women (21%). Median age 77.59 years (SD 9.42, range 50-92). Secondary diagnoses: Diabetes Mellitus 64%, high blood pressure 77%, dyslipidemia 52%. 60% of patients were previously treated with AP/AC drugs. Average Haemoglobin pre-transfusion values: 7.4 g/dl (DE ± 0.7). Average Haemoglobin post-transfusion values: 8.9 g/Dl (DE ± 0.72). Most frequent transfusion indications were bladder cancer (37%), kidney cancer (11%), prostate cancer (8%), benign prostatic hyperplasia (BHP) (8%), other urological diagnoses (36%). Intraoperative transfusions indicated by the anaesthesiologist: kidney cancer (33%), BPH (28%). Patients who underwent VTUR due to BTCC were older in GA (77.59 years SD 9.42) than in GB (68.98 years SD 11.78) (p = 0.0001). Similar gender distribution (15 women in GA and 24 in GB). Less patients were asked to keep their treatment with ASA 100mg (AcetylSalicylicAcid) in GA (25.64%) than in GB (50%) (p = 0.0330). More aggressive tumour grade in GA (p = 0.0003) and higher stage in GA (p = 0.0018) regardless of concomitant treatment with AP/AC drugs. Conclusions: The pathologies which most needed blood components' transfusions in the Urology Department were (in order of frequency): bladder cancer, kidney cancer, prostate cancer, prostate adenoma. ASA100mg did not influence the transfusion's requirements in VTUR due to BTCC. Tumour stage and higher grade have a greater influence in transfusion's requirements than concomitant AP/AC treatment. The heterogeneity of AP/AC protocols does not allow to establish the benefit of stopping those drugs before surgery in terms of avoiding blood transfusions when performing a VTUR.
Penile plaque as predictor of an advanced anorectal carcinoma: A case report
Authors: Fabiani Andrea , Filosa Alessandra , Fioretti Fabrizio , Mammana Gabriele
Published: July 2015

The secondary involvement of the penis by tumors from others organs is a rare event representing only 0.8% of overall metastasis in the genitourinary tract. The most frequent clinical findings is priapism, but occasionally, solitary metastases to the penile skin, mucosa of the glans, corpus spongiosum or lesions of the albuginea mimicking an induratio penis have been reported. We report a case of penile plaque predicting the relapse of an anorectal carcinoma. The precise etiology of this particular manifestation is not well understood and the prognosis is poor. There are no individual treatments with curative intent.
A rare complication after renal transplantation: Forgotten stent
Authors: Karabıcak Mustafa , Ipekci Tumay , Isoglu Cemal Selcuk , Keskin Mehmet Zeynel , Ekin Rahmi Gokhan , Budak Salih , Turk Hakan , Celik Orcun , Ilbey Yusuf Ozlem
Published: July 2015

In renal transplantation surgery, double J stents (DJS) are often used to reduce complications, protect the anastomosis between ureter and bladder, provide drainage in ureteral obstructions and enhance healing if there is an ureter injury. Urinary tract infections, hematuria and irritative voiding symptoms are the early complications of DJS. Migration, fragmantation, encrustation and rarely sepsis are among the late complications of DJS. In this report we describe a renal transplantation case whose DJS stent was forgotten because the patient did not attend the regular follow-up and noticed 5 years after surgery.
Die Wêreldbond van Gereformeerde Kerke, die Nederduitse Gereformeerde Kerk en ’n status confessionis teen die teologiese en morele regverdiging van apartheid
Authors: Strauss Piet J.
Published: July 2015

The World Alliance of Reformed Churches, the Dutch Reformed Church and a status confessionis against the theological and moral justification of apartheid. In 1982 the World Alliance of Reformed Churches (WARC) announced a status confessionis against the theological and moral justification of apartheid. It expelled two member churches, the Dutch Reformed Church (DRC) and the Netherdutch Reformed Church of Africa (Nederduitsch Hervormde Kerk van Afrika) because of their known support of apartheid. This situation could only be changed if these two churches were to unequivocally reject apartheid on the basis of a status confessionis and show specified practical examples of this rejection. The meaning of a status confessionis as applied by the WARC is analysed. The reason why the WARC came to a status confessionis is historically investigated. The reaction of the DRC to this resolution and its readmittance as a member of the WARC is clarified. Attention is also given to the condition that accepting a status confessionis against the support of apartheid does not mean – for the WARC at least – that a new confession of faith should follow from this.
Frailty in Advanced Heart Failure: A Consequence of Aging or a Separate Entity?
Authors: Goldwater Deena S. , Pinney Sean P.
Published: July 2015

There are over 5 million Americans with heart failure (HF), the majority of whom are over age 65. Frailty is a systemic syndrome associated with aging that produces subclinical dysfunction across multiple organ systems and leads to an increased risk for morbidity and mortality. The prevalence of frailty is about 10% in community-dwelling elderly and 20% in those with advanced HF, and increases in both cohorts with age. Yet the relationship between the primary frailty of aging and frailty secondary to HF remains poorly defined. Whether the frailty of these two populations share similar etiologies or exist as separate entities is unknown. Teasing apart potential molecular, cellular, and functional differences between the frailty of aging and that of advanced HF has implications for risk stratification, quality of life, and pharmacological and therapeutic interventions for advanced HF patients.
Conversations in African Philosophy
Authors: Chimakonam JO
Published: July 2015

Conversational philosophy is articulated by Jonathan O. Chimakonam as the new wave of philosophical practice both in “place” and in “space”. This journal adopts and promotes this approach to philosophizing for African philosophy. Readers are encouraged to submit their conversational piece (maximum of 2000 words) on any essay previously published in this journal or on any controversial topics, thoughts or authors for publication. It is recommended that conversations be on substantive issues in African philosophy rather than on metaphilosophical issues. The aim is to enhance the evolution of new epistemes in African philosophy. The subject column for the email submissions should read “Manuscript for Conversations”.
Book Review: Conversational Philosophy in Practice
Authors: Irem MO
Published: July 2015

A review of [Arguments and Clarifications: A Philosophical Encounter between J. O. Chimakonam and M. I. Edet on the Ibuanyidandaness of Complementary Ontology], 2014. 3RD Logic Option: Calabar. Paperback. Pp147Authors: Mesembe I. Edet and Jonathan O. ChimakonamDiscipline: African philosophyCategory: Ibuanyidanda PhilosophyISBN:978-978-52850-2-4Available online
Influencia de la rama de ascenso en las características de descarga de los aliviaderes de perfil estricto
Authors: Losada Miguel Ángel , Moñino Antonio , Riera Jaime
Published: July 2015

Este trabajo presenta un estudio de la influencia de la rama ascendente de la cresta del aliviadero de perfil estricto, aquél cuya geometría adopta la forma de la cara inferior de una lámina vertiente sobre vertedero en pared delgada, en el proceso de desagüe. Las alteraciones geométricas de la rama ascendente con respecto al criterio convencional de diseño propuesto por el U.S. Bureau of Reclamation, conducen a variaciones en la eficiencia de la descarga y la carga sobre la cresta, esto es, en los niveles de embalse agas arriba. Partiendo de la formulación analítica del problema del vertedero, se identifican tres regímenes característicos de funcionamiento, vertedero somero, intermedio y profundo, el último de los cuales gobierna el funcionamiento de la mayoría de aliviaderos de presas. Bajo este enfoque, se ha desarrollado un programa experimental que ha permitido cuantificar la influencia de la geometría del perfil en el régimen, de descarga, encontrándose una nueva geometría de diseño simple que garantiza igual o mejor respuesta hidráulica que la del perfil clásico. Se ha verificado experimentalmente, no obstante, que la mejora en la descarga no supone un riesgo de daños por cavitación.
Simulazione numerica tridimensionale del campi de moto indotti dal vento
Authors: Cioffi Francesco , Gallerano Francesco , Napoli Enrico
Published: July 2015

Nell’articolo viene proposto un modello numerico tridimensionale al volume finiti, che viene utilizzato per la simulazione di campi di moto indotti dal mento in corpi idrici con batimetria complessa. I risultati numerici sono confrontati con misure sperimentali. Al fine di verificare gli effetti sul calcolo del campi idrodinamici di alcume ipotesi simplificative, relative alla distribuzione verticale della pressione e degli sforzi di Reynolds, sono stati quindi condotti alcuni test numerici, dai quali si è evidenziato che l’ipotesi di distribuzione idrostatica delle pressioni, cui si fa ricorso nelle approssinazioni di tipo “quasi-3D”, può essere utilizzata per il carcolo del profili verticali della componente di clocità orizaontale ad una certa distanza dalle pereti, ma conduce a risultati poco corrtti in prossimità delle pareti di monte e di valle. Si è inotre verificata l’applicabilità del modello algbrico proposto da Tsanis [23], confrontando il profilo parabolico del coefficiente di viscosità tubolenta assunto da questo mmodello con quello resultante dall’utilizzo del modello K. Tali profili risultano in buon accordo nella maggior parte del dominio considerato, sebbene il modello di Tsanis sobrastimi decisamente le viscosità turbolente in prossimità delle pareti di monte e di valle.
Metodologia de apoio ao diagnóstico para amelhoria do desempenho de sistemas de distribuiçao de água
Authors: Dias Nuno , Covas Dídia Isabel , Ramos Helena
Published: July 2015

Este trabalho consistiu na aplicação do conceito de desempenho hidráulico para a avaliação do comportamento de um sistema de distribuição de agua, em termos de pressões, velocidades de escoamento e perdas de água. Numa primeira fase, procedeu-se a concepção e ao dimensionamento do sistema em análise de acordo com a regulamentação em vigor, utilizando o ferro fundido dúctil. De seguida, compararam-se os desempenhos hidráulicos do sistema com os referentes a outras soluções alternativas para diferentes materiais das condutas (i.e., polietileno de alta densidade e policloreto de vinilo), diferentes factores de consumo (l e., regulamentares e específicos de uma determinada zona) e configurações do sistema.