bluuebunny/crossref_metadata_2025 huggingface dataset:
Impacts du vécu de la reconversion professionnelle des ouvrier.ère.s de l’industrie sur leur identité
Authors: Cocandeau-Bellanger Laurence , Fonteneau Alice
Published: July 2017

Cet article présente une recherche sur des adultes anciennement ouvrier.ère.s de l’industrie ayant vécu une reconversion professionnelle suite à un licenciement économique et qui se sont engagé.e.s vers un nouveau métier. Il rend compte de la façon dont ces personnes, contraintes de devoir abandonner un métier, perçoivent cette reconversion et construisent leur identité professionnelle. L’objectif est d’identifier l’impact de cette perception de la reconversion sur leur construction identitaire. Une enquête qualitative réalisée auprès de onze personnes a permis de modéliser les résultats autour, d’une part, de trois profils-types identitaires d’ouvrier.ère.s reconverti.e.s : être auteur.e.s, acteur.rice.s ou assujetti.e.s et d’autre part, de deux modèles-types de construction identitaire : coopérative ou conflictuelle.
Of Exodus and of Rapture: A Theological Reading of the Openings of Battlestar Galactica by Glen Larson (ABC, 1978) and the Reimagined Series by Ron D. Moore (Sci-Fi, 2003)
Authors: Caron Caroline-Isabelle
Published: July 2017

The theological dimension of the pilot mini-series (2003) of the reimagined Battlestar Galactica (Ron D. Moore, Sci-Fi, 2003-2009) sharply contrasts with that of the original series (Glen Larson, ABC, 1978-1979). In the original BSG, the last humans are in Exodus, and cross the desert-that-is-space in search of the promised land of Earth. In the reimagined series, the pilot mini-series is more clearly apocalyptic and points to contemporary forms of dispensionalism, and especially, belief in the Rapture.
Modeling and Analysis of Friction Stir Welding and Underwater Friction Stir Welding of Aluminium Alloy: A Review
Authors: Shanavas S. , Dhas J. Edwin Raja
Published: July 2017

The welding of aluminium and its alloys was a great challenge for researchers and technologists till 1991. Friction stir welding (FSW), a relatively new solid state joining process was first patented in 1991 by Thomas et. al. from ‘The welding Institute (TWI), England. Later its application found in various industries like aerospace, marine, automobile, etc. due to its high quality joints. The technique is energy efficient, ecofriendly and versatile too. In this review article, the modeling and analysis of friction stir welding and underwater friction stir welding (UFSW) of aluminium alloy are addressed. Commonly used method for modeling and analysis of welded joints such as Taguchi method and Response surface method (RSM) are considered for the review. Finally an attempt has been made to compare UFSW welded joints with FSW welded joints.
Effect of Reinforcement and Tribological Behaviour of AA 7068 Hybrid Composites Manufactured through Powder Metallurgy Techniques
Authors: Lakshmipathy J. , Rajesh Kannan Subburaj , Manisekar K. , Vinoth Kumar S.
Published: July 2017

In this article, an attempt was made to study the mechanical behaviour of AA7068 - 6 vol. % of MoS2 - X vol. % of WC (X = 0, 5, 10 and 15) hybrid aluminium composites produced by blend–press–sinter methodology. Compacted Powders (700MPa) were sintered at different temperatures (450 0c, 500 0c and 550 0c ) in order to find the influence of sintering temperature on mechanical properties and tribological behavior of AA7068 hybrid composites.The sintered samples have been characterized by x-ray diffraction (XRD) method for identification of phases and also to investigate the phase changes. The change in density, hardness and porosity values of composites were reported. The composite with 15 vol. % of tungsten carbide and 6 vol. % of MoS2 showed the highest hardness and density at the sintering temperature range of 550 0c. Pin-on-disc type apparatus was used for determining the wear loss occurring at different conditions. The hybridization of the two reinforcements enhanced the wear resistance of the composites, especially under high applied load, sliding distance and sliding speeds. Due to this, the hybrid aluminium composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, predominantly in the aerospace and automotive engineering sectors. The morphology of the wear debris and the worn out surfaces were analyzed to understand the wear mechanisms.
Performance and Emission Analysis of a Ci Engine Fuelled with JOME-JOEE-Diesel Blends
Authors: Sankar Shanmugasundaram , Manivarma V. Kumaresan , Thampi Arun
Published: July 2017

In this study a high viscous liquid fuel, approximately 20 times more than that of diesel, produced from non- edible oil seed jatropha curcaswhich has been considered as an alternative fuel for the compression ignition engine is reduced through trans-esterification process. During this process, the raw jatropha curcas oil is preheated to 60°C and treated with methanol 20% by volume along with potassium hydroxide (KOH) by 0.568% of the oil weight as alkaline catalyst at 60°C reaction temp to produce Methyl Esters of Jatropha Oil (JOME). Similarly, the above method is followed to produce Ethyl Esters of Jatropha Oil (JOEE) with preheating at 70°C. In addition, 2% glycerol is added to the mixture to improve the reaction rate. The lower viscous fuel biodiesel (JOME and JOEE) produced by trans-esterifying of jatropha oil is blended with pure diesel 50% by volume. An experimental investigation have been carried out without altering the CI engine to examine the performance parameters in terms of brake thermal efficiency, total fuel consumption and brake specific fuel consumption for several engine load from 0 Kg to 8 Kg. The study also includes, separation of crude biodiesel from glycerol, washing of crude biodiesel, examination of calorific value using bomb calorimeter, viscosity measurement using redwood and brookfield viscometer, engine emission test and cost comparison for production of one litre of JOME and JOEE. It is inferred from the above study that the blends of JOME with diesel have closer performance to diesel when compared to the blend of JOEE with diesel. But, on comparison of their exhaust emission, the JOEE showed reasonable lower exhaust emission CO and NOx in spite of its higher calorific value when compared with JOME. The study also revealed that the biodiesel can be adopted as an alternative fuel for existing diesel engine without any modification.
Energy Saving Method for Operating CNC Machine Door
Authors: Gayathri N. , Shanmuganathan V.K. , Karthigayan K.G. , Manesh Kumar S.
Published: July 2017

Energy is an important aspect in our day to day life. It is important to save energy wherever possible that to electric energy. We are suffering from electric energy crisis now-a-days. In order to save electric energy alternate system is chosen and it is implemented which would save electric energy. Wasting energy for supplementary or supporting works like machine door opening and closing considered as uneconomical. Energy consuming system consumes lot of energy for supporting works. In this energy saving concept two different types of system can be coupled to work as a single system which would save much energy than before. Our concept discusses about the same. Energy wastage for operating CNC machine door is taken for consideration in our work and analysis has been done on it. A new hydraulic operating system is proposed to overcome the difficulties.
Delamination in Drilling of Sisal/Banana Reinforced Composites Produced by Hand Lay-Up Process
Authors: Saravana Kumar A. , Maivizhi Selvi P. , Rajeshkumar L.
Published: July 2017

Natural fiber composites are presently replacing the synthetic fiber in many fields. The present research work study is an attempt to manufacture and test the sisal/banana fiber reinforced polymer composites. Composite have been manufactured using banana and sisal fiber along with epoxy resin as reinforcement. With these composites drilling has been carried out to study the factors and combination of factors that influence the delamination of drilled unidirectional sisal-banana fiber reinforced composites. Drilling experiments were performed based on the L9-Taguchi method. Delamination factor evaluated for the selected parameters spindle speed, feed and diameter of the drill tool with the help of signal to noise ratio, ANOVA analysis and to obtain the conditions for minimum delamination.
Sustainability Analysis of Prototyping Processes
Authors: Jayakrishna Kandasamy , Sanjay Guar P. , Senthilkumar R. , Aathis Nagarajan
Published: July 2017

Development of prototypes draws major focus in contemporary manufacturing organisations. Sustainability analysis and comparison of the prototype manufacturing process plays a vital role in deciding the sustainability level of the product. Sustainability of prototyping depends on model building material and model building process. In this paper based on the customer requirements, Environmental Conscious Quality Function Deployment (ECQFD) was carried out. Increased lives, strength, reduced toxicity of material with biodegradability were the major outputs of ECQFD. Cambridge Engineering Selector (CES) and Grey Relation Analysis (GRA) were used for material selection. Wood, ABS, Poly Lactic acid (PLA) and Lead were selected as cost efficient materials for the case product. A CAD model of the case product was developed and subjected to Life Cycle Analysis (LCA) using solid works sustainability express for the above materials. Prototypes of the case products where produced by wood carving, casting, CNC Milling and 3D printing by considering all input parameters required across each process. LCA was conducted using GaBi for the above process and the results were compared. From this study, it was observed that the case product developed using PLA with 3D printing technology had very less impact on environment and is considered as the best and cost effective prototyping method.
The Effect of Ceramic Reinforcement on the Microstructure, Mechanical Properties and Tribological Behavior of Al-7.5%Si-0.5%Mg Alloy
Authors: Avinash L. , Kumar Hemanth , Parthasarathy Adithya , Varun Kumar K.N. , Sajjan Basavaraj
Published: July 2017

In this investigation, A357 (Al-7.5%Si-0.5%Mg) alloy/Al2O3 composites with various weight fractions (4%, 8%, 10%) were prepared by using permanent mould casting. In addition, A357 alloys were cast for comparison purposes. Microstructure, hardness and tensile properties of these composites were evaluated and compared with as-cast alloy. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus at a constant sliding velocity of 1m/s and pressure of 0.35 MPa. The microstructure of the composites shows homogenous distribution of Al2O3 plate-like particles in the Al matrix except in the A357/10%Al2O3 composite. The wear and mechanical properties of composites improve with increasing the weight percentage of Al2O3 upto 8% and then decreases. Particularly, mechanical properties of the A357/10%Al2O3 composite are lower than the alloy indicating that the critical weight fraction of Al2O3 reinforcement in the A357 alloy is 8%. Wear morphology studies show that higher wear rate in case of unreinforced specimen was associated with higher thickness of hardened layer and consequent delamination of wear debris from the surface which was confirmed by optical and scanning electron micrography.Whereas ductile and brittle mode of fracture is observed in Fractographic observation of composite. The present paper highlights the salient features of casting technique and characterization of aluminum alloy A357 and alumina metal matrix composite.
Scheduling of Machines and Automated Guided Vehicles in FMS Using Gravitational Search Algorithm
Authors: Nageswararao Medikondu , Narayanarao K. , Rangajanardhana G.
Published: July 2017

A new meta-heuristic gravitational search(GS) algorithm is proposed for simultaneous scheduling of machines, and two identical automated guided vehicles(AGVs) in a flexible manufacturing system(FMS). It minimize the makespan and completes the assigned jobs faster with possible savings of the resources. The adequacy of the algorithm is demonstrated by solving several problems and comparing with existing results.
Fabrication and Characterization of Al-0.4%Si-0.5%Mg - SiCp Using Permanent Mould Casting Technique
Authors: Parthasarathy Adithya , Avinash L. , Varun Kumar K.N. , Sajjan Basavaraj , Varun S.
Published: July 2017

Production of A6063/SiC composite with various weight fractions (3%, 6%, 9%) were prepared by using permanent mould casting was investigated. The preferred mean particle size of SiC is 60 μm. In addition, A6063 alloys were cast for comparison purposes. The alloys and composites were given a T6 heat treatment process (solution treatment at 520 °C, water quenching at room temperature and artificial ageing at 180 °C), Also Microstructure, hardness and tensile properties of these composites were evaluated and compared. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus with various parameters (constant load of 10N and varying velocities as follows 0.5m/s, 1m/s, 1.5m/s, 2m/s) .The microstructure of the composites shows homogenous distribution of SiC particles in the Al matrix except in the A6063/9% SiC composite. The wear and mechanical properties of composites improve with increasing the weight fraction of SiC Wear morphology studies show that higher wear rate in case of unreinforced specimen compared to heat treated composites. Whereas with the increase in SiC content, the material tends to fail in brittle mode. The aim of present study is to evaluate the effect of heat treatment on the mechanical and tribological properties of aluminum alloy A6063 /SiC metal matrix composite.
Effect of Mechanical Properties on Various Surface Treatment Processes of Banana/Cotton Woven Fabric Vinyl Ester Composite
Authors: Umachitra Chitra , Palaniswamy N.K. , Shanmugasundaram O.L. , Sampath P.S.
Published: July 2017

Natural fibers have been used to reinforce materials in many composite structures. Many types of natural fibers have been investigated including flax, hemp, ramie, sisal, abaca, banana etc., due to the advantage that they are light weight, renewable resources and have marketing appeal. These agricultural wastes can also be used to prepare fiber reinforced polymer hybrid composites in various combinations for commercial use. Application of composite materials in structural applications has presented the need for the engineering analysis. The present work focuses on the fabrication of polymer matrix composites by using natural fibers like banana and cotton which are abundant in nature and analysing the effect of mechanical properties of the composites on different surface treatments on the fabric. The effect of various surface treatments (NaOH, SLS, KMnO4) on the mechanical properties namely tensile, flexural and impact was analyzed and are discussed in this project. Analysing the material characteristics of the compression moulded composites; their results were measured on sections of the material to make use of the natural fiber reinforced polymer composite material for automotive seat shell manufacturing.
Optimization of Material Removal Rate in Wire-EDM Using Fuzzy Logic and Artifical Neural Network
Authors: Ashok R. , Poovazhagan L. , Srinath Ramkumar S. , Vignesh Kumar S.
Published: July 2017

Present work aims to develop a model and optimize the material removal rate (MRR) in complex wire electric discharge machining (EDM) process. Initially various percentages of aluminium alloy hybrid Nanocomposites were fabricated by novel ultrasonication method. The sample specimens were cut and machined using wire EDM. Experiments were carried out using Taguchi’s L18 orthogonal array under different cutting parameters like Pulse-on, Pulse- off, current and servo voltage. Fuzzy-based Taguchi method and artificial neural network (ANN) with back propagation algorithm were used to optimize the material removal rate. Both ANN and fuzzy logic based models were developed in MATLAB software and the models were trained for estimating the MRR and improving the machining parameter.
Manufacturing of Hard Composite Materials on Fe-Base with Oxide Particles
Authors: Brust Sebastian , Röttger Arne , Kimm Janis , Usta Erkan , Theisen Werner
Published: July 2017

Metal matrix composites (MMC) are often applied to tool surfaces to increase resistance to wear and tear. However, some matrix and particle materials such as Ni, Co, WC or TiC are expensive and partly classified as critical elements. With respect to tribo-mechanical properties, Fe-alloys reinforced with oxide particles are promising compound materials to produce wear-resistant MMC with low-cost and readily available materials. However, thus far the technical application of such MMCs is limited due to poor wettability of the oxides by Fe-base melts and an associated weak bonding between the oxide particles and the metal matrix phases. In this work two novel production techniques (namely pre-metallization and active sintering) are introduced, which improve the wettability and interfacial reactions between both materials and therefore enable supersolidus liquid-phase sintering (SLPS) of the MMC. For the first technique the oxide particles are pre-metallized by depositing a thin film of TiN on the surfaces. The second technique is called active sintering. For this technique the alloy design is adapted from active brazing, so that wettability of the oxide particles by the alloy-melt is increased. The resulting effects of these techniques are investigated using wetting and sintering experiments, and are analyzed with respect to the developed microstructures and interfacial reactions between the oxide particles and the metallic phases.
High Strain Rate Compression Testing of Hot-Pressed TRIP/TWIP-Matrix-Composites
Authors: Eckner Ralf , Krüger Lutz
Published: July 2017

Metal matrix composites with ceramic reinforcements such as particles or fibers have come into focus during the past decades due to rising requirements on engineering materials. In this work, composite materials out of high-alloy CrMnNi-steel matrices with varying Ni-contents (3 wt.% and 9 wt.%) and 10 vol.% Mg-PSZ were processed by hot-pressing. The variation in Ni-content resulted in a change in stacking fault energy (SFE) which significantly influenced the deformation mechanisms. The mechanical behavior of the developed composites was investigated in a wide strain rate range between 0.0004 s-1 and 2300 s-1 under compressive loading. This was done by a servohydraulic testing system, a drop weight tower, and a Split-Hopkinson Pressure Bar for the high strain rates. To study the influence on the deformation mechanisms such as martensitic transformations and/or twinning, interrupted tests were also carried out at 25 % compressive strain. Subsequent microstructural examinations were done by a magnetic balance to measure the quantity of α’-martensite as well as by scanning electron microscopy (SEM). The results show an increase of strength and strain hardening with decreasing SFE of the matrix due to increased α’-martensite formation. The addition of the Mg-PSZ particles resulted in further strengthening over almost the entire deformation range for all investigated composites. At high strain rates quasi-adiabatic heating suppressed the martensite transformation and reduced the strain hardening capacity of the matrix. Nonetheless the particle reinforcement retains its strengthening effect.
Composite Peening - A Novel Processing Technology for Graded Reinforced Aluminium Matrix Composites
Authors: Seitz Michael , Reeb Andreas , Klumpp Alexander , Weidenmann Kay André
Published: July 2017

Recently, the attention paid to Metal Matrix Composites (MMCs) has increased markedly. In particular, particle-reinforced MMCs are outstanding due to superior specific properties and their wear resistance. In order to further improve material utilization, recent investigations with local reinforcements in highly stressed component sections, the so-called Functionally Graded Metal Matrix Composites (FGMMC), are concerned. The production of such FGMMC was realized with composite peening - a modified process on the basis of micro shot peening. Due to this solid-phase process, ceramic particles can be introduced into regions close to the boundary layer. As preliminary studies on tin show, ceramic particles can be introduced close to the specimen surface even at room temperature. By varying process parameters, in particular by increasing the temperature, the penetration depth of the particles can be significantly increased. In case of aluminium as base material, an input of particles into the surface could be observed at a process temperature of 150 °C. The combination of aluminium with reinforced ceramic particles makes this process interesting for lightweight, wear-resistant and cyclically highly stressed structural components. Using composite peening to produce FGMMCs is a novel, economic approach.
Mechanical Properties of Aluminum-Matrix-Nanoparticle-Composites
Authors: Kasakewitsch Alla , Arlic Uwe , Riehemann Werner
Published: July 2017

Aluminium-Matrix-Nanoparticle-Composites were produced by ball milling of micro scale Aluminium powder with various nanoscales ceramic powders like Silicon Carbide, Alumina and Boron Nitride with subsequent consolidation by hot extruding. The composites were investigated by amplitude dependent damping tests, tensile tests at elevated temperatures, hardness measurements, imaging methods and electric conductivity tests. All tested samples were machined out of hot extruded rods. The Amplitude dependent damping of bending samples was determined by measuring the strain dependent logarithmic decrement of free decaying vibrations of bending beams at room temperature. These tests were done after successive step by step isochronal heat treatments. Some samples show substantial improvement of the mechanical properties due to dispersion hardening or grain refinement. It can be concluded that the results are mainly influenced by dislocation effects like Orowan-effect, work-hardening, grain-size-hardening, recrystallization, and creation of dislocations at ceramic particles due to thermal mismatch. Moreover some results can be attributed to fatigue during mechanical cycling namely crack nucleation, crack growth and fraction. The electric conductivity was measured indirectly by permeability tests with a digital hysteresis recording devise. The results show the low influence of nano-particle dispersion hardening to conductivity in comparison of work-hardening.
Continuous Powder Extrusion for Fabrication of Carbon Fibre Reinforced Aluminium
Authors: Saefkow Martin , List Matthias , Schubert Andreas , Lohmüller Andreas , Singer Robert F.
Published: July 2017

Short fibre reinforced aluminium was produced using the Temconex® process which is a continuous extrusion using a mixture of metal powder and ceramic short fibre as feedstock. The Temconex® process was derived and further developed from the ConformTM process which uses metal rod rather than powder as feedstock. In the present paper the effect of the prechamber length on the mechanical properties was examined. As material Al99.7 powder with different volume fractions of milled carbon fibres was used. Distribution, orientation and geometry of the embedded fibres were examined using light microscopy. The mechanical properties were determined via tensile testing and resonance frequency analysis. An important increase of the Young’s modulus is observed because of the introduction of fibres. It can be rationalized based on Clyne’s Shear Lag model. Results show that an extension of the prechamber enhances the Young’s modulus and the elongation of fracture due to reduced fibre fracture and better fibre alignment.
Influence of Ti and Zn on Particle Incorporation of AlB2, B and B4C Particles in Aluminum Using the Stir Casting Process
Authors: Plötz Steven , Lohmüller Andreas , Singer Robert F.
Published: July 2017

The outstanding performance of many aluminum matrix composites (AMCs) regarding specific stiffness makes AMCs attractive materials for lightweight construction. Low density boride compounds promise both an increase in stiffness and decrease in composite density. Therefore for this study AlB2, B and B4C were chosen for composite manufacturing. The composites were fabricated with the stir casting process. To avoid gas entrapment during mixing and ensure nonporous composites, partial vacuum was adapted during particle feeding and stirring. Poor wettability of used particle material in contact with liquid aluminum hindered particle incorporation, but alloying elements such as titanium were shown to affect wettability and particle incorporation for B4C. Zn had no influence on wettability or reactivity and did not improve particle incorporation. In contrast to Zn, Ti improved adhesion and wettability, but particle incorporation was improved exclusively for B4C. Besides alloying Ti, the use of high-shear force mixers improved particle incorporation enabling uniform particle distribution. AMCs with up to 12 vol.% of B4C particles were produced via stir casting without alloying Ti.
Natural Fibre Reinforced Bioplastics - Innovative Semi-Finished Products for Series Production
Authors: Ouali Ahmed Amine , Rinberg Roman , Kroll Lothar , Nendel Wolfgang , Todorov Aleksandr , Cebulla Holger
Published: July 2017

The development of innovative bio-based composites with efficient manufacturing processes is the purpose of the current project C4 in the framework of the Excellence Cluster MERGE EXC 1075, funded by DFG (Deutsche Forschungsgemeinschaft). Efficiency in terms of mass-production, reproducibility and flexibility requires the performance of successive steps in the manufacture of semi-finished and final bio-based products. About bio-based materials, natural fibres composite (NFC) prepregs have been recently investigated as a potential cost-efficient semi-finished product. By means of continuous production processes, prepreg rolls can be manufactured with unidirectional natural fibres (flax) fabrics as reinforcement and thermoplastic biopolymers films as matrix. The used natural fibre non-crimp fabrics are made of high twisted yarns. For a better impregnation and higher stiffness properties, non-crimp fabrics with non-twisted yarns, which have been lastly developed by natural fibres suppliers, represent an appropriate solution. A second suitable option is the substitution of the biopolymer films, whose impermeability does not facilitate the release of humidity from the natural fibres while the impregnation, by produced low cost thermoplastic spunlace fabrics with a higher permeability and lower reachable surface weights. With these material developments and innovative process optimizations suitable to natural fibres, NFC prepreg properties tend to be improved. From prepregs to finished parts can be implemented by discontinuous processes, with compression molding and back-injection molding, or by continuous processes, with devices gathering several stages such as cutting, stacking, points welding, pre-heating and back injection molding. By stacking, a multi-axial orientation of prepregs can be performed in order to optimize the placement of reinforcing yarns according to the possible load path of future products. The mechanical properties profile of the combination of non-crimp natural fibres fabrics with thermoplastic films or thermoplastic spunlace fabrics has been here studied in detail with press-engineered samples and has confirmed the potential as an alternative to glass fibre-reinforced composite.
High-Performance Natural Fiber Composites Made from Technical Flax Textiles and Manufactured by Resin Transfer Molding
Authors: Pichler Stefan , Wuzella Günter , Hardt-Stremayr Thomas , Mahendran Arunjunai Raj , Lammer Herfried
Published: July 2017

In the present work it is shown that the resin transfer molding (RTM) is a beneficial technique to manufacture natural fibers into high-performance natural fiber composites. At first, three different types of weaves were produced by using low-twist flax yarns and standard-twisted flax yarns. Laminates based on the weaves and a petrochemical derived epoxy thermoset were fabricated by RTM process. For each laminate different numbers of plies (4, 5, 6, and 7) were used to achieve a broad range of vf (from 32 % up to 55 %) which are having a pore volume fraction, vp, as low as possible (min. 0.7 % - max. 2.7 %). For the laminates, flexural properties in warp and weft direction were determined (ISO 14125) and the effect of respective yarn type on flexural properties was investigated. The best properties were achieved for the laminate based on weave2 with vf = 55 % (strength=303 MPa, modulus=19.3 GPa). When laminates were tested again after half of the year the modulus and strength were reduced, but the strainincreased. The laminates were immersed into a water bath (ASTM D570) to test the influence of vf and vp on the water absorption behavior. The maximum water uptake (4-7 wt.-%) and the maximum thickness swelling (3-12 %) were observed for the samples with higher vf. Laminates based on weave1 were immersed again into the water bath to investigate the extent of deterioration of flexural properties with respect to water absorption at various time intervals. The laminates were tested immediately after removing from the water bath and after re-drying.
CATPUAL - An Innovative and High-Performance Hybrid Laminate with Carbon Fibre-Reinforced Thermoplastic Polyurethane
Authors: Zopp Camilo , Nestler Daisy , Tröltzsch Jürgen , Trautmann Maik , Nendel Sebastian , Wagner Guntram , Nendel Wolfgang , Kroll Lothar
Published: July 2017

In consideration of environmental aspects and limited availability of resources, the focus of automotive and aerospace industry lies on significant weight optimisations especially for moving loads. In this context, innovative lightweight materials as well as material combinations need to be developed. A considerable potential for lightweight structures can be found in fibre- or textile-reinforced semi-finished products. Due to their specific characteristics and extraordinary structural diversity, thermoset and thermoplastic matrix systems can be used. In particular, carbon fibres as reinforcing components combined with a thermoplastic matrix polymer are able to create new high-performance applications. Besides the significant lightweight characteristics of the fibre-plastic-composites, in some instances contrary requirements must be satisfied in many areas, such as strength and ductility. In this field, the combination of fibre-reinforced polymers with aluminium or titanium sheets creates unique composite materials, so called hybrid laminates, which fulfil the unusual expectations.The focus of the current study lies on the development of a new thermoplastic hybrid laminate named CATPUAL (CArbon fibre-reinforced Thermoplastic PolyUrethane/ALuminium laminate). The structure of the laminate is an alternating sequence of thin aluminium sheets (EN AW 6082-T4) and fibre-reinforced thermoplastic polyurethane (TPU). The individual layers are consolidated to each other by using a hot pressing process. First results showed that the impregnation capability of thermoplastic polyurethane surpasses any other commercially available hybrid laminates. Furthermore, the mechanical properties regarding bending strength and interlaminar shear strength are exceeding the state of the art drastically.
Rigidity and Damage Evolution of Long Fibre Reinforced Polypropylene Made by Direct Processing Route (LFT-D)
Authors: Weidenmann Kay André , Dietrich Stefan , Grigo Manfred , Elsner Peter
Published: July 2017

In order to reduce fuel consumption due to environmental aspects, weight of automotive components has to be reduced. Fibre reinforced polymers have high potential to contribute to this aim as they feature a high ratio of stiffness to weight. The direct processing route for long fibre reinforced polymers is a potential process for the net shape series production of automotive parts. To retain safety and comfort, the material properties of polymers processed in such a way have to be investi-gated thoroughly implementing a deeper understanding of elastic response and damage mechanisms. This work deals with glass fibre reinforced polypropylene manufactured by a direct LFT processing route (D-LFT). After introducing basic properties, studies to determine damage evolution are presented. In this regard, the decrease of stiffness with increasing strain was analyzed using tensile tests featuring loading-unloading cycles. The materials properties have been correlated to fibre orientation measurements from X-ray computed tomography. The stiffness decrease is compared to stiffness measurements carried out by ultrasonic phase spectroscopy (UPS) tests, carried out on juvenile, undamaged specimens. This method is used in this study for the first time to describe the elastic properties of long fibre reinforced thermoplastics.
Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process
Authors: Rupp Peter , Elsner Peter , Weidenmann Kay André
Published: July 2017

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.
Improved Adhesion Strength of Metal Textile Composites by Surface Texturing Using TIG Arc or CW Laser Process
Authors: Gültner Marén , Grosse Anna , Lohse Martin , Hertel Martin , Füssel Uwe , Droß Marcel , Lammers Marius , Hermsdorf Jörg
Published: July 2017

Within the framework of the bilateral CORNET projects MeTexCom and MeTexCom2, new approaches were developed and tested to improve the adhesion strength of metal textile composites, with a focus on the targeted roughening of aluminum surfaces and the development of new acoustically insulating nonwovens. The metal textile composites were produced by melting thermoplastic components of the textile composites without a separately applied adhesive.For improved adhesion strength between metal and textile, roughness was generated on the metal surface by means of a novel arc treatment by an anodic polarized TIG process or a cw (continuous wave) fiber laser process. On the one hand, the goal was to produce uniformly rough, untercut surface structures in micro-and nanodimension by means of a highly dynamic arcing process. On the other hand, a similar approach was pursued with the cw laser method by using a single-mode as well as a multi-mode laser.
Characterization of Hybrid Joining Techniques for FRP/Steel-Structures under Combined Mechanical and Thermal Loading
Authors: Hoepfner Marvin , Becker Torben , Hülsbusch Daniel , Walther Frank
Published: July 2017

In order to optimize the design of vibrating screening machines and realize significant weight reductions, the use of hybrid structures is gaining importance. In this context, the joining of FRP and steel and their interactions due to different material properties were investigated. Therefore, quasi-static tests with combined mechanical and thermal loads were carried out. To realize the simultaneous application of physical measurement techniques, e.g. optical and acoustic measurements, and thermal loads, short-wave infrared emitter technique was used instead of thermal chambers. Thus, the mechanical characteristics and acoustic emissions could be determined and assessed. The results show different structural mechanisms of hybrid joining at room and elevated temperatures. The characteristics of failure modes, shear stresses, strains and acoustic emissions could be correlated to determine the damage developments and mechanisms.
Influence of the Manufacturing Process (Comparison MuCell and Direct-LFT) of Foamed and Fiber Reinforced Polymer Sandwich Structures on the Fiber Length
Authors: Lohr Christoph , Menrath Andreas , Elsner Peter , Weidenmann Kay André
Published: July 2017

The automotive and aerospace industries ask for lightweight and cost effective materials, material combinations and structures for their products. To achieve these goals certain composite material groups have to be optimized with respect to their lightweight potential and production methods.Thermoplastic sandwich composites - which consist of a core structure (transferring the load) and two face-layers (absorbing tensile and compression loads occurring at bending) - suite the need of minimizing weight per area under bending loads. Reduction of process steps can be achieved by connecting the face layers and core in-situ via in mold assembly process using foam injection molding (FIM). FIM uses a single material system and – as within this work – physical blowing agents (PBA) for foaming. To increase the strength and stiffness of FIM parts, (long glass) fibers are in cooperated to create long fiber reinforced thermoplastic (LFT) materials.A commercially available version of the LFT-FIM process is the MuCell® process (Trexel, Inc.). LFT granulate (~ 11 mm length) is fed into the injection molding machine, melted and combined with nitrogen as PBA. To skip the needed compounding process step of the rod granules Fraunhofer ICT developed a Direct LFT-FIM process where polymer and continuous fibers are fed into a twin-screw extruder, melted and mixed with nitrogen. This single phase solution then is transferred to an injection unit.Within this work, these two foam injection molding processes will be compared concerning their achievable fiber length. For that purpose, (foamed) long fiber reinforced polypropylene (PP) blanks were manufactured using identical raw materials such as polymer, additives and glass fibers. The semi-finished product, starting material for the MuCell® process, were manufactured by EASICOMP GmbH using the same raw materials as with the D-LFT process. The different blanks – foamed and fiber reinforced PP (30 wt% and 40 wt %) – were manufactured using one injection unit for the MuCell® process and one for the D-LFT-FIM process. To compare the fiber length the same mold optimized to reduce fiber breakage was used in both processes.
Injection Molded Aluminum-Polymer-Composites - Integral Lightweight Structures with Potential
Authors: Frick Achim , Spadaro Marcel
Published: July 2017

Innovative lightweight structures realized by employing assembly injection molding bears high potential. Using assembly injection molding, complex shaped hybrid structures can be manufactured in a precise and fast processing step. Though, especially the interface quality of a hybrid joint is a crucial factor, which determines the overall quality of such lightweight structures. High bonding strength values were achieved between aluminum and multiple polymeric materials with double-lap joints manufactured by employing assembly injection molding. Thereby, the influence of aluminum surface pre-treatments as well as intrinsic adhesion modifications of the polymeric materials were investigated.
Polyelectrolyte Treatment of Cellulose Fibers for the Manufacture of Novel Bio-Hybrid Fiber Composites (Bio-HFC) for Lightweight Applications
Authors: Shamsuyeva Madina , Endres Hans Josef
Published: July 2017

In this study flax fabrics were treated with polyethylene imine (PEI) and afterwards, in combination with carbon fabrics, integrated into epoxy resin via vacuum infusion process. The influence of the 2 stacking sequences of the fabrics and 2 PEI concentrations were evaluated with regard to the mass fractions of the composite components and mechanical properties of the manufactured composites, namely, flexural and interlaminar shear properties. The results showed that the effect of the surface treatment is dependent on the stacking sequence. Namely, increase of the PEI concentration resulted in a corresponding increase of the mass fraction of the polymer matrix in the case of interchanging arrangement of flax and carbon fabrics. Further remarkable results showed that the same specimen provided the highest values of the supported maximum load after the surface treatment. Influence of the PEI treatment on the strength values with regard to the stacking sequence and polyelectrolyte concentration led to controversial results. Decrease of flexural modulus after the surface treatment was observed in the case of all samples.
Characterization of the Bonded Connection in Hybrid-Steel-GFRP-Laminates
Authors: Busch Arne Björn , Brandt Robert
Published: July 2017

Intrinsic hybrid laminates are well established since many years in aerospace engineering, e.g. Glass Laminate Aluminium Reinforced Epoxy (GLARE) is widely used as a substitute for aluminium sheets of the outer shell of modern aircrafts. The reduction of density and an increased stiffness by compounding glass fiber and aluminium makes GLARE advantageous. Driven by environmental protection acts and the need for lightweight design material compounds attract more awareness in the automotive engineering as well. Functional components like chassis springs are well predestined for the application of glass fiber reinforced plastics (GFRP). Therefore, an intrinsic hybrid made up by GFRP and a high strength steel has recently been developed and characterized. This investigation sets the focus on the interface between GFRP and steel. Double cantilever beam tests (mode I) and shear tests (mode II) are conducted in order to measure the energy release rate and the shear strength of the considered interface. A variety of surface treatments of steel layer has been characterized by this approach. The results show up that good adhesion can be achieved by silane and titanium dioxide primers, however, the variation within the data is significantly higher than for other surface treatment variants. Furthermore, the increase of the energy release rate by fiber bridging effects is considered as well and an approach for its quantitative description by a power law is presented.
Entrapment of Hard Particles into Cr(VI)-Free Conversion Layers of Electrodeposited Zinc Coatings to Improve Corrosion Resistance
Authors: Jehl Pierre , Halbedel Bernd , Lerp Marianne , Schmidt Udo , Teichert Gerd , Schlütter Frank
Published: July 2017

Due to the restriction of passive layers containing Cr6+ [1], which were characterized by excellent corrosion protection due to their self-healing effect for scratches on metal surfaces, current corrosion protection systems consist of chromium (III) -containing thick layer passivation. Due to their lower hardness, current corrosion protection systems are susceptible to mechanical stress. This is particularly critical at barrel plating of screws, rivets etc. where the manufacturing process leads to damages of the corrosion protection layer and consequently to reduced corrosion resistance.To counter this problem, we point out one approach to install hard particles into the passivation layer. The entrapment of the hard particles into the passivation is detected by Glow Discharge Optical Emission Spectrometry. Comparative investigations in the corrosion chamber prove the improvement of the corrosion protection of steel parts with passivation layers containing hard particles.
Wetting Behavior of Carbon Fibers: Influence of Surface Activation and Sizing Type
Authors: Laukmanis Eva , Brück Bastian , Bauer Matthias , Moosburger-Will Judith , Horn Siegfried R.
Published: July 2017

To investigate the wetting behavior of unsized carbon fibers with a sizing dispersion and the wettability of sized fibers with the liquid polymeric resin, contact angle measurements by capillary rise experiments are performed by tensiometry. First, the sizing behavior of fibers with different degrees of surface activation is analyzed. Increasing activation levels result in increasing oxygen surface concentrations and accordingly increasing polar components of the surface energies. These conditions result in a better wettability of the higher activated fibers. Secondly, the influence of the type of sizing dispersion is addressed by using two water-based epoxy sizing dispersions, i.e. a standard epoxy sizing and an advanced functional epoxy sizing with high reactivity. Using the functional sizing the wettability is further improved. Finally, the influence of the sizing on the wettability of the carbon fibers by the matrix polymer during resin infiltration is investigated using the differently sized fibers and a liquid epoxy resin. Carbon fibers with functional sizing show improved wettability by the resin compared to fibers with standard sizing. The results show that the wetting behavior of carbon fibers with respect to sizing and polymer matrix can be controlled by a suitable choice of surface activation of the fibers and reactivity of the polymeric sizing dispersion.
Torque-Fiber-Winding (TFW)-Procedure: Manufacturing of Textile-Based Unidirectional Prepreg for Raw Material and Material Development of Carbon Fibre Reinforced Thermoplastics
Authors: Kolonko Angelika , Helbig Frank , Tröltzsch Jürgen , Nestler Daisy , Kroll Lothar
Published: July 2017

There is the need to determine the process capability of available and novel carbon fibre (CF) roving with minimal material and reproducible procedures in the field of research and development of continuous fibre reinforced composites and structural components, as well as to identify the power delivery in thermoplastic laminate constructions.
The innovative TFW procedure with the appropriate system technology allows the production of piece size variable unidirectional (UD) prepreg in a continuous sequential process of spiral winding. A flexible surface design, resulting in the partial fixation of a single highly spread CF roving on fine nonwoven fabric. By defined accumulating of composite components, the fibre volume content (FVC) is adjustable and correspond to the level of spreading and to the grammage of nonwoven fabric. Minimum single layer thickness promote compound homogeneity and thereby allow the generation of greatest possible degrees of freedom in load-oriented structural design of CF-reinforced thermoplastic lightweight products in the laboratory staff.