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Owing to its remarkable properties, multiwalled carbon nanotubes (MWCNTs) are attracting the interest for realization of sensors. The potential of MWCNTs for high temperature sensing applications was investigated by integration within reinforced aluminium oxide ceramic composite. MWCNTs up to 2 wt% were mixed with reinforced aluminum oxide ceramic composite using solution mixing method to ensure good homogeneilty of the oxide ceramic composite powders. Specimens were realized using ceramic injection moulding process (CIM) followed by debinding and sintering procedures. The topography of specimens were examined using atomic force microscopy (AFM). Electrical measurements were also carried out. The results show good demouldability at high MWCNTs concentration and homogenous distribution of the MWCNTs within the oxide ceramic matrix. AFM images illustrate the reduction of surface roughness by increasing the MWCNTs content which demonstrates the role of MWCNTs to improve the fracture resistance of the oxide ceramic matrix composite. As well, the electrical resistance of the feedstocks were reduced sharply. After sintering process, the resistance range drops enormously from M Ω to reach 12.1 Ω at low MWCNTs content; which make them suitable to be as electrode with high temperature capability. The electrical resistance temperature dependency shows a negative temperature coefficient behaviour with negligible resistance change.

For the production of C/C-SiC brake discs via the liquid silicon infiltration method (LSI), the hot pressing process is the state of art technique for the moulding of the CFRP composites. This technique consists of several manual steps which increase production cost. The overall cost can be reduced by implementing injection moulding process. In this paper the influence of the moulding process (hot pressing, injection moulding) on the properties of semi-finished and final products during the production of short-fibre-reinforced C/C-SiC composites by means of the LSI process are examined. The starting polymer is chemically characterised. Carbon-fibre-reinforced plastic (CFRP) composites are fabricated by hot pressing, as well as injection moulding process. The CFRP composites are converted into porous C/C composites by pyrolysis. Liquid silicon is infiltrated to form dense C/C-SiC composites, which are further investigated during the course of this paper. Significant differences in properties of the composites are discussed.

Innovative materials for substituting metals are required to reduce the mass of moving components. This decreases the CO2 emissions of overall systems. A thermoset sandwich for high mechanical properties and thermal insulation is presented in this paper. It has an innovative 3D continuous reinforced core, which allows the optimisation of the substance exploitation by wide-ranging possibilities of fibre orientation. This was demonstrated with three sandwich variants. The reference had no core reinforcement and the other two were reinforced with different spacer fabrics. The process chain for the manufacturing consists of Structural Reaction Injection Moulding (SRIM) and Vacuum Assisted Resin Transfer Moulding (VARTM). Significant increases in absolute as well as specific characteristic values were demonstrated by the reinforcement in a compression and bending test. It was also shown that quasi-static characteristic values under fatigue loading are maintained to a greater extent with the core reinforcement. The sandwich material was applied as a floor assembly for a snow groomer. The design was tailor-made for the mechanical, thermal and acoustic requirements. This proved the transferability of the process chain for manufacturing samples to the production of large-volume components with complex geometry.

Ceramic-matrix composites (CMC) made of carbon and silicon carbide dual matrix reinforced with carbon fibres (C/C-SiC) have exceptional heat, thermal shock, creep, and wear resistance, while also having little density and high strength. In comparison to monolithic ceramics, CMC possess ductility and damage tolerance, which opens this material for severe applications. Starting in space applications, this material is today well established in friction applications, where lightweight high-performance brakes securely decelerate e.g. luxury cars or elevators. The high production costs still limit the broad application like as brake discs in standard passenger cars, although less weight, better performance and longer lifetime. The industrial used production process is the liquid silicon infiltration (LSI) with it three steps: green body shaping, pyrolysis and silicon infiltration. In this work, the shaping process of the carbon fibre reinforced plastic (CFRP) green body, is done by thermoset injection moulding. The application of plastic production processes like compounding and injection moulding in the liquid silicon infiltration process route, enables large-scale manufacturing. However, the screws and high shear forces inside the plastic processing machines significantly shorten the fibres. This paper describes the pros and cons of thermoset injection moulding in the LSI route, as well as the development and effect of different reinforcement types in dependence of their fibre length, since several energy dissipation mechanisms bases on a minimum length of reinforcement fibres in CMC. Various raw materials like short and chopped fibres with different length, rovings, and different approaches to receive longer fibres and their outcomes are presented. The mechanical properties show promising values and the micrographs display the infiltration status and crack development inside the specimen.

Ceramic materials are suitable for use in the high temperature range. Oxide ceramics, in particular, have a high potential for long-term applications under thermal cycling and oxidising atmosphere. However, monolithic oxide ceramics are unsuitable for use in high-temperature technical applications because of their brittleness. Thin-walled, oxidation resistant, and high-temperature resistant materials can be developed by reinforcing oxide ceramics with ceramic fibres such as alumina fibres. The increase of the mechanical stability of the composites in comparison to the non-fibre reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fibre under mechanical stress or deformation. Components made of fibre-reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. Therefore, the manufacturing should be improved. The ceramic injection moulding (CIM) process is established in the production of monolithic oxide ceramics. This process is characterised by its excellent automation capability. In order to realise large scale production, the CIM-process should be transferred to the production of fibre-reinforced oxide ceramics. The CIM-process enables the production of complicated component shapes and contours without the need for complex mechanical post-treatment. This means that components with complex geometries can be manufactured in large quantities.To investigate the suitability of the injection moulding process for the production of OCMCs, two different feedstocks and alumina fibres (Nextel 610) were compounded in a laboratory-scale compounder. The fibre volume fractions were varied. In a laboratory-scale injection moulding device, microbending specimens were produced from the compounds obtained in this way. To characterise the test specimens, microstructure examinations and mechanical-static tests were done. It is shown that the injection moulding process is suitable for the production of fibre-reinforced oxide ceramics. The investigations show that the feedstocks used have potential for further research work and for future applications as material components for high-temperature applications in oxidising atmospheres.

Sandwich structures consisting of fibre-reinforced plastic (FRP) facings and core are ideally suited as substitution materials for reducing component masses. The endless fibre reinforcement has the greatest performance potential. Both thermoset and thermoplastics are already being processed into endless fibre-reinforced sandwich facings according to the state of the art. The 3D endless fibre reinforcement of cores is a current research topic. This paper describes the development of a hybrid sandwich consisting of thermoplastic composite facings and an innovative core composite. This is made of polyurethane (PUR) rigid or flexible foam, which is reinforced with spacer fabric. The sandwich manufacturing in Reaction Injection Moulding (RIM) includes the original forming of the core and the simultaneous bonding of the facings. This efficient process offers the potential for the production of such complex structures in medium or large series. The sandwich structures and their individual components were characterised in the standardised compression and bending test. The lightweight potential of spacer fabric reinforcement is demonstrated by comparing the specific mechanical properties of sandwich structures with and without core reinforcement. In comparison to reinforced and unreinforced foams, the effect of sandwich design is also shown.

The production of C/C-SiC composites comprises a three-stage process: forming (CFRP-composite), pyrolysis (C/C-composite) and liquid silicon infiltration (C/C-SiC). A new promising approach for the manufacturing of CFRP intermediate composites is the injection moulding of customised granulates (novolac resin, hardener, processing additives and short carbon fibre) produced by compounding technique. To date, a direct dosing of short carbon fibre into the compounder was technically not realisable due to fibre separation and electrostatic charging in the hopper. A possible substitute solution has been the direct feeding of a carbon fibre bundle from a roving into the compounder. However, this is associated with a severe damage of the fibres and an inaccurate adjustment of the fibres content. In the present article, new chopped carbon fibres provided with an adapted sizing to be directly dosed into the compounder are used. The fibres possess a predefined length of 3 and 6 mm and their content amounts to 50 and 58 wt.%. The influence of the initial fibre length and fibre content on the physical and mechanical properties of the resulting CFRP-, C/C-and C/C-SiC-composites is presented and discussed. In addition, the impact of fibre feeding procedure at the compounding stage on the microstructure is considered

Hybrid laminates consisting of fibre-reinforced thermoplastic films and metallic thin sheets are successively replacing thermoset based systems due to their obvious advantages of higher formability and aptitude for mass production. In order to monitor the material under operating conditions, hybrid laminates need to be equipped with smart sensor units. Artifact-free integration of commercial strain gauges into hybrid laminates is almost impossible. Therefore, a new thin film strain sensor based on a PVD sputtering process was developed.The aim of this work was to evaluate the influence of the layer thickness as well as the elevated temperature during the sputtering process on the electrical performance of Ni-C strain sensors. The Ni-C films with different layer thickness and different sputtering temperatures manufactured by means of a magnetron sputtering process were investigated for the sheet resistance and the change of temperature coefficients of resistance. In addition, Raman spectroscopy was utilized to investigate the phase development with regard to different sputtering temperatures. It can be seen that the gauge factor gets doubled while optimizing the layer thickness. When the sputtering temperature was increased, the graphitic phase formation was preferred and the impurities were reduced. These results are discussed in this paper and appropriate solution concepts are provided.

Carbon fibre reinforced carbon and silicon carbide dual matrix composites are a commercially produced using the liquid silicon infiltration (LSI) process. In comparison to the state of the art LSI process, the first production step—the shaping of the carbon fibre reinforced plastic green body—is realised through thermoset injection moulding. Using this method, the complete process can be automated. Simultaneously, the injection moulding technology allows complex geometries with near net shape in short cycle times of about two to five minutes. Thereby, this large-scale process offers a wide range of shot weights from a few mg up to 100 kg, also in multi-component technology. Also, several manufacturing steps can be omitted. This improves the reproducibility, and working in closed environments improves the employees’ health protection. Further process steps, like pyrolysis and silicon infiltration follow the state of the art. Although, this promising approach significantly shortens the fibres, the defined plastic processing is highly reproducible and generates similar mechanical properties like manual processes, due to the better fibre/matrix interaction in the plastic composite. In addition, continuous fibre preforms can be inserted to fulfil higher requirements.

Sandwich structures, consisting of a short glass fibre–reinforced polypropylene film as skin layer and chemically blown polypropylene as the core material, were produced via injection moulding. The skin layers of the sandwich structures, which contain polypropylene as well as 30 wt% and 50 wt% of glass fibres namely polypropylene–glass fibres 30 and polypropylene–glass fibres 50 respectively, were produced by film extrusion using a coat hanger die. The properties of the films were investigated by dynamic mechanical analysis. Furthermore, the influence of different glass fibre contents in the skin layers and chemical blowing agent contents in the core material of sandwich structures was studied to compare them with the compact polypropylene and the polypropylene foams. The sandwich structures were characterized with regard to density, microstructure, weight reduction, surface roughness and bending properties. In general, distinctive reinforcement effect was achieved by use of the short glass fibre with the strong influence of processing direction of the film. For the sandwich structures, it was found that a good adhesion between the skin layers and the core material can be achieved during injection moulding. The microstructure and the bending properties of the sandwich structures depend on the glass fibre–reinforced film and the chemically blown core. It was found that the use of the skin layers led to lower cell intensity in the foam core. Nevertheless, a high modulus and strength to weight ratio could be accomplished by a high stiffness of the glass fibre–reinforced film and a low density of the chemically blown core. Additionally, it was found that the surface roughness of the films could be reduced due to processing in injection moulding.

Ceramic-matrix composites (CMC) made of carbon and silicon carbide dual matrix reinforced with carbon fibres (C/C-SiC) offer some technical advantages like exceptional heat, thermal shock, creep, wear resistance, and no fine dust load, while also having low density and high strength. Showing these excellent properties, this material is well established in high-performance brake applications, e. g. in luxury cars or elevators. However, the industrial production process of this material is still not applicable for mass production. Due to high production costs, a broad application of this material in products like brake discs in standard passenger cars is not feasible at the moment. To exploit the technical and economic potentials and realise a broader market penetration, the thermosetting injection moulding process presented in this paper is explored as a shaping process of the carbon fibre reinforced plastic (CFRP) moulded body. In this way, a fully automated and high-volume production can be realised. From the economic point of view, the option of introducing a large-scale manufacturing process bears the potential of achieving considerable cost improvements. To assess and demonstrate the potentials of C/C-SiC shaped by thermosetting injection moulding and their chances for market penetration, a holistic technical-economic evaluation is necessary. The paper demonstrates a methodology for an integrated evaluation from a technical as well as an economic view and applies it to C/C-SiC and thermosetting injection moulding. By revealing the potentials, it contributes to the broad application of products made of C/C-SiC in the future.

Hybrid laminates consisting of fiber-reinforced thermoplastic films and metallic thin sheets are successively replacing thermoset-based systems due to their obvious advantages of higher formability and the aptitude for mass production. In order to monitor the material under operating condition, hybrid laminates need to be equipped with smart sensor units. Therefore, the aim of the present work is to evaluate the temperature stability of the Ni-C thin film strain gauge sensors. The analyses of the deposited Ni-C films manufactured by means of a magnetron sputtering process were carried out by means of Raman spectroscopy and X-ray diffraction to investigate the phase development after a heat treatment at different temperatures and holding times. In addition, the four-terminal sensing was utilized to study the change of temperature coefficients of resistance after a single annealing treatment.

In an effort to reduce the mass of components, sandwich design has become well established above all in the aerospace and the vehicle construction. In these structures, facings and cores made of ve...

Lightweight construction combines various materials to create resource efficient components. Thermoplastics (TPs) combined with polyurethane (PUR) foams are increasingly used to create hybrid composites. Optimizing the energy efficiency is one of the main issues in the development of production processes of components. Reducing the number of process steps offers great potential in this respect. PUR foam develops a strong adhesive bond with most materials. This is used for the manufacturing of hybrid composite components by filling complex cavities with PUR foam simultaneously bonded with other TP polymer components. This way, one process step for joining is saved. The interfaces in this composite structures are critical points of the failure. A huge variety of TP is used for the production of hybrid composite components and PUR foam develops varying bonding strengths with all of them. Selecting the suitable TPs for a durable bonding with PUR foam in the desired production process necessarily requires information about the respective specific adhesion. In this investigation, different TPs were processed with PUR foams in order to manufacture sandwich composites. The TP facings are produced in the injection moulding process. Subsequently, the facings are combined with the foam core during reaction injection moulding. The wetting behaviour was examined using the contact angle measurement and the mechanical strength of the interface in the sandwich composite was determined using a tensile test. A precise order of the selected TPs concerning their specific adhesion to PUR foams was achieved with these investigative methods.

Carbon fibre reinforced carbon composites (C/C) are characterised by their excellent thermal, chemical and mechanical properties. The intrinsic porosity and fibre reinforcement grant them an excellent damage tolerance. The production of complex structures is time consuming and very expensive. An innovative approach to this topic is the integration of simple geometric ceramic composite materials within complex polymer structures. The motivation of this contribution is to investigate the influence of hexamethylenetetramine as hardener (hardener content: 4, 8, 12 and 16 %) and curing parameters (tempered and non-tempered) on the microstructure and mechanical properties of the porous C/C composites. During the course of this contribution, selected carbon fibre reinforced polymer (CFRP) composites with different porosities were produced while adjusting the resin or hardening agent-ratio, as well as the processing parameters. Subsequent to the curing of the CFRP samples, porous C/C composites were produced by means of a pyrolysis process. The final part of the contribution is comprised of the microstructural analysis by light microscopy and the explanation of the flexural strengths, by utilising a “three-point-bending test”.

Continuous fibre reinforcements in thermoplastic composites require an enhanced adhesion to the matrix component, in order to effectively divert external forces from the matrix. Therefore different silanes as adhesion promoters are used as a part of the sizing. They operate as a connector to the matrix component. These silanes affect the sliding properties of the sizing during the production of the glass filaments in a negative way, in which case the proportion of the adhesion promoter in the sizing must be kept at a low level in order to maintain the processing speed in the textile production process. With the immersion bath method, it was examined whether the treatment of the surface of textile fabric after the textile production process with a silane-containing aqueous solution could solve these problems. Different silane concentrations and solvents were considered. After drying the textiles were processed during a two-step pressing process directly into a multi-layer organic sheet with a textile-based polypropylene matrix. The successful layering of the adhesion promoter on the glass fibre surface was verified by Fourier transform infrared (FTIR) spectroscopy. With thermogravimetric analysis (TGA), the thermal resistance of the adhesion-promoting layer for the subsequent pressing process could be shown. In order to examine the influence of the layer on the fibre/matrix adhesion within the composites, the Young’s modulus and flexural modulus of the composite panels were determined. Impact experiments were made to measure the required penetration energy and the energy absorption capacity of the composite panels. An optimum for the amount of adhesion promoter could be found. Exceeding the optimum amount of adhesion promoter in the solution led to a decrease in the mechanical properties of the composite.

Hybrid textile-based composites possess an enormous potential for energy and resource efficient large-scale production, with freedom in and high specific mechanical properties. This paper covers the connection of available and established production processes for textiles in a differential process chain for the manufacturing of complex shaped and elastic sandwich components. The technology enables both stiffness and comfort through elasticity.OLU-Preg®-organic sheets, polyurethane foam cores and 3D-spacer fabrics form the targeted properties of demonstrator models. This article refers to the demonstrator part “bucket seat”. To show the benefit of complex composite material, the lightweight and mechanical properties of the sandwich structures are tested in several variations of core and comfort shapes. Absolute and specific improvements of performance are shown in static and dynamic examinations. An Analysis of coupling effects, deformation and failure behavior of the multi-material design (MMD) complete the scientific approach of the structure-property relationships of hybrid composites.

Sliding electrical contacts are traditionally produced by conventional compacting technologies. Employing the powder injection moulding process (PIM) as a new manufacturing method can offer several advantages such as the fabrication of complex net-shaped parts, cost-effectiveness and high volume productions. The PIM process route consists of the following steps: powder processing, compounding, injection molding, debinding and sintering. A two-stage process consisting of solvent debinding and thermal debinding is often used to remove the moulding binder. In the present paper, the suitability of the powder metallurgical processes: mechanical alloying and powder mixing for the preparation of bronze-graphite powder mixtures for the compounding and injection moulding of sliding contacts is discussed. The use of a suitable binder is of central importance for the preparation of injection-moldable feedstocks. For this purpose, two commercial ready-to-use binder systems were utilized and evaluated. The essential challenge of the process route is to optimize all parameters of the subprocesses to achieve a damage-free debinding and sintering of the injection-moulded parts. First results on the influence of the graphite content, the binder fraction, the debinding and sintering parameters are presented and discussed.

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.

For the development of an efficient and economic recycling process of carbon fibers (CF) still many technological challenges have to be mastered. One of them is the removal of all extraneous natural and synthetic fibres, e.g. polyester sewing threads. The objective of the research was to develop an in-line process for the removal of those extraneous fibres, which result from mechanical processes such as tearing. A promising approach for the removal of extraneous fibres from cut-off carbon-fibre material (CF) has been identified, getting recycled carbon fibres (rCF). For that purpose, the use of modern laser technologies is particularly promising. However, the focus was not the development of new laser systems, but the adaptation of existing technologies and their integration into textile processing steps for carbon fibre recycling. In addition to the removal of the extraneous fibres, the degree of CF losses and quality degradation due to fibre damage have been analysed and compared with optimum fibre characteristics. The separation has been experimented and corresponding laser parameters have been defined. Finally, the obtained carbon-fibre material has been tested with regard to its processability in textile manufacturing processes (dry non-woven fabric production) up to carbon fibre reinforced plastics (CFRP). For the evaluation of the material for potential applications, test plates from irradiated and non-irradiated material have been used. The performed tensile and flexural tests have proved that the irradiated material has similar properties compared to the non-exposed one.

Sandwich composite materials are established in the industry. Polyurethane foam reinforced with spacer fabric represents an innovative solution for a core in this field. It is manufactured in the Structural Reaction Injection Moulding (SRIM). This paper describes new investigations that provide the base for component and process design when using this Interpenetrating Phase Composite (IPC). Filling studies were carried out for this purpose in three moulding tools with different cavities with and without spacer fabric. It is shown that the PUR foam expansion and the foam bulk density are clearly influenced by the sprue type, cavity design and spacer fabric. Simulations are necessary to investigate all process-structure-property relationships in detail and to enable a user-friendly and efficient design of material and process. Adequate mathematical models to simulate the transport of mass, heat and momentum in the SRIM are presented in this paper. The resistance to the expansion process caused by the porous structures in the domain were taken into account. The transport of momentum in the mould is described with the Navier–Stokes-Brinkman equations which in the limit of the permeability tensor reduces to the Navier–Stokes equation. The model equations are solved numerically and the results show reasonable agreement with the experimental data.

Thermoplastic-based so-called Fibre Metal Laminates, consisting of fibre reinforced plastics foils and metal sheets in an alternating structure, can be efficiently produced via a continuous film stacking process of a Fibre-Foil-Tape Unit (FFTU) and subsequently thermoforming process. These materials combine the advantages of the individual material groups and offer a great potential for lightweight structures. A construction was tested with bending and torsion tests and compared to steels. By connecting the FFTU-technology with the thermoforming process, the economical aspect can be increased considerably. The weight was reduced up to 29%, despite increasing the thickness of the hybrid laminate.

The research and development of new materials such as particle-reinforced aluminum matrix composites (AMCs) will only result in a successful innovation if these materials show significant advantages not only from a technological, but also from an economic point of view. Against this background, in the Collaborative Research Center SFB 692, the concept of an integrated technology, user, and market analysis and forecast has been developed as a means for assessing the technological and commercial potential of new materials in early life cycle stages. After briefly describing this concept, it is applied to AMCs and the potential field of manufacturing aircraft components. Results show not only technological advances, but also considerable economic potential—the latter one primarily resulting from the possible weight reduction being enabled by the increased yield strength of the new material.

This article focuses on the development of phenolic resin moulding materials for the production of new carbon fibre-reinforced ceramic composite materials based on C/C-SiC by utilising the LSI (liquid silicon infiltration) production method. The production of these moulding materials is being accomplished by combining phenolic resin and carbon fibres with the addition of a few selected parts of processing aids, during which the influence of the used lubricants on the processability of the moulding materials is examined. The starting materials, microstructures and mechanical properties of the materials were characterised at every step of the entire process (CFRP and C/C composites) as well as the end of the whole production (C/C-SiC composites). During this investigation a link between the portions of the lubricant used, the forming of the porosity and the impact on the mechanical properties was discovered. In regards to the optimisation of the process the involved parties were able to determine an optimal lubricant ratio.

SiC/SiC ceramics consist of silicon carbide fibres embedded in a silicon carbide matrix. As an alternative to classic CVI and PIP routes, Liquid Silicon Infiltration (LSI) was chosen as a technique with short process times to obtain composites with low porosity. Silicon carbide composites show good thermal shock resistance, a low coefficient of thermal expansion and excellent physical and chemical stability at elevated temperatures and are therefore regarded as promising candidates for various applications in jet engines and in power engineering. To build up the matrix, different phenolic resin based carbon precursors were infiltrated in fibre preforms and thermally cured, pyrolysed and siliconized. The aim is to obtain a high carbon yield during pyrolysis and to control the pore morphology in a way that the following liquid silicon infiltration leads to a complete reaction of the carbon matrix with silicon to SiC. The siliconization behaviour and conversion into SiC in dependence of pore morphology and chosen precursor is analysed.At the same time a functional fibre coating has to be developed which protects the fibres from liquid silicon and simultaneously provides a weak fibre matrix bonding. A LPCVD-SiNx fibre coating has been chosen and is investigated in fibre composites especially in terms of protection and reactivity in different atmospheres during pyrolysis and siliconization.

Fibre-reinforced ceramic composite materials offer excellent thermal, mechanical and chemical properties. Due to their intrinsic fibre structure and porosity, they offer a great damage tolerance. Therefore, they provide superb attenuation characteristics, as do polymer composites. The current compound systems consisting of ceramic components feature a rather low capacity for energy absorption in relation to their weight; this is a fact in dire need of a fundamental change. In regards to the development of new hybrid ceramic/polymer material compounds basic research of the material design and binding behaviour of the different components is necessary. The advantage of this development allows for a selective implementation of positive characteristics of one component in an integrated compound-system. This opens up completely new possible are-as of application, such as wear and tear resistant and chemically inert, energy absorbing elements for the construction of reactors or areas of medical technology. During the investigation, a few selected fibre-reinforced ceramic composite materials with a specific porosity were produced, while adjusting the amount of resin/hardening agent used, as well as modifying other parameters. This was followed by tests regarding the wetting with a polyurethane component. The characterisation and analysis of the hybrid compounds on a microscopic scale is achieved by means of optical microscopic examinations. The characterisation of the mechanical attenuation characteristics on the other hand is realised by means of DM(T)A. The flexural strength is determined by utilising a “three-point-bending test”.

Sandwich structures consist of one light core layer and two top layers, which form the load-bearing structure. These layers have to be stiff and strong and have to protect the structure against indentations. The main task of the core layer is to keep the top layers in place and to generate a high shear stiffness. In order to obtain the required space between the top layers, the core layer has to have a high specific volume. Different sandwich materials with aluminium or steel top layers and cores of aluminium combs, corrugated aluminium sheets or aluminium foams are already known. In order to obtain better properties in terms of strength fibre-reinforced plastics (FRP) are utilised as top layers; this is the focus of numerous of the current research studies. The sole use of these materials leads to negative effects regarding the damage and impact behaviour. New top layers with high strength and high stiffness characteristics as well as good damage tolerances are to be expected by utilising metal layers in combination with endless fibre-reinforced plastics, so called hybrid laminates. These hybrid laminates combine the positive properties of metals (e.g. ductility) and fibre-reinforced plastics (e.g. tensile strength). The focus of this investigation lies on the production and characterisation of sandwich structures with aluminium foam core layers and hybrid laminate top layers. The foam cores consist of closed pore aluminium foams produced by utilising ingot and powder metallurgical techniques. The top layers consist of glass fibre-reinforced thermoplastics and aluminium layers. The production of the sandwich materials is realised by means of thermal pressing.

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.

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.

Hybrid laminates with thermoplastic matrices offer clear advantages over laminates based on thermosetting resins. These include the formability, recyclability as well as the suitability for mass production, to name a few. The inline integration of smart systems like sensors and actuators in the hybrid laminates during the hot-pressing process is one of the long-term objectives of the Federal Cluster of Excellence MERGE. This work aims to deposit Ni-C thin films by dc magnetron sputtering on polyimide substrates for the application as strain sensors in hybrid laminates. During the first step hybrid laminates containing different polyimide foils were prepared by hot-pressing, this was followed by the mechanical testing and selection of the most suitable polyimide substrate for the Ni-C thin film deposition. The second part consisted of depositing Ni-C thin films by means of dc magnetron sputtering and utilising different Ni-C plug targets. The films were characterised regarding their growth rate, composition, structure and temperature coefficient of electrical resistance.

The increasing implementation of fibre-reinforced plastics (FRP) leads to a broad utilization of metal/FRP joints. The examination of adhesively bonded metal/FRP joints is focusing on the maximum joint strength and the surface pretreatment used to promote it. A deeper understanding of the mechanisms behind the correlation is lacking. Along with the chemical condition of the surface (free chemical bonds, polarity, etc.) the surface morphology plays an important role. This study addresses the connection between the surface morphology and joint strength. The investigation of the surface morphology of the metallic joining area and the fractured surface of both joining partners by means of imaging and tactile methods and the results are presented.

Uncoated SiC fibres in SiC/SiC composites manufactured by the liquid-silicon infiltration (LSI) process show a strong degradation as a result of silicon attack. The goal of this research is the development of a SiNx-based fibre coating, which acts as a barrier against the liquid silicon. The coating is applied by means of low-pressure chemical vapour deposition (LPCVD) utilising the gaseous precursors silane (SiH4) and ammonia (NH3) on a commercial SiC multifilament yarn. The result is an amorphous fibre coating with an increasing coating thickness and a variable chemical composition from the middle of the yarn to the edges. The coated fibres exhibit a reduced characteristic Weibull strength in comparison to the uncoated fibres. In order to examine the stability of the films, the coated fibres undergo a heat treatment at 1450 °C in different environments (vacuum, argon and nitrogen). In all environments, the amorphous SiNxcoatings crystallise to the trigonal Si3N4. Depending on the coating thickness cracks and defects develop. However, the best results and the lowest amount of damaging occurs during the treatment in nitrogen.

In gemeinsamer Kooperation der Professuren Verbundwerkstoffe (Prof. G. Wagner), Strukturleichtbau und Kunststoffverarbeitung (Prof. L. Kroll) sowie Polymerchemie (Prof. S. Spange) der Technischen Universitat Chemnitz wurde ein grosserientaugliches Formgebungsverfahren zur Herstellung faserverstarkter C/C-SiC-Verbunde entwickelt. Das Verfahren wird die Produktionskosten erheblich senken.

Products made of polyurethane foam are manufactured by the chemical reaction of various low-viscosity raw materials and additives. The diversity of different formulations to meet the requirements of the market makes the characterization of their processing and flow properties important for a simple and error-free production. The modeling and simulation of such processes are equally of great importance. This provides additional findings without the expense of real tests and makes it easier to design components. The work described in this paper was carried out against this background. An experimental setup using a rheometer was developed to determine the flow and curing properties of reacting polyurethane foam reproducibly with comparable expansion conditions to industrial processes. The experiment was mathematically modelled to investigate the rheology of reacting polyurethane foams. The mathematical framework consists of coupled, non-linear, partial differential equations for the dynamics and the heat transfer processes in the system. These are solved numerically in 3D using finite volume techniques under adequate physical conditions. The accuracy of two viscosity laws according to the state of the art and their novel combination were investigated in this context. The proposed viscosity model of this study provides accurate results compared to the experiment.

In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstarkter polymerer Komponenten miteinander kombiniert. Vorteile der thermoplastischen Kunststoffkomponente, wie z. B. Umformbarkeit und Recyclingfahigkeit sowie Grosserientauglichkeit, bieten einen herausragenden Vorteil gegenuber duroplastischen Matrices. Zur Herstellung der Hybridlaminate werden in einem ersten Schritt Endlosfasern und Thermoplastfolien zu unidirektional faserverstarkten Tapes vorkonsolidiert. Anschliesend werden diese belastungsgerecht mit der metallischen Komponente verpresst, wobei das Interface zwischen faserverstarktem Thermoplast und der metallischen Folie eine entscheidende Rolle spielt. Im vorliegenden Beitrag werden Hybridlaminate mit kohlenstofffaserverstarktem Polyamid (CF-PA6) als Kernschichten und glasfaserverstarktem Polyamid (GF-PA6) als Zwischenschicht zur metallischen Komponente untersucht. Bei den Laminaten kommt ein 2/1- sowie 3/2-Aufbau mit zwei bzw. drei Metalllagen sowie einer bzw. zwei Lagen faserverstarkten Kunststoffes zum Einsatz. Als metallische Folie werden die Aluminiumlegierung EN AW-6082 und die Titanlegierung Ti3Al2,5V (Grade 9) verwendet. Die Laminatherstellung, die Entwicklung und die Einstellung des Interfaces sowie die Evaluierung der mechanischen Eigenschaften werden im Beitrag diskutiert. Hybrid laminates combine the positive properties of the metal and fibre reinforced plastic (FRP) components. Advantages of the FRP, like formability, recyclability as well as suitability for mass production, provide an outstanding advantage over thermosetting matrices. For the production of the hybrid laminates, at first continuous fibers and thermoplastic films are pre-consolidated to fibre-reinforced unidirectional tapes. Subsequently, these are pressed together with the metal component in a loadcapable optimized arrangement. Thereby the interface between the FRP and the metal foils is of crucial importance. This paper focuses on hybrid laminates with carbon-fiber reinforced polyamide (CF-PA6) functioning as core layers and glass-fiber reinforced polyamide (GF-PA6) as intermediate layers between the centre and metal component. Laminates in 2/1 and 3/2 structure with two respectively three metal layers and one respectively two FRP layers are examined. For the metal foil, the aluminium alloy EN AW-6082 and the titanium alloy Ti3Al2.5V (Grade 9) are used. The production of these laminates, development and adjustment of the interface and the evaluation of mechanical properties are investigated in this article.

Effizienter Leichtbau erfordert intelligente Werkstoffe, die vielseitige Funktionen erfullen. Ein Losungsansatz besteht darin, Kohlenstofffasergewebe galvanisch zu metallisieren, um funktionelle kohlenstofffaserverstarkte Kunststoffe (CFK) herzustellen. Es resultiert eine rissfreie, homogene Nickelschicht auf der Gewebeoberflache. Durch eine geeignete Wahl der Beschichtungsparameter wird daruber hinaus jede einzelne Faser des gesamten Gewebes gleichmasig metallisiert und eine Anwendung in funktionellen kohlenstofffaserverstarkten Kunststoffen fur Leichtbauwasserstoffspeicher ermoglicht. Schlusselworter: Metallisierte Kohlenstofffasern / funktionelle CFK / galvanische Abscheidung Efficient lightweight construction requires intelligent materials that meet versatile functions. One approach to produce functional carbon fiber-reinforced plastics (CFRPs) is the metallization of carbon fiber fabrics. This results in a crack-free, homogeneous nickel layer on the fabrics’surfaces. By selecting suitable layer parameters, every single fiber of the entire fabrics will be evenly metallized and allow the application of functional CFRPs as lightweight hydrogen storage.

Warmedammschichtsysteme (WDS) bestehen in der Regel aus einer metallischen Haftschicht und einer keramischen Deckschicht. CoNiCrAlY-Superlegierungen finden als Haftschichtmaterial weit verbreiteten Einsatz, fur die Deckschichten wird oft Yttriumoxid-stabilisiertes Zirkondioxid verwendet. In der Folge der Langzeiteinwirkung von sauerstoffhaltigen Atmospharen bei hohen Temperaturen auf die Warmedammschichtsysteme kommt es zur Diffusion von Sauerstoff durch die porose Keramikschicht und zu Oxidationsprozessen an der inneren Grenzflache zur Haftschicht. Legierungskomponenten der Haftschicht bilden die so genannte thermisch gewachsene Oxidschicht. Das dabei auch entstehende α-Al2O3 behindert die Sauerstoff-Diffusion und verlangsamt so den Oxidationsprozess, was sich positiv auf die Einsatzdauer des Schichtsystems auswirkt. Die Verteilung der Legierungselemente in der Haftschicht bewirkt jedoch in der Regel die Bildung von gemischten Oxidphasen, wobei die Oxide unterschiedliche Wachstumsgeschwindigkeiten aufweisen, was zu lokalen Spannungen, Mikrorissen und Abplatzungen fuhrt. Dies beschrankt in hohem Mase die Lebensdauer von Warmedammschichtsystemen. In der vorliegenden Arbeit wird der Einfluss einer dunnen dampfabgeschiedenen Aluminium-Zwischenschicht auf die Eigenschaften eines thermisch gespritzten Warmedammschichtsystems untersucht. Die etwa 1 µm dicke Zwischenschicht wurde in einem zusatzlichen Prozessschritt zwischen Haft- und Deckschicht appliziert. Unter einsatznahen Auslagerungen in Atmospharenofen wurde erreicht, dass sich homogene α-Al2O3-reiche Oxidschichten bilden, die das Potenzial fur ein verlangsamtes bzw. kontrolliertes Wachstum der thermischen Oxidschicht besitzen. Erste Untersuchungsergebnisse zu Oberflachenbeschaffenheit, Mikrostruktur, chemischer Zusammensetzung und Spannungszustand vor und nach Temperaturwechselbelastungen werden fur die so modifizierten Warmedammschichtsysteme im Vergleich zu Standardsystemen dargestellt. Thermal barrier coatings (TBC) generally consist of a metallic bond coat (BC) and a ceramic top coat (TC). Co–Ni–Cr–Al–Y metallic super alloys and Yttria stabilised zirconia (YSZ) have been widely used as bond coat and top coat for thermal barrier coatings systems, respectively. As a result of long-term exposure of thermal barrier coatings systems to oxygen-containing atmospheres at high temperatures, a diffusion of oxygen through the porous ceramic layer occurs and consequently an oxidation zone is formed in the interface between ceramic top coat and metallic bond coat. Alloying components of the BC layer create a so-called thermally grown oxides layer (TGO). One included oxide type is α-Al2O3. α-Al2O3 lowers oxygen diffusion and thus slows down the oxidation process of the bond coat and consequently affects the service life of the coating system positively. The distribution of the alloying elements in the bond coat layer, however, generally causes the formation of mixed oxide phases. The different oxide phases have different growth rates, which cause local stresses, micro-cracking and, finally, delamination and failure of the ceramic top coat layer. In the present study, a thin Al inter-layer was deposited by DC-Magnetron Sputtering on top of the Co–Ni–Cr–Al–Y metallic bond coat, followed by thermal spraying of yttria-stabilised zirconia (YSZ) as a top coat layer. The deposited Al inter-layer is meant to transform under operating conditions into a closed layer with high share of α-Al2O3 that slows down the growth rate of the resulting thermally grown oxides layer. Surface morphology and microstructure characteristics as well as thermal cycling behaviour were investigated to study the effect of the intermediate Al layer on the oxidation of the bond coat compared to standard system. The system with Al inter-layer shows a smaller thermally grown oxides layer thickness compared to standard system after thermal cycling under same conditions.