Showing papers by "Maik Gude published in 2016"

Novel MRE/CFRP sandwich structures for adaptive vibration control

Abstract: The aim of this work was the development of sandwich structures formed by embedding magnetorheological elastomers (MRE) between constrained layers of carbon fibre–reinforced plastic (CFRP) laminates. The MREs were obtained by mechanical stirring of a reactive mixture of substrates with carbonyl-iron particles, followed by orienting the particles into chains under an external magnetic field. Samples with particle volume fractions of 11.5% and 33% were examined. The CFRP/MRE sandwich structures were obtained by compressing MREs samples between two CFRP laminates composed. The used A.S.SET resin was in powder form and the curing process was carried out during pressing with MRE. The microstructure of the manufactured sandwich beams was inspected using SEM. Moreover, the rheological and damping properties of the examined materials with and without a magnetic field were experimentally investigated. In addition, the free vibration responses of the adaptive three-layered MR beams were studied at different fixed magnetic field levels. The free vibration tests revealed that an applied non-homogeneous magnetic field causes a shift in natural frequency values and a reduction in the vibration amplitudes of the CFRP/MRE adaptive beams. The reduction in vibration amplitude was attributed mainly to the stiffening effect of the MRE core and only a minor contribution was made by the enhanced damping capacity, which was evidenced by the variation in damping ratio values.

Novel Hybrid Yarn Textile Thermoplastic Composites for Function-Integrating Multi-Material Lightweight Design : Novel Hybrid Yarn Textile Thermoplastic Composites…

Abstract: Future mobility applications are characterized by a high level of resource efficiency due to the application of novel lightweight materials and function-integrating, multi-material design concepts. Textile thermoplastic composites in particular pave the way for lightweight components characterized by highly specific mechanical properties and efficient production processes. This essay presents the strategy pursued by the Collaborative Research Centre SFB 639 “Textile-reinforced composite components for function-integrating multi-material design in complex lightweight applications”, a concept for the holistic analysis of complex process chains for hybrid yarn textile thermoplastic (HYTT) composites and the idea behind the innovative FiF electric mobility technology demonstrator vehicle.

Influence of processing parameters on the properties of carbon fibres – an overview

Abstract: Several studies have shown the importance of carbon fibres (CF) for different high technology markets. In recent years, different fibre types with improved properties have been developed for those markets. Polyacrylonitrile (PAN) copolymers are the basic raw material (precursor) for these fibres in the predominant case. Improvements of the mechanical fibre properties have mainly been achieved by defect reduction during the manufacturing process. Thus, commercial carbon fibres with tensile strengths up to approx. 7000 MPa are currently available. It can be shown that the strengths can be further increased (in the direction of graphene properties) when the relationship between process conditions and defects due to manufacturing of the fibres is better understood. In this context, novel processes like electron beam crosslinking or UV-activation have proven to be very promising. The article gives an overview about the current situation in the field of carbon fibres development and particularly shows recent shortcomings with respect to novel applications.

Experimental Characterisation of Fatigue Damage in Single Z-pins

Abstract: Z-pins have been shown to significantly improve delamination resistance and impact strength of carbon fibre reinforced (CFRP) composites. In this paper, an experimental investigation of the influence of different fatigue parameters (mean opening/sliding displacement, amplitude, frequency, number of cycles) on the through-thickness reinforcement (TTR) is presented. For mode I, it is shown that the degradation on pin behaviour during fatigue is mostly affected by the applied displacement amplitude. The degradation is primarily caused by surface wear. Due to the brittleness of the Z-pins, mode II fatigue does not have a significant effect for very small sliding displacements. Exceeding a critical displacement causes the pin to rupture within the very first cycles.

Biomimetic optimisation of branched fibre-reinforced composites in engineering by detailed analyses of biological concept generators.

Abstract: The aim of this study is the biomimetic optimisation of branched fibre-reinforced composites based on the detailed analysis of biological concept generators. The methods include analyses of the functional morphology and biomechanics of arborescent monocotyledons and columnar cacti as well as measurements and modelling of mechanical properties of biomimetic fibre-reinforced composites. The key results show evidence of notch stress reduction by optimised stem-branch-attachment morphology in monocotyledons and columnar cacti. It could be shown that some of these highly interesting properties can be transferred into biomimetic fibre-reinforced composites.

Forming of carbon fiber reinforced thermoplastic composite tubes – Experimental and numerical approaches

Abstract: Continuous-reinforced thermoplastic composites are of growing importance for series production of lightweight components in manifold industrial areas. Novel manufacturing technologies allow the production of hollow semi-finished products that are post formed to enhance functionality. To maximize efficiency in the development process of such components it is necessary to evaluate the forming processes numerically using Finite Elements (FE)-methods. The aim is to perform feasibility studies at an early stage, reduce development time by virtual process optimization and to generate a detailed understanding of the post formed fiber architecture for further structural-mechanical analysis.

Effect of environmentally-friendly flame retardants on fire resistance and mechanical properties of rigid polyurethane foams

Abstract: In this paper the new compositions of polyurethane foams with reduced flammability containing environmentally friendly flame retardants, such as ammonium polyphosphate, melamine pyrophosphate, triethyl phosphate, bentonite and expanded graphite obtained with long fiber injection (LFI) method have been presented. The effect of the addition of various flame retardants and their mixtures on the fire resistance and mechanical properties of the foams has been determined. An improvement in fire resistance of the modified polyurethane compositions has been observed. Manufactured polyurethane foams containing flame retardants have been classified as materials with flammability class V-0. The addition of flame retardants has not significantly deteriorated mechanical properties of the investigated materials.

A composite-appropriate integration method of thick functional components in fibre-reinforced plastics

Abstract: The use of integrated structural health monitoring systems for critical composite parts, such as wind turbine blades, fuselage and wing parts, is an promising approach to guarantee a safe and efficient operational lifetime of such components. Therefore, the integration of thick functional components like sensors, actuators and electronic components is often necessary. An optimal integration of such components should be ensured without material imperfections in the composite structure, i.e. voids and resin rich areas, and failure of the functional components. In this paper, first investigations were undertaken for a basic understanding of the mechanical performance of a fibre reinforced plastic component with integrated functional elements. The influence of different materials and treatment methods for the encapsulation of electronic components was experimentally investigated under static and dynamic loading tests. By means of a parametric finite element model, the effects of an encapsulation and various parameters such as the shape and orientation of the electronic components were examined. Several encapsulation variants were investigated in order to minimise the chance of failure initiations. Based both on experimental and numerical results, a preferred composite integration concept was selected for an electronic board and some first recommendations for an optimal integration were derived.

Experimental‐numerical test strategy for evaluation of curing simulation of complex‐shaped composite structures

Abstract: Numerical analyses of manufacturing processes become more and more essential, in particular for thick-walled and complex-shaped components made of fibre-reinforced thermosets. One of the main problems is the heat accumulation within those laminates caused by the exothermal reaction while curing the thermoset resin. To enable a precise and efficient prediction of the occurring temperatures within the laminate especially for industrial applications, a reliable and time-saving numerical analysis of curing processes is desirable. Therefore, a novel experimental-numerical test strategy for a precise prediction of the curing process is presented including both the analytical and experimental determination of numerous thermal and thermo-chemical material parameters and models for carbon fibre reinforced thermosets. Numerical validation steps are presented in order to evaluate reliability of experimentally determined material parameters and models. Additionally, the developed finite element model was adopted for the curing simulation of a large complex-shaped turbine fan blade with a thick-walled root section. Highlight of this work is the extensive experimental validation of the numerical analysed curing process.

Design of multi-scale-structured Al-CF/PA6 contour joints

Abstract: In contrast to common joining technologies for composite-metal hybrid structures such as bonding and riveting, contour joints offer promising potential in terms of manufacturing efficiency and mechanical performance For composite structures, joining systems with positive locking elements enable to pass high loads and are capable to achieve high degrees of material utilisation To enhance the performance of hybrids, a multi-scale structuring approach is sought Aiming at high rate production, especially in automotive industry, an intrinsic manufacturing approach whereat the composite part is joined to the metallic part during its consolidation process has been developed This paper demonstrates the intrinsic manufacturing principles of continuous fibre-reinforced thermoplastic hollow profiles with multi-scale-structured load introduction and mainly focuses on the development of a fibre appropriate design Based on a design of experiment approach, numerical parameter studies for the optimisation of macro contour have been carried out to create a general design guideline

Impregnation studies and mechanical characterization of cellular, natural, fiber-reinforced, composite structures

Abstract: With the use of natural fibers as a substitute for synthetic reinforcements, a significant contribution towards advanced ecological and efficient lightweight structures can be made. Within this article, the polyurethane (PUR) spray coat method is used for the manufacture of natural fiber-reinforced composites based on the fiber materials linen and hemp. Both the investigation of the mechanical properties and the yarn impregnation, as a reference for the composite quality, are of major interest and help to evaluate the potential of these bio-based materials as a contribution towards advanced lightweight components.

Influence of voids and impact damage on the fatigue behaviour of large scale composites

Abstract: Defects in laminated composite structures like voids and impact damages have a major influence on the fatigue behaviour. These defects may occur in the manufacturing process and during lifetime of composite parts and lead to matrix cracks within single layers and to delaminations between adjacent layers with different fibre orientations. We investigated the relationship between voids and impact damage and fatigue lifetime. Specimens made of a glass fibre non-crimp fabric were produced by vacuum assisted resin infusion. Voids were introduced by air-bypass simulating a leakage during the vacuum assisted resin infusion-process. Impact damage was induced using a canon. Stringer-panels with the basic dimensions of 1000 mm × 1200 mm and a radius of 1980 mm were tested under multiaxial load situations in a hexapod test rig and a tension/compression-shear test rig.

Intrinsic manufacture of hollow thermoplastic composite/metal structures

Abstract: In contrast to common and classical joining technologies for composite/metal hybrid structures such as bonding and riveting, profile and contour joints offer a promising potential for novel lightweight hybrid structures. First and foremost, joining systems with a form closure function enable to pass very high loads into rod- and tube-shaped fibre reinforced structures and achieve high degrees of material utilization for the composite part. This paper demonstrates the theoretical and technological principals for a resource efficient design and production of highly loaded thermoplastic composite profile structures with integrated metallic load introduction elements and a multi scale form closure. The hybrid structures are produced in an integral blow moulding process in which a braided tape-preform is simultaneously consolidated and formed into the metallic load introduction element. These metallic load introduction elements are manufactured in a two-stage process of external and internal hydroforming, afte...

Textile-Reinforced Thermoplastics for Compliant Mechanisms – Application and Material Phenomena

Abstract: Compliant mechanisms are single-piece structures obtaining their desired motion through elastic deformation of flexible parts. The performance of compliant mechanisms is highly dependent on the material properties, which have to be characterized over a wide range of loads. Textile glass fiber reinforced polypropylene is identified as valuable material for compliant structures. The material properties and damage phenomena for tension, shear and compression loading as well as for cyclic loading are elaborated under special consideration of elastic and inelastic deformations. Local strain measurements in the vicinity of an open hole sharpen the validity of homogenized models for textile reinforcements and directing towards multi-scale approaches for a localized deformation analysis.

Effect of HNT on the Microstructure, Thermal and Mechanical Properties of Al/FA CS -HNT Composites Produced by GPI

Abstract: To develop an optimised manufacturing method of fly ash-reinforced metal matrix composites, the preliminary tests were performed on the cenospheres selected from fly ash (FACS) with halloysite nanotubes (HNTs) addition. The preform made out of FACS with and without the addition of HNT (with 5 and 10 wt.%) has been infiltrated by the pure aluminium (Al) via adapted gas pressure infiltration process. This paper reveals the influence of HNT addition on the microstructure (analysis was done by computed tomography and scanning electron microscopy combined with energy-dispersive x-ray spectroscopy), thermal properties (thermal expansion coefficient, thermal conductivity and specific heat) and the mechanical properties (hardness and compression test) of manufactured composites. The analysis of structure-property relationships for Al/FACS-HNT composites produced shows that the addition of 5 wt.% of HNT to FACS preform contributes to receiving of the best mechanical and structural properties of investigated composites.

Funktionalisierte Faser-Thermoplast-Profilstrukturen

Abstract: Faser-Kunststoff-Verbunde (FKV) verfügen über ein breites und anpassungsfähiges Eigenschaftsspektrum, das für eine Vielzahl unterschiedlichster Anwendungen bereits vorteilhaft genutzt wird. Die hervorragenden spezifischen mechanischen Eigenschaften der Verstärkungsfasern ermöglichen bei lastpfadgerechter Ablage höchste Leichtbaugrade und bieten großes Potenzial für die Herstellung ressourceneffizienter LeichtbauStrukturen. Die Nutzung des Werkstoffpotenzials von FKV in Serienanwendungen setzt wirtschaftliche Herstellungsprozesse und eine Weiterentwicklung bisher noch stark manuell geprägter Fertigungsabläufe hin zu teilund vollautomatisierten Verarbeitungsprozessen mit signifikant verkürzten Taktzeiten voraus. Im Gegensatz zu FKV mit duroplastischer Matrix können FaserThermoplast-Verbunde (FTV) ohne chemische Reaktion des Matrixmaterials im Verarbeitungsprozess hergestellt werden und bieten

Deformation Analysis of Polymer Foams under Compression Load using in situ computed Tomography and Finite Element Simulation Methods

Abstract: Since different X-ray tomographic techniques offer advantageous characteristics, they frequently complete or even replace standard methods based on acoustic emission, thermography and ultrasonic. Especially the detection and evaluation of voids and cellular structures can be performed with a resolution of up to 1 μm and 3D visualization. Within this paper, a novel in situ CT device is used to perform compression tests on closed-cell polymeric foams with a defined foam density. Next to the determination of the cell structure with consideration of the pore size distribution and their morphology, the elastic compression behaviour is investigated. Following the analysis of the foam structure, the implementation of an implicit finite element model is developed based on computer tomographic scans. By the introduction of a phase field function to implicitly describe the foam structure, technical difficulties associated with meshing the complex structure can be avoided and the equations to describe the deformation behaviour are effectively solved on high performance computers. Beyond that, the results gained by the in situ CT device help to adapt and complete the currently available elastic deformation models and therefore offer the opportunity to predict the material behaviour for various load scenarios of polymeric foams.

Multiscale characterization and testing of function-integrative fiber-reinforced composites

Abstract: Smart fiber-reinforced composites, such as long fiber or textile-reinforced polymers are often functionalized by integration of piezoelectric transducers to realize sensory and actuatory tasks like condition and structural heath monitoring, energy harvesting or active vibration damping. Each of these tasks is connected with specific requirements with regard to the electromechanical behavior of the composite structure. In this chapter, several qualitative and quantitative methods including nondestructive, optical, electrical, and mechanical testing for the characterization of smart fiber-reinforced composites are described. Beyond their functionality and electromechanical performance, structural integrity and quality assurance are focused. By example of case studies, characterization of long fiber-reinforced thermoset and textile-reinforced thermoplastic polymers with specific test setup and results are shown. Novel developments in the field of sensor and actuator development and manufacture as well as integration of these functional elements into fiber-reinforced composites are presented.

Potential and application fields of lightweight hydraulic components in multi-material design

Abstract: Hydraulic systems are used in many fields of applications for different functions like energy storage in hybrid systems. Generally the mass of hydraulic systems plays a key role especially for mobile hydraulics (construction machines, trucks, cars) and hydraulic aircraft systems. The main product properties like energy efficiency or payload can be improved by reducing the mass. In this connection carbon fiber reinforced plastics (CFRP) with their superior specific strength and stiffness open up new chances to acquire new lightweight potentials compared to metallic components. However, complex quality control and failure identification slow down the substitution of metals by fiber-reinforced plastics (FRP). But the lower manufacturing temperatures of FRP compared to metals allow the integration of sensors within FRP-components. These sensors then can be advantageously used for many functions like quality control during the manufacturing process or structural health monitoring (SHM) for failure detection during their life cycle. Thus, lightweight hydraulic components made of composite materials as well as sensor integration in composite components are a main fields of research and development at the Institute of Lightweight Engineering and Polymer Technology (ILK) of the TU Dresden as well as at the Leichtbau-Zentrum Sachsen GmbH (LZS).

Forming of carbon fiber reinforced thermoplastic composite tubes - Experimental and numerical approaches

Abstract: Continuous-reinforced thermoplastic composites are of growing importance for series production of lightweight components in manifold industrial areas. Novel manufacturing technologies allow the production of hollow semi-finished products that are post formed to enhance functionality. To maximize efficiency in the development process of such components it is necessary to map the forming processes numerically using Finite Elements(FE)-methods. The aim is to perform feasibility studies at an early stage, reduce development time by virtual process optimization and to generate a detailed understanding of the post formed fiber architecture for further structural-mechanical analysis.

Faser-Kunststoff-Verbundhalbzeug und Verfahren zur Herstellung

Abstract: Gegenstand der vorliegenden Erfindung ist ein Verfahren zur kontinuierlichen Herstellung von Faserverbundhalbzeug und ein derart hergestelltes Faserverbundhalbzeug. Das im Verfahren eingesetzte Matrixmaterial weist einen Abstand zwischen Erweichungstemperatur und Vernetzungstemperatur auf. Im unvernetzten Zustand verfugt es uber thermoplastische und im vernetzten Zustand uber duroplastische Eigenschaften. Das Verfahren sieht das Aufbringen von Verstarkungsfasermaterial und unvernetztem Matrixmaterial auf ein Transportband und das Pressen von Verstarkungsfasermaterial und unvernetztem Matrixmaterial zu dem Faserverbundhalbzeug vor. Kennzeichnend ist, dass das Matrixmaterial wahrend des Pressens aufgrund einer Erwarmung in erweichtem Zustand vorliegt, jedoch dabei nicht vernetzt. Das erfindungsgemase Faserverbundhalbzeug bestehet aus Verstarkungsfasermaterial und mit diesem verpressten, unvernetztem Matrixmaterial, wobei das Matrixmaterial ein Einkomponenten-System ist, das einen deutlichen Abstand zwischen Erweichungstemperatur und Vernetzungstemperatur aufweist und das in diesem Temperaturbereich thermoplastisch umgeformt werden kann.