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CLUSTER OF EXCELLENCE MERGE
Research

Research Areas


The superordinate interacting research domains (IRD) in the Cluster of Excellence, such as the technology-oriented core areas for investigating and developing technologies for passive and active lightweight structures, have been derived with the research focus placed on the merging of proven key technologies for mass-production:

Research Areas MERGE

Semi-finished Products and Preform Technologies

Introduction

The focus of IRD A is on large-scale processes for the in-line combination of textiles, plastics and metals. The sensor integration via modular processing steps, complete the research programme and the entire manufacturing route. The investigations are aimed at add-on technologies for the merged manufacturing of semi-finished products and preforms, which will be applied in IRDs B, C and D. The emphasis is placed on the manufacture of multidirectional thermoplastic prepregs with direct impregnation and bionically arranged reinforcement structures in the tape-laying process. Furthermore, pure polymeric sheets with a defined property profile for hybrid structures will be used. The minimisation of handling and logistics complexity in hybrid semi-finished products, and the simultaneous reduction of process steps in order to decrease energy consumption and costs by means of process integration, are the most important drivers. This productivity gap will be closed through the development of an extended Fiber-Foil-Tape Unit (FFTU) and a new continuous orbital wrapping (COW) unit. Both units are intended for the manufacture of tailored multi-axial hybrid composites and structures with a defined combination of metallic, polymeric and textile components, with or without functionalisation.
The planned merging of currently separate technologies requires that methods and model systems describing universally applicable correlations found in technology-specific parameter combinations be prepared and demonstrated by means of in-line processes using the Wind Energy Rotor Blade (WERB) prototype as well as through in-situ integration into the Chemnitz- Car-Concept (CCC) and Conveyor Complex (CCX) prototypes. These demonstrators will be simulated and designed with the objective of high energy efficiency and reproducibility. This will involve the application of process-compatible sensitivity analyses and optimisation algorithms.

Scientific strategies

In order to fulfill the complex requirements in terms of performance, energy efficiency and sustainable costs, an in-line process is needed. According to the objectives of MERGE, this process must be variable in the supply of fiber-reinforced plastic (FRP) sheets, metallic foils or functional films by utilising an appropriately designed creel and corresponding process peripherals. The following scientific strategies are planned within the research programme of the sub-projects:

  • Large-scale manufacture of high-strength, high-stiffness hybrid material compounds
  • Provision of concepts for the in-line production of metal/plastics and metal/FRP multilayer composites for subsequent forming processes
  • Computational engineering COW technology for the manufacture of multi-axial, graded metal/FRP layer structures for plastics processing
  • Continuous fabrication of intelligent hybrid composites with sensory modules for structural health monitoring (SHM) systems
  • Investigation of flow processes suitable for the integration of discrete and continuously-printed electronic functional elements in semi-finished products and preforms
  • Development of innovative material concepts with biological patterns based on fiber-reinforced thermoplastics produced and processed with textile technologies
  • Adaptation of the manufacturing process of textile thermoplastic composites for an optimum design of structures with a biological pattern
  • Development of forming processes for the hybrid material to get near-net-shape parts
Figure: In-line process; Fibre Foil Tape Unit (FFTU), requirement-oriented material design
Figure: In-line process; Fibre Foil Tape Unit (FFTU),
requirement-oriented material design

Leader of research area
apl. Prof. Dr.-Ing. habil. Daisy J. Nestler
Technische Universität Chemnitz
Professorship Composite Materials

Investigators

Subprojects of the IRD A
IRD A1 Large-scale manufacture of high-strength, high-stiffness hybrid material composites
IRD A2 Fold-winding technology for multi-axial, multiply prepregs (MMP) and the continuous orbital wrapping process
IRD A3 Development of bionic, semi-finished functional products and physically compatible hybrid components
IRD A4 Continuous fabrication of hybrid composites with sensing and actuating modules for structural-health monitoring systems

Metal-intensive Technologies

Introduction

Within hybrid lightweight structures, metallic materials have numerous advantages regarding the close-up transmission of loads and stable behaviour during disturbances. What’s more, the wide variety of potential materials and their characteristics, as well as their economical and ecological production and manufacturing, argue in favour of metallic components. The combination of the advantages of both metals and FRP can be achieved through sustainable merging technologies within component manufacturing. The setting of the compound and its further shape forming, preferably within just a few steps can be carried out favourably in just a single process. Thus, technologies for the integration of semi-finished products and preforms with subsequent shape forming on the one hand, and in-situ technologies for hybrid production and shape forming on the other hand, are to be examined in one institutional process. In order to achieve this, the focus will be placed on basic metallic structures such as metal sheets and profiles, metal foams, fibers and conductors. The scientific challenge lies in finding a resource-efficient and functional integration strategy (geometrically, mechanically, thermally, sensory/actuatory) by merging adequate processes while still preserving the character of series production.

Scientific strategies

The scientific investigations on resource-efficient processes for lightweight hybrid structures, based on metal frameworks and their production technologies, will pursue the following scientific strategies within the research programme of the subprojects:

  • Development of sandwich structures with metal foam and surface layers of fiber compounds
  • Integrated management of process parameters for metal foam and injection moulding
  • Development of a modular tool concept with integrated sensors and actuators as well as elements for local cooling and heating in order to control the local stress and temperature distribution in the case of plastic-based high-pressure forming
  • Adjustment of thermal and rheological process parameters to combine metal forming and plastic injection moulding processes
  • Enhancement of process limits of metal forming by means of increased hydrostatic pressure based on integrated injection moulding processes
  • Planning methods of evaluation and designing processes for hybrid components
  • Further development of IT tools for knowledge management and process planning
  • Development of highly integrated 3D textiles with adaptive shape and stiffness, made using filaments of shape memory alloys, textile fibers and integrated electronics and sensors The validation of the solutions and methods will be realized by means of the design, simulation, manufacture and testing of basic structures and demonstrators. The selected solutions will be integrated into the system demonstrator CCC and tested under driving conditions. Solutions for the sensor integration will be incorporated into the system demonstrator WERB. The research activities in IRD B will be done in cooperation with the Fraunhofer IWU.
Figure: Functional enhancement of metal-intensive technologies for manufacturing of hybrid metal/plastics composites; Metal or FRP deep drawing and creation of complex secondary design elements by injection molding
Figure: Functional enhancement of metal-intensive technologies for manufacturing of hybrid metal/plastics composites; Metal or FRP deep drawing and creation of complex secondary design elements by injection molding

Leader of research area
Univ.-Prof. Dr.-Ing. Welf-Guntram Drossel
Fraunhofer Institute for Machine Tools and Forming Technology IWU

Investigators

Subprojects of the IRD B
IRD B1 Metal foam lightweight structures bonded with fibre-reinforced plastics
IRD B2 Forming based on operating media for the in-situ manufacture of metals/plastics structures
IRD B3 Integration of transition layers and manufacture of high-precision functional surfaces on metal-based hybrids
IRD B4 Resource-efficient processes for manufacturing hybrid structures
IRD B5 Functional hybrid textiles with passive and active metal filaments

Textile-/Plastics-based Technologies

Introduction

The anisotropic properties of textile-reinforced plastic composites allow for a force-flow-compatible exploitation of the extraordinary lightweight potential with high-density performance and functionality, but require new technologies as well as complex simulation and design methods. In order to fully exploit the high specific strengths and stiffnesses in lightweight structures, the integration of metallic load introduction systems is generally indispensable. The varying fiber orientation of textile-reinforced components and the specific restrictions imposed by the complex manufacturing process complicate the force-flow-compatible design of embedded metal components with regard to maximum structure strength. The same applies to short- and long-fiberreinforced thermoplastic components with metal inserts using the injection moulding process.
With the development of integrative injection moulding processes in association with in-mould coating, a vital contribution is made to the reduction of resource and energy consumption, especially for the areas of fiber-reinforced plastics (FRP) and metal/ plastic composites. Even when lightweight construction technologies for composite fiber structures made from natural fibers and biodegradable polymers are available, environmental conditions must be taken into account.
To validate the research methods that have been developed, representative fundamental components and demonstrators will be utilised, with a progressive increase in complexity expected throughout the course of the project. The preferred designs will be fabricated in the integrative lightweight manufacturing complex (ILCx), integrated into the primary system demonstrator, the Chemnitz-Car-Concept (CCC), and tested under typical vehicle loads and environmental conditions.

Scientific strategies

Taking into consideration the selected research methods of the sub-projects, in order to realise the intended injection-moulding- based process merging for the production of multifunctional lightweight structures in hybrid construction, the following scientific strategies are necessary:

  • Development of methods for merging similar operating principles within the injection moulding of FRP/metal lightweight structures and in-mould surface functionalisation
  • Topology and fiber composite optimisation of load-flow-compatible textile preforms, restricted by stretched thread embedding in the plastics components
  • Multi-component injection moulding technology for the in-situ contacting and combination of active elements by means of electroconductive and insulating thermoplastics
  • Merging of injection moulding and tape-laying technologies for packaging miniaturised electronic modules for the manufacture of microelectromechanical systems
  • Development of highly filled hybrid multifunctional components and their processes for the manufacture of lightweight composites from natural fibers with biodegradable polymers
  • Evaluation of the process-adapted mechanical properties of physiologically compatible textile/plastic components by observing the anisotropic effects

In order to validate the compiled approaches and methods, various fundamental components must be designed, produced and tested. Throughout the course of the Cluster, it is expected that the complexity of the hybrid lightweight structures and consolidated technologies will increase progressively. During the application phase, the preferred designs will be integrated into the primary system demonstrator, the Chemnitz-Car-Concept (CCC), and extensively tested.

Figure: In-situ processes, use of new injection moulding for combination of hybrid components with additional smart applications
Figure: In-situ processes, use of new injection moulding for combination of hybrid components with additional smart applications

Leader of research area
Univ.-Prof. Dr.-Ing. habil. Prof. E. h. Prof. Lothar Kroll
Technische Universität Chemnitz
Professorship of Lightweight Structures and Polymer Technology

Investigators

Subprojects of the IRD C
IRD C1 MERGE technologies with textile/metal components and functional surfaces using integrative in-mould plastics processes for the CCC system demonstrator
IRD C2 Process merger of metal die casting/plastics injection moulding technologies for components of lightweight conveyor systems
IRD C3 Mass production enabled manufacturing and measurement technologies for sensoric and hybrid laminates
IRD C4 Flexible textile/plastics processes with renewable raw materials
IRD C5 MERGE technologies for physiologically compatible textile/plastic components using anisotropic effects

Micro- and Nanosystems Integration

Introduction

The integration of microelectronic components into hybrid structures allows for the functionalisation by sensors, actuators and electronics, and thus, the further improvement of the performance and functional density of hybrid components. Innovative continuous manufacturing technologies for active systems based on micro- and nanoeffects offer special advantages that enable the integration of functional elements into semi-finished products and preforms. In order to achieve a reliable integration of additional functionality, methods will be developed for the design and integration of active transducer elements in lightweight structures. The final goal is to enable the components to exhibit their intrinsic actuatory and sensory effect. This will be accomplished by means of a combination of in-situ and in-line processes, including injection moulding with functionalised textile layers for electrical contacting and mass print technology.
Due to an increased use of FRP components for the reduction of energy consumption in mobile applications, the condition monitoring of these lightweight structures is of increasing importance. One highly innovative approach is that of in-situ functionalization during production by means of in-mould-coating techniques and integration of nanocrystal-based sensor films. The integration of transducers and electronics into load-adapted FRP components requires novel interconnection, attachment and housing technologies. The major research objectives are the performance and reliability of signal transfer from hybrid structures to sensors and actuators, as well as the energy supply and response data linkage regarding cost-efficient production processes.

Scientific strategies

Within the scope of this research domain, methods will be developed for intelligent lightweight structures with increased functional density and, in keeping with the BRE strategy, will exhibit a high degree of resource savings through the merging and optimisation of existing successively coupled process chains. The research activities will consider all aspects of such “smart” textile lightweight structures and systems, including system design, technology development for the integration of sensing and actuation functionalities, power supply and communication, and also reliability investigations. Therefore, the four main sub-projects (D1 to D4) are strongly networked and focus on the following research fields:

  • Development of novel design methods together with their associated in-situ technologies for the integration of electromechanical transducers into heterogeneous composite components and the conception of models and instruments for economic evaluation of hybrid technologies
  • In-line manufacturing strategies for integrating innovative, foil-based sensors and generators
  • Integration of power supply and transfer for those sensors and generators
  • Communication methods for sensors and actuators by means of system-integrated metamaterials
  • Integration of silicon-based sensor systems, as well as reliability investigation and failure detection in FRP components

To enhance the resource efficiency, it is necessary to integrate the sensing, actuating and electronic elements directly during the fabrication processes. In addition to the investigation of technologies for the material integration of silicon sensors, one challenge is the understanding and controlling of mutual interactions between the sensor and the composite. As an innovative approach to monitoring the load conditions of lightweight components, large-scale, film-based sensors should be integrated into these structures to visualise a stress state through a colour change.
The integration of extremely small sensors, actuators and units for data processing and communication facilitates innovative applications but also requires new integration concepts. Aside from that, power transfer and communication are crucial in view of the high density of these intelligent sensor nodes that necessitate the development of new innovative wireless power and information transfer methods. In order to ensure a higher level of reliability, as well as lower production and operating costs for these new lightweight components, concepts will be provided for the evaluation of the achievable profit related to the applied resources.

Figure: In-situ Plastics Processes, Smart Systems Integration - Making preforms smarter by integration of new functionalities into hybrid structures
Figure: In-situ Plastics Processes, Smart Systems Integration - Making preforms smarter by integration of new functionalities into hybrid structures
Figure: In-situ Plastics Processes, Smart Systems Integration - Making preforms smarter by integration of new functionalities into hybrid structures

Leader of research area
Prof. Dr. Prof. h.c. Thomas Otto
Technische Universität Chemnitz
Professorship of Microtechnology

Investigators

Subprojects of the IRD D
IRD D1 Design methods and technologies for the integration of electronic functional elements into heterogeneous composites
IRD D2 Technologies for embedding foil-based sensors and generators
IRD D3 Technology for the integration of metamaterials for power transfer and communication
IRD D4 Technologies for the integration of miniaturised silicon sensor systems for failure detection in hybrid components

Interface technologies, Interface Engineering

Introduction

The combination of various groups of materials in function-optimised, hybrid lightweight construction requires the implementation of defined interface bonds, which must be consistent with the requirements placed on strength, stiffness, corrosion, wear, ageing and other properties.
IRD E serves as a cross-sectional research area in which fundamental change mechanisms and phenomena for the best possible boundary layer bonding of FRP, polymer and metal systems will be investigated. Since excessive stresses caused by both process-related and operational loads are induced in the boundary layer, the focus of the development work will be on the realisation of high, interlaminar tensile and shear strengths. Therefore, an appropriate interface design using chemical or mechanical surface modification, as well as the coating of adhesion-supporting intermediate layers, must be developed. Moreover, punctual and two-dimensional joining and contacting techniques require the equipping of functionalised surfaces of the plastic or FRP substrate with electronic devices. Reliable, low-energy joining and contacting processes that result in high mechanical and thermal joint strengths, as well as high-speed forming processes, are to be developed paying special consideration to the processing temperature and handling. By means of materials selection, interface compatibilisation and adjusted joining techniques, the coefficient of thermal expansion will be tailored. In this way, residual stresses during processing and service time can be managed sufficiently.

Scientific strategies

The scientific challenge of the IRD E is to design, adjust and model the interface – the weak spot of composite materials. The combination of different material classes in lightweight structures requires defined interface interactions on the micro-, meso- and macroscale. The different thermal expansion of the individual components as a function of the process parameters often leads to residual stresses in the interface, thus warping the hybrid composites. To create long-term use of polymer-metal interfaces, monomers will be synthesised suitable to polymerise and simultaneously form covalent bonds. This is controlled by the composition of the monomer which contains weak chemical bonds, suitable for reacting by heat during the manufacturing process (injection moulding, press technology). In this respect, particular attention will be paid to storability and reactivity. The assessment of the present interface requires suitable methods, mainly nanoindentation, microdiffractometry, highresolution microscopy and microelectrochemical techniques. Local mechanical properties will be determined through impact hardness and impact modulus tests. The obtained data is the basis for detailed design and adjustment of the diverse interfaces. As part of the strengthening to apply the new hybrid components, static and cyclic loading as well as fracture conditions have to be identified. High-cycle fatigue tests, crack growth measurements and the evaluation of the fracture toughness will be analysed.
To realise low-melting solders applied by nanoprinting, systematic investigations are intended to be conducted on the influence of the particle grain sizes, fractions and distributions of nanograined solder suspensions on the printing and subsequent soldering process. In order to achieve the wide variety of suspension parameters, solders based either on transition metal complexes or nanoparticle-filled organic binders will be developed.

Figure: Conductor track, printed with new low temperature metal-precursor
Figure: Conductor track, printed with new low temperature metal-precursor
Figure: Microstructuring of contact areas to enhance adhesion
Figure: Microstructuring of contact areas to enhance adhesion
Figure: Schematic diagram of metal ultrasonic joining
Figure: Schematic diagram of metal ultrasonic joining

Leader of research area
Univ.-Prof. Dr.-Ing. habil. Thomas Lampke
Technische Universität Chemnitz
Professorship of Materials and Surface Engineering

Investigators

Subprojects of the IRD E
IRD E1 Interface optimisation of metal- and polymer-based manufacturing processes for load-compatible hybrid components
IRD E2 Interface design for the integration of micro- and nanoelectronic systems into hybrid components

Modelling, Integrative Simulation and Optimisation

Introduction

The main objective of the interdisciplinary cross-sectional research area IRD F is the simulation, optimisation and design of the multifunctional lightweight structures under investigation within the MERGE Cluster. The component properties of the various material combinations depend to a great extent on the respective manufacturing processes, meaning the manufacturing and design conditions cannot be examined separately. Thus, a bivalent optimisation, including fully parameterised simulations of the manufacturing process as well as calculations of operating load cases of the resulting hybrid structured components, will be undertaken. This enormous computational task will be supported by efficient data management techniques and the use of distributed computing environments.
Moreover, the formation and the effect of manufacture-related residual stresses will be investigated experimentally and implemented within FE simulations in order to precisely model multi-material design components. The verification of the developed methods and approaches will be based on the hybrid basic components and system demonstrators of the MERGE Cluster.

Scientific strategies

In order to realize the main objectives of the IRD F, the following scientific strategies are necessary:

  • Experimental characterisation of residual stresses
  • Further development of adaptive FEM using error estimators and error indicators
  • Analysis and post processing concerning residual stresses and failure modes
  • Formulation of constitutive equations for the reinforced thermoplastic material with phase transition effects, anisotropy and residual stresses
  • Development of a parameterised FEM simulation tool for the hybrid structure
  • Bivalent optimisation with high-efficient computing strategies
Figure: Modelling, Integrative Simulation and Optimisation; Resource efficiency by goal-directed development and saving prototypes with the help of integrative simulation and simultaneous optimisation of manufacturing and design conditions
Figure: Modelling, Integrative Simulation and Optimisation; Resource efficiency by goal-directed development and saving prototypes with the help of integrative simulation and simultaneous optimisation of manufacturing and design conditions

Leader of research area
Univ.-Prof. Dr.-Ing. habil. Jörn Ihlemann
Technische Universität Chemnitz
Professorship of Mechanics of Solids

Investigators

Subprojects of the IRD F
IRD F1 Adaptive high-precision Finite Element Method for the simulation of hybrid structures using advanced constitutive laws and characterisation methods
IRD F2 Multi-criteria optimisation of coupled simulations of manufacturing processes and components with efficient data management and parallel computing

Networking Area

The task of the networking area is the interdisciplinary support of the research work in the various IRDs. By targeted internal networking activities the knowledge of the IRDs were brought together to provide fundamental technologies suitable for the resource-efficient mass-production of lightweight structures. In addition to these internal activities the external networking with industrial partners is another goal of the networking area. The intention is to ensure that the approaches based on basic research get viable into industrial processes in the medium term.

Furthermore, the networking area is involved in the activities of the roadmap team. The task of the roadmap team is to analyse systematically, schedule and prioritize the own research activities as well as the analysis of international research activities.

Finally, the networking area is also responsible for including research results in the development of contents of teaching especially in the planned PhD-programme in an appropriate manner. In this way, the excellence education of young researchers can be secured.

Figure: Integration of the networking area into the Cluster of Excellence MERGE
Figure: Integration of the networking area into the Cluster of Excellence MERGE