Composites have now revolutionized most industries, like aerospace, marine, electrical, transportation, and have proved to be a worthy alternative to other traditional materials. However for a further comprehensive usage, the tailorability of hybrid composites according to the specific application needs on a large-scale production basis is required. In this regard, one of the major fundamental research fields here involves a technology development based on the multiaxial warp-knitting technique for the production of bionic-inspired and application-specific textile preforms that are force compliant and exhibit multi-material design. This article presents a newly developed yarn (warp) path manipulation unit for multiaxial warp-knitting machines that enables a targeted production of customized textile preforms with the above characteristics. The technological development cycle and their experimental validation to demonstrate the feasibility of new technology through production of some patterns for different field of applications are then discussed.

Multi-material-design (MMD) is commonly realized through the combination of thin sheet metal and fibre reinforced plastics (FRP). To maximize the high lightweight potential of the material groups within a multi-material system as good as possible, a material-adapted and particularly fibre adjusted joining technology must be applied. The present paper focuses on two novel joining technologies, the Flow Drill Joining (FDJ) method and Spin-Blind-Riveting (SBR), which were developed for joining heavy-duty metal/composite hybrids. Tests were carried out with material combinations which are significant for lightweight constructions such as aluminium (AA5083) and carbon fibre-reinforced polyamide in sheet thickness of 1.8 mm. The mechanical testing and manufacturing of those multi-material joints was investigated.

Multi-material-design (MMD) is commonly realized through the combination of thin sheet metal and fibre reinforced plastics (FRP). To maximize the high lightweight potential of the material groups within a multi-material system as good as possible, a material-adapted and particularly fibre adjusted joining technology must be applied. The present paper focuses on two novel joining technologies, the Flow Drill Joining (FDJ) method and Spin-Blind-Riveting (SBR), which were developed for joining heavy-duty metal/composite hybrids. Tests were carried out with material combinations which are significant for lightweight constructions such as aluminium (AA5083) and carbon fibre-reinforced polyamide in sheet thickness of 1.8 mm. The mechanical testing and manufacturing of those multi-material joints was investigated.

<p>The design of vehicle components for crashworthiness is one of the most challenging problems in the automotive industry. The safety of the occupants during a crash event relies on the energy absorption capability of vehicle structures. Therefore, the body components of a vehicle are required to be lightweight and highly integrated structures. Moreover, reducing vehicle weight is another crucial design requirement since fuel economy is directly related to the mass of a vehicle. In order to address these requirements, various design concepts for vehicle bodies have been proposed using high-strength steel and different aluminum alloys. However, the price factor has always been an obstacle to completely replace regular body steels with more advanced alloys. To this end, the integration of numerical simulation and structural optimization techniques has been widely practiced addressing these requirements. Advancements in nonlinear structural design have shown the promising potential to generate innovative, safe, and lightweight vehicle structures. In addition, the implementation of structural optimization techniques has the capability to shorten the design cycle time for new models. A reduced design cycle time can provide the automakers with an opportunity to stay ahead of their competitors. During the last few decades, enormous structural optimization methods were proposed. A vast majority of these methods use mathematical programming for optimization, a method that relies on availability sensitivity analysis of objective functions. Thus, due to the necessity of sensitivity analyses, these methods remain limited to linear (or partially nonlinear) material models under static loading conditions. In other words, these methods are no able to capture all non-linearities involved in multi-body crash simulation. As an alternative solution, heuristic approaches, which do need sensitivity analyses, have been developed to address structural optimization problems for crashworthiness. The Hybrid Cellular Automaton (HCA), as a bio-inspired algorithm, is a well-practiced heuristic method that has shown promising capabilities in the structural design for vehicle components. The HCA has been continuously developed during the last two decades and designated to solve specific structural design applications. Despite all advancements, some fundamental aspects of the algorithm are still not adequately addressed in the literature. For instance, the HCA numerically implemented as a closed-loop control system. The local controllers, which dictate the design variable updates, need parameter tuning to efficiently solve different sets of problems. Previous studies suggest that one can identify some default values for the controllers. However, still, there is no well-organized strategy to tune these parameters, and proper tuning still relies on the designer’s experience.</p> <p> </p> <p> Moreover, structures with multiple materials have now become one of the perceived necessities for the automotive industry to address vehicle design requirements such as weight, safety, and cost. However, structural design methods for crashworthiness, including the HCA, are mainly applied to binary structural design problems. Furthermore, the conventional methods for the design of multi-material structures do not fully utilize the capabilities of premium materials. In other words, the development of a well-established method for the design of multi-material structures and capable of considering the cost of the materials, bonding between different materials (especially categorical materials), and manufacturing considering is still an open problem. Lastly, the HCA algorithm relies only on one hyper-parameter, the mass fraction, to synthesize structures. For a given problem, the HCA only provides one design option directed by the mass constraint. In other words, the HCA cannot tailor the dynamic response of the structure, namely, intrusion and deceleration profiles.</p> <p> </p> <p>The main objective of this dissertation is to develop new methodologies to design structures for crashworthiness applications. These methods are built upon the HCA algorithm. The first contribution is about introducing s self-tuning scheme for the controller of the algorithm. The proposed strategy eliminates the need to manually tune the controller for different problems and improve the computational performance and numerical stability. The second contribution of this dissertation is to develop a systematic approach to design multi-material crashworthy structures. To this end, the HCA algorithm is integrated with an ordered multi-material SIMP (Solid Isotropic Material with Penalization) interpolation. The proposed multi-material HCA (MMHCA) framework is a computationally efficient method since no additional design variables are introduced. The MMHCA can synthesize multi-material structures subjected to volume fraction constraints. In addition, an elemental bonding method is introduced to simulate the laser welding applied to multi-material structures. The effect of the bonding strength on the final topology designs is studied using numerical simulations. In the last step, after obtaining the multi-material designs, the HCA is implemented to remove the desired number of bonding elements and reduce the weld length.</p> <p> </p> <p>The third contribution of this dissertation is to introduce a new Cluster-based Structural Optimization method (CBSO) for the design of multi-material structures. This contribution introduces a new Cluster Validity Index with manufacturing considerations referred to as CVI_m. The proposed index can characterize the quality of the cluster in structural design considering volume fraction, size, interface as a measure of manufacturability. This multi-material structural design approach comprises three main steps: generating the conceptual design using adaptive HCA algorithm, clustering of the design domain using Multi-objective Genetic Algorithm (MOGA) optimization. In the third step, MOGA optimization is used to choose categorical materials in order to optimize the crash indicators (e.g., peak intrusion, peak contact force, load uniformity) or the cost of the raw materials. The effectiveness of the algorithm is investigated using numerical examples.</p>

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).

Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material- adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and faulttolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.

Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material- adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and faulttolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.

Vielschichtige Eigenschaftsprofile benötigen zunehmend moderne Verbundwerkstoffe und Werkstoffverbunde einschließlich der raschen Entfaltung neuer Fertigungstechnologien, da der monolithische Werkstoff bzw. ein einziger Werkstoff den heutigen komplexen Anforderungen nicht mehr genügen kann. Zukünftige Werkstoffsysteme haben wirtschaftlich eine Schlüsselposition und sind auf den Wachstumsmärkten von grundlegender Bedeutung. Gefragt sind maßgeschneiderte Leichtbauwerkstoffe (tailor-made composites) mit einem adaptierten Design. Dazu müssen Konzepte entwickelt werden, um die Kombination der Komponenten optimal zu gestalten. Das erfordert werkstoffspezifisches Wissen und Korrelationsvermögen sowie die Gestaltung komplexer Technologien, auch unter dem Aspekt der kontinuierlichen Massen- und Großserienfertigung (in-line, in-situ) und damit der Kostenreduzierung bislang teurer Verbundwerkstoffe und Werkstoffverbunde. In der vorliegenden Arbeit wird in vergleichbarer und vergleichender Art und Weise sowie abstrahierter Form ein Bogen über das Gesamtgebiet der Verbundwerkstoffe und Werkstoffverbunde gespannt. Eine zusammenfassende Publikation über dieses noch sehr junge, aber bereits breit aufgestellte Wissenschaftsgebiet fehlt bislang. Das ist der Separierung der einzelnen, fest aufgeteilten Gruppierungen der Verbundwerkstoffe geschuldet. Querverbindungen werden selten hergestellt. Dieses Defizit in einem gewissen Maße auszugleichen, ist Ziel der Arbeit. Besondere Berücksichtigung finden Begriffsbestimmungen und Klassifikationen, Herstellungsverfahren und Eigenschaften der Werkstoffe. Es werden klare Strukturierungen und Übersichten herausgearbeitet. Zuordnungen von etablierten und neuen Technologien sollen zur Begriffsstabilität der Terminologien „Mischbauweise“ und „Hybrider Verbund“ beitragen. Zudem wird die Problematik „Recycling und Recyclingtechnologien“ diskutiert. Zusammenfassend werden Handlungsfelder zukünftiger Forschungs- und Entwicklungsprojekte spezifiziert. Aus dem Blickwinkel der verschiedenen Herstellungsrouten insbesondere für Halbzeuge und Bauteile und der dabei gewonnenen Erkenntnisse werden verallgemeinerte Konzepte für tailor-made Verbundwerkstoffe und Werkstoffverbunde vorgeschlagen („Stellschraubenschema“). Diese allgemeinen Werkstoffkonzepte werden auf eigene aktuelle Forschungsprojekte der Schwerpunktthemen Metallmatrix- und Polymermatrix-Verbundwerkstoffe sowie der hybriden Werkstoffverbunde appliziert. Forschungsfelder für zukünftige Projekte werden abgeleitet. Besonderes Augenmerk gilt den hybriden Verbunden als tragende Säule zukünftiger Entwicklungen im Leichtbau. Hier spielen in-line- und in-situ-Prozesse eine entscheidende Rolle für eine großseriennahe, kosteneffiziente und ressourcenschonende Produktion. / Complex property profiles require increasingly advanced composite materials and material compounds, including the rapid deployment of new production technologies, because the monolithic material or a single material can no longer satisfy today's complex requirements. Future material systems are fundamentally important to growth markets, in which they have an economically key position. Tailor-made lightweight materials (tailor-made composites) with an adapted design are needed. These concepts have to be developed to design the optimum combination of components. This requires material-specific knowledge and the ability to make correlations, as well as the design of complex technologies. Continuous large-scale and mass production (in-line, in-situ), thus reducing the costs of previously expensive composite materials and material compounds, is also necessary. The present work spans the entire field of composite materials and material compounds in a comparable and comparative manner and abstract form. A summarizing publication on this still very new, but already broad-based scientific field is not yet available. The separation of the individual, firmly divided groups of the composite materials is the reason for this. Cross-connections are rarely made. The objective of this work is to compensate to some extent for this deficiency. Special consideration is given to definitions and classifications, manufacturing processes and the properties of the materials. Clear structures and overviews are presented. Mapping established and new technologies will contribute to the stability of the terms "mixed material compounds" and "hybrid material compounds". In addition, the problem of recycling and recycling technologies is discussed. In summary, areas for future research and development projects will be specified. Generalized concepts for tailor-made composite materials and material compounds are proposed ("adjusting screw scheme") with an eye toward various production routes, especially for semi-finished products and components, and the associated findings. These general material concepts are applied to own current research projects pertaining to metal-matrix and polymer-matrix composites and hybrid material compounds. Research fields for future projects are extrapolated. Particular attention is paid to hybrid material compounds as the mainstay of future developments in lightweight construction. In-line and in-situ processes play a key role for large-scale, cost- and resource-efficient production.

Vielschichtige Eigenschaftsprofile benötigen zunehmend moderne Verbundwerkstoffe und Werkstoffverbunde einschließlich der raschen Entfaltung neuer Fertigungstechnologien, da der monolithische Werkstoff bzw. ein einziger Werkstoff den heutigen komplexen Anforderungen nicht mehr genügen kann. Zukünftige Werkstoffsysteme haben wirtschaftlich eine Schlüsselposition und sind auf den Wachstumsmärkten von grundlegender Bedeutung. Gefragt sind maßgeschneiderte Leichtbauwerkstoffe (tailor-made composites) mit einem adaptierten Design. Dazu müssen Konzepte entwickelt werden, um die Kombination der Komponenten optimal zu gestalten. Das erfordert werkstoffspezifisches Wissen und Korrelationsvermögen sowie die Gestaltung komplexer Technologien, auch unter dem Aspekt der kontinuierlichen Massen- und Großserienfertigung (in-line, in-situ) und damit der Kostenreduzierung bislang teurer Verbundwerkstoffe und Werkstoffverbunde. In der vorliegenden Arbeit wird in vergleichbarer und vergleichender Art und Weise sowie abstrahierter Form ein Bogen über das Gesamtgebiet der Verbundwerkstoffe und Werkstoffverbunde gespannt. Eine zusammenfassende Publikation über dieses noch sehr junge, aber bereits breit aufgestellte Wissenschaftsgebiet fehlt bislang. Das ist der Separierung der einzelnen, fest aufgeteilten Gruppierungen der Verbundwerkstoffe geschuldet. Querverbindungen werden selten hergestellt. Dieses Defizit in einem gewissen Maße auszugleichen, ist Ziel der Arbeit. Besondere Berücksichtigung finden Begriffsbestimmungen und Klassifikationen, Herstellungsverfahren und Eigenschaften der Werkstoffe. Es werden klare Strukturierungen und Übersichten herausgearbeitet. Zuordnungen von etablierten und neuen Technologien sollen zur Begriffsstabilität der Terminologien „Mischbauweise“ und „Hybrider Verbund“ beitragen. Zudem wird die Problematik „Recycling und Recyclingtechnologien“ diskutiert. Zusammenfassend werden Handlungsfelder zukünftiger Forschungs- und Entwicklungsprojekte spezifiziert. Aus dem Blickwinkel der verschiedenen Herstellungsrouten insbesondere für Halbzeuge und Bauteile und der dabei gewonnenen Erkenntnisse werden verallgemeinerte Konzepte für tailor-made Verbundwerkstoffe und Werkstoffverbunde vorgeschlagen („Stellschraubenschema“). Diese allgemeinen Werkstoffkonzepte werden auf eigene aktuelle Forschungsprojekte der Schwerpunktthemen Metallmatrix- und Polymermatrix-Verbundwerkstoffe sowie der hybriden Werkstoffverbunde appliziert. Forschungsfelder für zukünftige Projekte werden abgeleitet. Besonderes Augenmerk gilt den hybriden Verbunden als tragende Säule zukünftiger Entwicklungen im Leichtbau. Hier spielen in-line- und in-situ-Prozesse eine entscheidende Rolle für eine großseriennahe, kosteneffiziente und ressourcenschonende Produktion. / Complex property profiles require increasingly advanced composite materials and material compounds, including the rapid deployment of new production technologies, because the monolithic material or a single material can no longer satisfy today's complex requirements. Future material systems are fundamentally important to growth markets, in which they have an economically key position. Tailor-made lightweight materials (tailor-made composites) with an adapted design are needed. These concepts have to be developed to design the optimum combination of components. This requires material-specific knowledge and the ability to make correlations, as well as the design of complex technologies. Continuous large-scale and mass production (in-line, in-situ), thus reducing the costs of previously expensive composite materials and material compounds, is also necessary. The present work spans the entire field of composite materials and material compounds in a comparable and comparative manner and abstract form. A summarizing publication on this still very new, but already broad-based scientific field is not yet available. The separation of the individual, firmly divided groups of the composite materials is the reason for this. Cross-connections are rarely made. The objective of this work is to compensate to some extent for this deficiency. Special consideration is given to definitions and classifications, manufacturing processes and the properties of the materials. Clear structures and overviews are presented. Mapping established and new technologies will contribute to the stability of the terms "mixed material compounds" and "hybrid material compounds". In addition, the problem of recycling and recycling technologies is discussed. In summary, areas for future research and development projects will be specified. Generalized concepts for tailor-made composite materials and material compounds are proposed ("adjusting screw scheme") with an eye toward various production routes, especially for semi-finished products and components, and the associated findings. These general material concepts are applied to own current research projects pertaining to metal-matrix and polymer-matrix composites and hybrid material compounds. Research fields for future projects are extrapolated. Particular attention is paid to hybrid material compounds as the mainstay of future developments in lightweight construction. In-line and in-situ processes play a key role for large-scale, cost- and resource-efficient production.

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).