The battery systems of electrified vehicles are characterized by increasing weight due to larger battery modules. A lightweight battery carrier structure can reduce the system weight by replacing heavy metallic housing components with materials such as fiber-reinforced plastics (FRP) and aluminum. The battery housing must meet several requirements, e.g. stiffness, crash and intrusion protection and thermal management. Today’s battery housings are manufactured using die-cast or extrusion parts and are actively cooled. A novel approach is a lightweight hybrid battery housing consisting of a thermoformed FRP as a stiff outer shell and an integrated closed-cell aluminum foam infiltrated with phase change material (PCM) for passive thermal management. This multi-material structure enables the substitution of functionally separated systems in one intelligent solution. In the Open Hybrid LabFactory an entire process chain was established, including the aluminum foaming process, the thermoforming of FRP with heating and consolidating as well as the integrated forming and joining process of FRP with aluminum foam. With the goal of application-oriented research, a battery housing of an existing electric car was used to define requirements such as design space and mechanical specifications. Based on parameter studies an optimized process design was achieved, which is described in this paper.

Injection molding is an efficient manufacturing process for short-fiber reinforced plastic components and is used for the production of semi-structural or geometrically complex components. To improve stiffness and strength, continuous fibers can be locally integrated inside the part during manufacturing. A local integration of fibers is not feasible for high output manufacturing processes but can be achieved by direct impregnation of endless fibers in the injection molding process. It is a challenging option to integrate endless fibers in injection molded parts in means of fiber position and infiltration. Thereby, the knowledge of the flow process of the injected melt must be precisely understood in means of orientation of the fibers to achieve a correct position. In previous works the process parameters for the impregnation of fibers and the composite behavior of untreated fibers were investigated. As a result, the surface pretreatment of the fibers can have an important effect on the composite and the direct impregnation of fibers. An important focus of this work is the pretreatment of glass fibers by plasma. The influence of the plasma parameters resulting on the adhesion properties between fiber and matrix and thus the bond strength of the composite are evaluated and measures for further adhesive property improvement are shown.

Hot stamping of high strength steel parts is an established way to realize today ́s structural lightweight components in car bodies through sheet thickness reduction. The steel typically used for hot stamping is a boron-manganese 22MnB5 steel reaching up to 1,900 MPa in strength. New boron-manganese alloys achieving higher strength are expected to be developed, generating challenges for the manufacturing process by means of formability. Thus, a further reduction of steel thickness resulting in lighter components is not expected. Hybrid lightweight design approaches aim at weight reduction by reducing steel thickness and applying fiber-reinforced plastics (FRP) to regain structural stiffness and strength. The use of residual heat remaining from the hot stamping process allows to activate adhesives to bond FRP to hot stamped steel. The performances of adhesive bonds depend strongly on surface characteristics. To avoid scaling and decarburization during the heating process several coatings for hot stamped steels are used forming intermetallic layers through heat treatment. The most common coating in today’s automotive application is an Al-Si coating. Thus, the overall performance of the adhesive bonded hot stamped metal polymer hybrid is not only depending on adhesives performance but also strongly on the hot stamped steel’s coating performance. In this paper, the characteristics of hot stamped steel 22MnB5 Al-Si coating are investigated with regard to adhesion performance. Therefore, hot stamped specimens are manufactured under realistic industrial conditions investigating the influence of furnace temperature and dwell time on the overall coating and intermetallic layers of Al-Si coating. The specimens are investigated with respect to Al-Si coating thickness, lap shear strength of hybrid specimen and tensile strength of hot stamped steel demonstrating the dependency of the overall hybrid specimen performance from the coating performance.

Large-scale production technologies for hybrid structures are necessary to force lightweight design into automotive applications. The aim of today’s research is to find economic strategies for efficient manufacturing processes. This study adresses a process development for manufacturing instrinsic hybrid components using an in-mould infrared (IR) heating device [1]. The consisting concept of an integrated IR-radiator [1] has been developed to improve manufacturing processes for material hybrid components dominated by thermoplastic materials. This approach makes use of a substitution of steel with transparent ceramics at local areas of the mould and an the integration of IR-radiators. Thus, the problem of rapid temperature loss of thermoplastic preforms through direct contact to the cold mould surface can be avoided. This concept has been build up and comprehensive investigations of its usability has been made. The integration of a heating device enables a reduction of station times by utilizing dead times (interims) for heating processes. This also allows a gentle processing of material. The ceramic-faced surface of the preform can be heated up focussed to necessary processing temperatures at specific times. This research work discusses a process development using an in-mould IR heating device.

Economically feasible lightweight design represents an important objective for large-scale automobile production. According to the background of a high degree of lightweight design with sufficient cost-effectiveness, hybrid multi-material composites are increasingly getting into the focus of interest. In this case, composites and metals are combined to produce integrated components with optimized properties. These materials allow the creation of customized components. In addition, the component costs can be reduced by component-integrated functions. This reduction also allows a downstream of various process steps. [1] Due to their high lightweight potential, leaf springs offer a good opportunity for weight reduction in the vehicle. In heavy and light commercial vehicles, weight savings of up to 75% can be achieved for the leaf spring through the use of composites in comparison to conventional spring steel [2]. The variation of the spring rate in a limited design space is restricted for unidirectional (UD) composite laminates since each additional variant requires a new mold for manufacturing. The development of different variants has therefore only been achievable by the expense of increased tooling costs. However, composite leaf springs are not economically feasible for the use in a high variety and large-scale automobile production. So far, there are no suitable spring designs and production concepts for hybrid leaf springs. A high potential for specific variation of the spring rate is provided by adapted laminate architectures. With a hybrid laminate made from unidirectional fabrics and spring steel, a wide variation of spring rates with the same spring geometry can be implemented. Thus, many variants can be produced with one single mold. The challenge in manufacturing of a hybrid laminate lies in the process control. This process has to enable a complete wetting of the sheet steel insert and void-less infiltration of the reinforcing fibers. This study involves the systematic development and optimization of process arrangement for the manufacturing of hybrid laminates by means of vacuum infusion. The parameters influencing the process are fully determined and described. Their effects on the component quality are evaluated. The result of this study is a scalable strategy for vacuum infusion process of hybrid laminates at the high variant manufacturing of hybrid leaf springs. The solution method is divided into three steps. First, the basic physical and chemical effects and processes are characterized. Following, the materials are analyzed. This analysis focuses on the interaction of the materials with the infiltration-resin. This is supplemented by a discussion of the method for manufacturing a hybrid leaf springs using standardized specimens. For the methodological procedure, the setting parameters and results of vacuum infusion are determined and discussed. Based on the infiltration experiments, the effects of the variation of the setting parameters on the void-less infiltration are examined. Eventually, the results are discussed and processing recommendations are derived.

One promising approach to achieve automotive lightweight design is the intrinsic combination of metal and fibre reinforced plastics to hybrid parts. These parts can be manufactured by various methods such as injection moulding or thermoforming. However, the joining of the materials and their interface mechanisms remain a limiting factor to using both materials to their full potential. Therefore, it is necessary to develop new technologies to increase the structural integrity of hybrid parts. In this investigation, a load-oriented innovative interlocking concept by specifically designed mechanical undercuts on metal surfaces was developed. In this paper, ultimate loads of interlocking structure patterns were determined, both by a simulation model as well as by experimental investigations. As reference, conventional drill holes were used to create interlocking joints. Furthermore, the paper describes an approach to increase the ultimate load by variation of the structure pattern.

Automated production technologies of hybrid structures and components are one key requirement to force the way of lightweight constructions and design into automotive large-scale production. Furthermore, lightweight constructions need to provide additional functionality compared to conventional components to compensate for higher material and manufacturing costs. Therefore, the aim of today’s research is to find economic strategies for automated, function and process integrated final-shape-manufacturing processes. Conventional manufacturing processes for large-scale production are applied in sheet-metal working and plastics processing industries. For this reason, industry and science try to apply the process expertise of these industries on processing fibre-reinforced plastics (FRP). The combination of thermoforming of thermoplastic fibre-reinforced preforms (TP-FRP) with metal sheet inserts and efficient injection moulding processes shows a high industrial potential and at the same time the complexity of transferring the expertise of conventional to composite materials. The complexity occurs because of the differing material properties during the course of the process. The main challenge is the dynamic heat management of the TP-FRP during different process steps. For one thing, the preform must be molten and heated above melting point to perform a shaping process, an adhesive bonding with the injected material and the final consolidation. Conversely, a solidified preform has advantages in material handling and is less sensitive towards outside influences. Existing strategies of heating preforms during the process have several disadvantages. Either the preform must be overheated harmfully to balance the temperature losses or the process becomes inefficient because of the high thermal mass of the mould. Therefore, this paper introduces an integrative approach to apply an infrared (IR) heating device in a mould for processing TP-FRP with gentle and effective heating.