Klaus Dröder’s research while affiliated with Technische Universität Braunschweig and other places

Hybrid materials enable innovative and technologically advantageous lightweight design solutions, especially the efficient combination of metals and polymers is a promising approach. This contribution addresses an additive manufacturing (AM) process with polymers on the surface of foamable extruded aluminium profiles. The aim is to individualise aluminium profiles with locally applied polymer components using the foam structure as a mechanical bonding interface. The bond strength of hybrid aluminium foam-polymer composites fabricated via screw extrusion additive manufacturing (SEAM) is investigated and the influence of the key process parameters as well as the properties of the aluminium foam structures are taken into account. Additionally, X-ray microscopy is used to analyse the pore structure, evaluating the pore size distribution, the wall thickness, and the pore filling. The material- and process-dependent bond strength is determined from lap-shear and cross-tension tests. A ductile failure of the specimens was detected, which is caused by mixed failure modes such as cohesive failure and adhesive failure in the polymer and in the aluminum. By minimising the distance between the extruder nozzle and the aluminium foam, the samples with the highest adhesive strength of 5.4 MPa in the cross-tensile test and 7 MPa in the lap-shear test were produced. An inhomogeneous pore distribution shows the highest influence on the tested bond strength, which results in a large scattering of the maximum detected testing force. The aluminium foam-polymer composites show potential for overcoming the problem of joining dissimilar materials to produce hybrid structural components, which could enable further advances for these types of components.

Lithium-ion batteries (LIBs) immensely contribute to the electromobility’s success for achieving climate change goals. As LIBs are forecasted to succumb to optimization limits in the coming decade, next generation battery technologies, such as all-solid-state batteries (ASSBs), gain noteworthy attention for meeting ever-increasing cell performance requirements. By deploying solid electrolytes (SEs), compared to liquid electrolytes in current LIBs, ASSBs benefit from enhanced safety against flammability and allow for the usage of lithium metal anodes for higher energy densities. Here, polymer solid electrolytes, such Polyethylene oxide (PEO), are widely used for their high flexibility and hence beneficial processability properties compared other SEs. However, their adhesive behavior poses challenges when conducting handling and stacking processes with conventional grippers during cell assembly. In this research, we present a parameter study on ASSB handling and stacking with PEO-based cell components aiming to promote process understanding and point out optimization potentials. An experimental design for testing different grippers is devised by which deposition accuracy is systematically assessed in relation to the holding force, gripper speed, and placement distance. Within this evaluation, the electrostatic gripper with a Polytetrafluoroethylene (PTFE) dielectric provides adequate position and orientation accuracies in almost all experiments while showing improved accuracies with higher holding forces. Parameter settings achieving higher overall deposition accuracies for all tested grippers are identified. This research provides insights into the establishment of stacking processes for realizing an industry-scale ASSB production.

Granular grippers are a promising approach to the flexible handling in soft robotics. As a result of the used granular materials, these grippers can grasp a wide spectrum of objects with many different shapes, especially compared to conventional mechanical or suction cup grippers. However, accurately predicting the graspability of differently shaped objects remains a challenge. Additionally, a comprehensive understanding of the various influences within the grasping mechanism is still lacking. Therefore, a specific granular-based gripper combining the principles of jamming and vacuum grippers was previously experimentally investigated for different object shapes, while varying various design parameters. In this study, the previous work is expanded through numerically modelling this specific gripper. For this purpose, the first sequence of the grasping process (moulding process) is modelled using the discrete element method, while the bonded particle method is used to model the membrane behaviour. The simulation shows good agreement with the experimental moulding results of differently shaped objects through optical comparisons. Furthermore, the parameters characterising the moulding are compared with a previously introduced object characteristic parameter, enabling the identification and characterisation of influences within the grasping mechanism.

The recycling of retired lithium-ion batteries (LIBs) involves typically pretreatments such as discharging, disassembly, shredding, separation, followed by pyrometallurgical or hydrometallurgical processes to recover active materials. These processes face substantial challenges in efficiently separating materials and achieving high purity levels. This research focuses on conceptualizing a framework for developing automated battery disassembly process chains. Utilizing computed tomography (CT) scans, internal cell structures and joints are identified, contributing to the development of disassembly procedures. Through post-mortem analysis, cells are manually disassembled and the processes are evaluated, facilitating the establishment of the framework for automated disassembly. Key parameters are outlined and potential tools along with methods for further studies are summarized. A disassembly station derived from the framework is established, demonstrating automated disassembly processes with a 13.88 % increase in efficiency compared to the manual approach. This study contributes to advancing automated disassembly processes, enhancing an efficient recycling of LIBs through improved materials separation in pretreatments.

This study focused on evaluating the mechanical, thermal, and morphological properties of recycled polyethylene terephthalate (RPET) hybrid mineral-filled composites containing fine acicular wollastonite, mica phlogopite, and talc platelets. Depending on the filler content, both single mineral-filled composites as well as hybrid mineral–filler composites were investigated. The maximum nominal filler content was set to 20% by weight with varying ratios for combinations of the wollastonite–mica and wollastonite–talc composites, respectively. Aside from the tensile, compression, and flexural properties, the heat distortion temperature and degree of crystallinity were carried out. Moreover, the dynamical response of the hybrid mineral-filled composites on different frequencies (1 Hz, 2 Hz, 5 Hz, and 10 Hz) was considered. By using scanning electron microscope photography, the fracture surface and the morphology of the composite material were observed. The results demonstrated enhanced stiffness, strengths, and thermal stability for all hybrid mineral-filled composites. In particular, the wollastonite–talc-filled RPET composites revealed a good compatibility and showed the most beneficial results.

Supply chains for cities are currently challenged due to geopolitical conflicts and general resource scarcity of substantial raw materials. One currently discussed strategy to reduce the dependency of external supply is a relocalization of production facilities to cities enabling local secondary raw material extraction integrated in Circular Economy value creation chains. Urban regions offer the potential for the installation of circular and secondary raw material factories because of the concentration of waste-and byproducts, which can reduce transport efforts. The installation of urban factories is however highly dependent on the economic feasibility as well as the acceptance of the local environment. One critical source for the retrieval of critical raw materials are e-wastes. The current retrieval of these critical raw materials from e-wastes is connected to high spatial requirements and production volumes. These characteristics would hamper an installation in urban areas. Current literature provides different approaches with the intention to adapt e-waste treatment to these special conditions. To assess which of these are suitable for utilization in urban environments, this paper provides an analysis of their possibility to generate an urban fit. To do so, criteria containing ecologic, social, and economic, technological indicators are defined and an assessment of the suitability is conducted.

The production of lithium-ion battery cells (LIBs) for electric vehicles requires a considerable amount of energy and raw materials. Due to the increasing added value along the production chain, it is essential to recognise deviations in the intermediate products as early as possible using 100% inline measurement processes. For this reason, LIBs are inspected during cell assembly using plain radiography to qualitatively check their internal geometry. For safety-critical features, such as the anode-cathode-overhang (AC-overhang) in the composite, measuring methods are required that are not fulfilled by plain radiography. The use of computer tomography (CT) offers a solution for this demand. However, to realise a 100% CT inspection, the scan time of conventional systems and the number of applications along the cell assembly must be reduced. This research presents an approach to overcome this limitation in the form of a cross-process X-ray inspection strategy based on a technical and economic analysis of the cell assembly. To reduce scan time and the number of X-ray applications, multiple internal features are measured in a single CT scan prior to electrolyte filling. An initial feasibility assessment of this inspection position is being investigated using a state-of-the-art metal-jet tube and photon counting detector. This provides an inspection time of 1 s, enabling detailed inspection to be combined in a time-efficient process. However, moving the CT inspection downstream would contradict the key objective of early defect detection. To overcome these challenges, an upstream vision system was developed. This vision system detects outliers immediately after the stacking process by detecting the position of the external feature separator in the electrode separator composite (ESC) without X-rays and at a much lower cost than CT. This approach aligns with the primary objective of early defect detection in the production chain through the cross-process inspection strategy.

Thermoforming enables the efficient processing of continuous fibre reinforced thermoplastic (CFRT) such as organo sheets into geometrically complex and structurally advantageous structures; however, resulting components are often hybrized through additional processes for an increased rigidity. For this, injection moulding is a widespread option, as it allows for the precise integration of plastic ribs into the thermoformed products, leading to improved structural integrity and mechanical stiffness [1, 2]. As thermoforming and injection moulding offer synergistic advantages, especially based on many related process steps, the processes can be successfully integrated [3]. When further manufacturing steps such as cutting are combined within this integrated process, the previously required handling steps are avoided entirely and the overall process cycle time can be reduced [4]. Within the present research, the integration of multiple process steps into an integrative process chain is examined through a prototypical experimental setup. The investigated one-shot injection moulding mould (IMM) combines the thermoforming and trimming of the final contour as well as the injection moulding step within an index plate mould. This enables comparably short process cycles while maintaining part quality, such as the defined position of CFRT in edge contours. The process chain is validated and resulting demonstrator components are analyzed regarding the adhesion between CFRT and applied thermoplastics by applying tensile loads. Even in comparison to conventionally established processes, the investigated integrated process chain enables feasible results. Within the examined process parameters, the temperatures within the different system components significantly influence the overall part quality. Overall, the concept for an integrated process chain shows promise for further investigations, as it offers significant gains in overall process efficiencies through reduced handling steps and potential time savings.

Artificial Intelligence (AI) offers promising capabilities for many industrial applications and the use of AI has gained traction within manufacturing processes. However, working procedures lack criteria to decide about the benefit of AI systems for particular use cases and do not describe any uncertainty analysis in the development stage, since they assume readily available significant data. The objective of the present study is to introduce a process model, which includes decision criteria to determine the necessity of AI and evaluate the uncertainty of the system, consisting of suitable sensors and algorithms, in early development phases. The procedure is verified by analyzing a battery production line and identifying the prediction of success for MIG-welding as a suitable point of improvement by an AI system. A qualitative extraction of domain knowledge and data source selection leads to a fuzzy model and a clear distinction between the epistemic and aleatoric uncertainty of the system to estimate the prediction capability. The presented method allows the distinction between such uncertainties in a systematic development process and thus allows for a targeted optimization of AI systems. Extending the introduced systematic to other industrial fields can help to increase the implementation rates of AI in manufacturing.