38 September/October 2025 | E-Mobility Engineering and associated costs. For example, thermoplastics can achieve tight radii and intricate contours that are difficult or impossible to replicate with metal stamping or machining. Additionally, thermoplastics are non-corroding, which enhances the longevity of battery enclosures and reduces maintenance needs. Their inherent electrical and thermal insulation properties also contribute to safer battery designs by minimising the risk of short circuits and thermal runaway. From a sustainability perspective, thermoplastics support a reduced CO2 footprint through lighter weight and recyclability. Many formulations are compatible with closed-loop recycling systems, aligning with broader environmental goals and regulations. Thermoplastics also enable fast cycle times – often under 120 seconds – and high-volume production within a lean manufacturing footprint. This makes such materials suitable for scalable automotive applications where speed, efficiency and repeatability are essential. Material selection The selection of PP or PA resins for enclosure material is derived from a system-level approach that must balance structural and functional performance, material availability, global supply, CO2 footprint and system cost. In many cases, the resins are supplemented with up to 50% glass fibre to provide a robust material for battery enclosure design. One of the key benefits of composites is the ability to integrate components during the one-step moulding process to address areas of high structural loading. Endless or continuous glass fibre profiles can be integrated as local reinforcements. During the moulding process, these profiles are heated to melting temperature and placed within the mould, creating a bond with the base resin material. Glass fibre plays a crucial role in enhancing the structural integrity and performance of battery enclosures without compromising on cost and sustainability for high-volume automotive applications. At the same time, glass fibre improves the thermal stability, particularly in the case of thermal runaway events. Extensive thermal runaway testing of the materials includes a variety of cells and cell formats with characterisation of specific cell thermal runaway events, including temperature, pressure and gas composition. These data ensure that thermoplastic material systems can meet and exceed legal and customer requirements for thermal runaway protection. The process of evaluating the materials with the various additives includes quasistatic and dynamic coupon level tests, including failure calibration, to develop basic material ‘cards’. To ensure good correlation at a full system level and achieve the highest material card level, called ML6, systemlevel testing with both quasistatic and dynamic loads, including failure calibration, is necessary. Use of composite material not only has to consider strength but also other factors. Electromagnetic shielding capability is typically lacking in composites, but multiple additives have been developed that can be integrated into the moulding process or assembled in downline processes. One in-mould example is an aluminium film that can be draped within the mould and formed/moulded to the final shape. Solutions like this have been tested to meet typical automotive electromagnetic interference (EMI) standards such as CISPR A4. IM versus CM The choice between injection moulding (IM) and compression moulding (CM) depends on specific project requirements and whether there are impact requirements such as bottom bollard, vehicle crash and crush. The integration of steel and aluminium sheets, strips and beams is possible and already in use in mass production applications today. This makes the designs highly customisable to specific requirements while providing a sustainability advantage because the carbon footprint of the base material is over half that of aluminium, and it is significantly lighter A battery case in thermoplastic (Image courtesy Kautex Textron)
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