Automotive

With the EV market growing at a rapid pace thanks to the drive for more sustainable means of travel, alternative fastening techniques for this sector are becoming increasingly necessary. bigHead is playing a significant role in supporting Bossard’s Global Electric Vehicle EV Group which concentrates on the component fastening requirements of electric vehicle designers and manufacturers across Bossard’s worldwide marketplace.

EVs moving into mass production

The Global EV Group of Bossard met recently in Austria to address electric vehicle manufacturing, with bigHead fronting the discussions related to fastening techniques for composite materials. Composites now play an ever-increasing role in the manufacture of EVs, presenting a range of fastening challenges, in which bigHead states it has great experience and knowledge.

From bigHead’s innovation team based at Cranfield, Oli le Marquand Brown was the representative at this gathering. With increasing numbers of EV models moving into mass production, this creates a growing emphasis on maximising cost efficiency and production rates. Enabling swift and accurate fastening within large automated systems becomes critical. “In finding solutions, the bigHead team considers the entire production process from design to final assembly and has the breadth of knowledge required to discuss solutions with engineers in all of these fields,” states bigHead. 

Composite materials have many structural benefits for EVs 

Composite materials have several advantages that can be exploited when utilised in electric vehicle applications. The most widely publicised of these being the excellent mechanical properties and low density possessed by such materials, making it possible to produce incredibly lightweight structures. A lighter vehicle uses less energy and subsequently has lower carbon emissions per kilometre, whilst the driving range is also increased. Various forms of composite materials are being used for an increasing range of vehicle components. In the past, the high cost of using composite materials restricted their use to low volume and high performance vehicles.

However, reduced costs are becoming apparent as composite suppliers are integrated into automotive supply chains. This, along with the potential for simplified assembly operations due to reduced overall component numbers and increased modularity compared to metallic structures, means composite materials are an increasingly attractive proposition for use in high-volume vehicles.

Battery housing

EV batteries and battery housings are heavy components – often weighing over 400kg and weight reduction is facilitated using composite materials for the battery enclosures. Composites also ensure safety of the battery system is maintained – additives within the polymer matrix ensure these composites meet stringent toxicity and flame retardancy requirements, reducing risk of thermal runaway, whilst polymeric composites are also electrically insulating, reducing the risk of short circuiting. Furthermore, composite materials are known for their corrosion resistance, eliminating the requirement for additional coating processes. This helps reduce overall production costs and the carbon footprint associated with the battery housing assembly.

Electric motor

EV motors also account for a good deal of vehicle weight. Composites are being developed that are suitable for the rotor housing, stator and other components in electric motors. It has been shown that introducing composites into electric drivetrains will reduce their weight at the same time as improving the efficiency of the drive systems. Composites can also be used in the metal rotor shaft. The laminated magnet carrier can be replaced with an injection moulded part with functional separation of the torque transmission and the magnetically active part.

The metal rotor shaft can weigh almost 30% of the total rotor weight and the laminated magnet carrier around 60% so reducing the weight of these parts has significant benefits.

Understanding and solving composite fastening challenges 

As composite materials grow both in range and volume of applications, the challenge to find the right fastening solution increases.

“When customers move from metal to composites, as a consequence of light-weighting or for reasons of performance or design enhancement, they discover a lack of guidance or knowledge in fastening composites,” bigHead explains. “This can be a major hurdle and lead to compromises and inefficiency, whether at the design, manufacture, or final assembly stage. There is no time in these environments to experiment and try things out, but bigHead can provide the clarity and guidance required. We speak our customers’ language of composites and also provide a bridge to the world of fastening where the available support and expertise is sometimes more aligned to metallic or non-composite materials.”

bigHead support for EV composite fastening

Bulkhead design 

“bigHead has provided valuable design and assembly advice in fastening for the production of the lightweight composite bulkhead for the latest model from a well-known USA electric vehicle manufacturer,” highlights the company. “Finding the optimum way to embed the bigHead, by including it within the bulkhead forming process, eliminated the need to spend time and money on secondary fastener installation operations. Integrating the bigHead fastener into the bulkhead manufacturing process ensured the fastener locations aligned exactly with the global component geometry and enabled an increase in the manufacturing through-put of the bulkhead. Requirements in this sector have been growing rapidly in recent years and we have the capacity to meet this demand as it develops.”

Working with SMC

Sheet moulding compound (SMC) is being increasingly used in numerous electric vehicle applications. Working alongside the Cranfield Composites Centre at Cranfield University, bigHead have produced a demonstration mould tool showcasing how bigHead fasteners can be easily and reliably embedded into SMC, without any ingress of resin into or around the fixing – a known issue when integrating fasteners into SMC. Fasteners can be incorporated into the SMC compression moulding process without any change to the moulding parameters or process cycle time.