On the road to a greener future with composite materials
Francis Arthur
Composite materials have significant potential in the transportation industry, making it possible to create lighter parts for cars, trains and aircrafts but, until recently, the cost and time often associated with composite material production has made high-volume manufacturing of composites unsuitable for many industries. This article discusses an automated manufacturing process that makes it possible to produce these lightweight materials on a large scale, reducing vehicle weight and, therefore, fuel and energy usage, contributing to sustainable transport initiatives.
The future looks light
Use of lightweight materials in the transportation industry has typically focused on aluminium due to its strength, widespread availability and cost-effectiveness. However, composites demonstrate comparable strength while reducing weight by up to 40%, as well as being chemical resistant, durable and low maintenance. Their flexibility also feeds into intelligent design and shaping that allows structures to be further streamlined. For example, thickness can be varied between low- and high-stress zones as necessary, moulding the individual components to the specific application and shaving off extra weight in the process. Composite materials also offer the ability to form large parts from a single piece, increasing strength and minimising the risk of failure, further adding to their growing popularity.
Composites can be made from a variety of substrates ‒ such as glass, carbon, aramid, flax and hemp – and the manufacturing process consists of multiple different resin systems, including epoxy-based, snap cure, high-temperature cyanate esters and bio resins. This variety produces a range of qualities, making these materials incredibly versatile and allowing each project to be tailored to detailed design specifications. For instance, glass fibre has a degree of spring deformation and higher true failure strength than aluminium, so that it can resist continual impacts and variable loading.
Aerospace has long benefitted from this kind of flexibility, and simultaneously taken advantage of the light weight of composite parts to reduce aircraft weight, with each kilogram shed resulting in fuel savings, and this has paved the way for other industries to follow. The rail industry is now also beginning to take this approach to trim down the weight of a fleet of trains, equating to significant daily energy savings, reducing costs and getting rail transport on track to a more eco-friendly operation.
Breaking down the barriers
The laborious manufacturing process has long been a significant barrier to many companies looking to adopt composites, and so the challenge now is to make these solutions more widely available to a greater range of industries. Traditional production methods usually require a hand lay-up and autoclave curing, which entails a significant level of skilled labour, and single parts can often take hours or days to create, on top of significant R&D time. These limitations greatly add to the total time and financial costs further down the line, resulting in an unavoidable choice between high product quality or high throughput. However, programmable robotics and advancements in material science – such as snap-cure resins – have transformed this largely manual process into a fully automated workflow. Such an innovation is finally making high-volume, high-quality composite production a reality.
One of these novel automated manufacturing techniques combines snap-cure resins and prepreg materials with cutting-edge robotics, reducing the time it takes to form composite parts from hours to just a few minutes. Automation has been incorporated into every production step, beginning with prepreg fabrication with machined ply cutting and an innovative system called Fast Press Cure (FPC), which presses and cures the material in a fraction of the time previously required for thermosetting materials. The prepreg component is formed to the desired shape and rapidly cured, before being automatically de-moulded, removed and passed on to final machining and finishing operations. Each parameter of this process has been thoroughly optimised, ensuring both a high-speed process and high-quality end products. Another benefit of automation is the elimination of human error with reliably precise alignment, pressure and temperature, which further contributes to the consistent generation of high-spec composite parts.
A driver of change
Electric vehicles are yet another application in the transportation industry where lightweight composites have an advantage over traditional steel components, and where small changes could make a huge difference for sustainability goals. Electric car batteries significantly add to the overall weight of the vehicle, but this innovative process is already being employed to make lightweight battery boxes. These new casings are strong, rigid and impermeable, and contain 60 aluminium pins – added after the machining phase – making up one half of the mounting design, as well as 15 aluminium screw plates for the structural mounting of the composite base panel to the framework. The pins secure the battery modules and create a gap to allow packaging space for the liquid cooling plate that resides under the battery modules.
Electric vehicle batteries must also contain an air gap or non-conductive layer to avoid the risk of arcing, and this inefficient use of space can be solved with non-conductive composites – such as glass fibre – that can rest tightly against the battery without requiring a spark gap for electrical isolation, making them a space-saving option. All of these manufacturing steps are pre-programmed and automatically performed by the state-of-the-art robotic production line, resulting in a fully functional product that is ready for post-manufacturing modifications.
On the road to sustainable travel
With this streamlined, efficient and cost-effective manufacturing technique, high volume applications can finally take advantage of the strength and light weight of composites, and the stigma that composites are only suited to low volume, high price applications should soon become a thing of the past. Light weighting is just one way that innovative composite constructions are changing the future of electric vehicle designs, and the automotive industry as a whole. The introduction of bio-based resins is also helping to further reduce the industry’s reliability on chemicals which can be detrimental to our health and the environment, ultimately bringing the transport sector one step closer to achieving its sustainability goals.
Francis Arthur, Engineering Manager, TRB Lightweight Structures
