Keeping automotive insulation lightweight
Jim Griffin is managing director of Automotive Insulations, specialists in the design and manufacture of innovative noise reduction systems and thermal management solutions. In this revealing feature, Griffin explains how the choice of material and design can impact on insulation, especially when it comes to electric vehicles.
Nothing stands still in the automotive industry – manufacturers, designers and customers constantly demand lighter, quieter, more efficient parts – all at increasingly competitive prices. This means that those involved in automotive engineering need to constantly be looking forward, researching new technologies, equipment and materials if they are to give the client what they want.
Many UK based manufacturers have experienced an increased demand from European manufacturers for components that are lighter in weight. This has largely been driven by a combination of changing customer preference for smaller, more fuel efficient vehicles and stricter government led reduced emission regulations. Another significant contributory factor in the rising demand has been the extension in the range of electric vehicles available – and an increase in their acceptance and popularity amongst the general public.
However, new thinking is needed to make electric vehicles quieter. Whilst the popular perception is that they are silent, many users report a wide range of noises. Using an electric car on a day-to-day basis, it is possible to hear a change in performance more clearly than a measured result, as the constant change in driving speeds and environmental noises of everyday use are very hard to simulate.
Choosing the right material
Of course, the fundamental key to satisfying the demand for reduced volume and weight is using appropriate lightweight materials, combined with an optimum efficiency design. Using the right materials with the necessary sound absorbent properties will enable an engineer to take traditionally designed components, which are often based around molded shapes, and produce flat cut components that will take the shape of the body when fitted. Not only does this reduce weight, it also cuts costs and can speed up prototyping.
One material that is noted for its optimum performance, including excellent absorption within electric vehicle frequency ranges, is Xlite, a multiple layered, recyclable and weldable product specifically developed for electric, hybrid and lightweight vehicles. This material is typically used for interior trim including instrument panels, doors, pillars, headlinings and luggage sides and under-floor. It’s also suitable for engine bay and bulkhead insulation in combination with additional cover materials.
Xlite works through an impedance mismatch that provides an end result that is compatible to much heavier components. For example, it was used in a recent project for a Japanese OEM. This particular car maker took a vehicle that already had a low weight inner bulkhead insulation weighing approximately 2.8kg; however, material selection enabled a part to be offered that matched the performance for a 1kg weight saving. There are few areas in the car manufacturing process that can be cut by around one third at a stroke like this. In addition, the development of unique equipment complements the use of Xlite, enabling the edges of materials to be sealed and reducing the thickness in areas where packaging space is an issue or where the product is required to fold.
Challenging the design of components to ensure that the lightest material and the greatest material yield can be achieved is key to success. By working with design teams from the vehicle’s manufacturer, body panels can be designed to have less complex shapes. This enables the fitting of a lightweight flat cut component. The adaptability of these lightweight materials allows for localized additions of material where hot spot sound leakage issues are found. Furthermore, each product can be tuned to meet the specific frequency problems that have been identified by changing one or more layers.
Lightweight and absorbent
Another popular material choice is Thinsulate, a very lightweight acoustic absorption material produced by 3M. This material is so conformable that it can be used to drape over moldings as one part. Typically, on a boot side molding one would find three or four components in more traditional materials. This ability to drape reduces the fitting costs and inventory on hand at the assembling plant. By using this material, the components can be designed to be rectangular, as opposed to more complex shapes. These can then be used over several platforms by the same manufacturer. As a hydrophobic material, Thinsulate can be placed closer to a noise source - such as on the wet side of a door application.
In addition to their lightweight characteristics, both Xlite and Thinsulate have the added advantage of offering very good thermal properties. This ensures improved thermal management in a vehicle, reducing the need for further thermal materials. For example, air conditioning units can be smaller as these materials keep a vehicle warmer in cold weather and cooler in summer months. Loading on the power cell is thus reduced, improving the range.
The issues of emissions, economy and efficiency will only become more critical in vehicle design. Any future development must incorporate this need for sustainability with weight reduction a central part of the process. However, the consumer will not tolerate a reduction in performance and so the designer and manufacturer face a difficult task, best resolved by the careful selection of materials combined with clever component design to ensure that the integrity of both parts and performance is maintained.
About the author
Jim Griffin is MD of Automotive Insulations (www.autins.co.uk), a British company that specializes in the design and manufacture of acoustic and thermal insulation materials. Jim has over 22 years’ experience working in the automotive industry. The company has an extensive portfolio of international clients, including Bentley, Jaguar, 3M, and Land Rover.