In this article we explore the concept of the more-electric aircraft, the advantages and disadvantages that come with it, and the best silicone adhesives that can be used in their construction and maintenance.
What is the More-Electric Aircraft?
The More-Electric Aircraft (MEA) is an ongoing project in the aerospace industry which aims to replace all hydraulic, pneumatic and chemical power processes in an aircraft with electrical systems. Usually, many operations in an aircraft depend on these processes, such as air pressurization, power generation management, and flight control operations. However, considering the corrosiveness and flammability of hydraulic fluid, the difficulty of repairing and maintaining pneumatic systems, and the environmental damage caused by chemical emissions, it is clear that the avionics sector is waiting be revolutionized by an alternative approach such as the MEA.
Advantages of the More-Electric Aircraft
- Reduces total weight by removing hydraulic systems
- Easier maintenance through removing hydraulic systems
- Reduces fuel burn due to the lower weight
- Increases efficiency of aircraft
- More intelligent controllability of avionic systems
- Greatly reduces environmental impact
- Reduces noise pollution
Disadvantages of the More-Electric Aircraft
- Expensive to implement due to the new nature of the technologies
- Power converters required for all aircraft loads for power control
- Complex to fully integrate all electrical systems into one hub
- Electrical power losses will still have to be managed with care
- Battery assembly can often be complex without the correct expertise
Why Silicone Adhesives?
Silicone adhesives offer many benefits which make them perfect fits for use in the more-electric aircraft. A range of these benefits is listed below:
- Vibration/shock dampening
- Resistant to oils, fuels and water
- Non-flammable & thermally conductive versions available (UL94 V-0)
- Retain full flexibility from -115°C to 150°C, so can be used in the parts of the aircraft that drastically change temperature.
- High flexibility, therefore high movement capability
- Can be used in high flow for fast dispensing, but also in controlled flow for vertical surfaces. This means that they can be used as both encapsulants for fire protection, and as gap fillers for use in battery thermal management.
- Ideal for high-voltage insulation, retaining electrical insulation at high temperatures
- Low water absorption and therefore low risk of contact corrosion
- Unprimed adhesion to a variety of metallic and plastic substrates
DOWSIL™, traditionally known as Dow Corning, are proven experts in the field of silicone sealants, offering extremely reliable and durable adhesives that can be used in the aerospace sector. Their ranges of silicone sealants and adhesives are perfect choices for encapsulating sensitive electronic components by providing individual cell protection in the cases of a thermal event. Due to the low viscosity of the foams and encapsulants, very intricate geometries can be filled and protected as well (increasing the shelf life), while maintaining electrical insulation. DOWSIL™ also provide durable adhesives for assembling the numerous parts of a battery system together to be used in the MEA.
Adhesives, Encapsulants and Foams for Battery Assembly and Protection
DOWSIL 3-6548 RTV Silicone Foam is a two-part rubber foam which is great for sealing of fire rated penetrations containing cables and pipes. It is able to cure in 1.5 min (snap time) at room temperature, and also forms to complex and irregular shapes, ensuring maximal protection of components. Ensure that all joint surfaces are thoroughly cleaned and degreased to allow for optimal strength bonding. We recommend using the Wipemaster Wipe 9, a low-lint and low odour wipe, for this purpose.
DOWSIL EA-4700 CV is a two-part silicone adhesive that can cure in 2 hours at 25°C. It provides a controlled volatility, achieves strong adhesion within 24 hours, and is durable with many substrates. It also offers a 20 minute pot life and 150°C aging. Ensure that all surfaces are cleaned and degreased by a suitable solvent, such as a DOW OS fluid, for optimal strength bonding.
SYLGARD 170 Fast Cure Silicone Elastomer is a two-part encapsulant offered by DOWSIL™ which provides good flowability, flame resistance and rapid cure (12 min) at room temperature. It is a low viscosity elastomer and therefore can fill in narrow spaces and holes. Most silicone encapsulants require a primer for adhesion, therefore ensure that you ask for and check the Primer Selection Guide to choose a suitable primer.