Case Study Applications
The EIROS project will take technology from the laboratory environment and validate it in the extreme environments of the four case study components.
Wind Turbine Blade
The current state-of-the art for passive anti-icing solutions in wind turbine blades is to use a coating or paint to give the desired anti-icing properties. However the effect of these coatings is limited taking into account the ice conditions of the site. Thus, depending on the severity of cold climate conditions, the capabilities of passive systems may be not sufficient for properly improving wind turbine performance. Moreover, another limitation of the current state-of-the-art is the low performance against erosion of these coatings and the subsequent failure of the coating to provide ice protection once eroded.
- Wind turbine blade’s leading edge is the most important part in terms of aerodynamic properties. Due to the icing mechanism, it is also the most affected part of the blade due to ice accretion. Therefore there is a clear need in terms of avoiding or reducing ice accretion in that blade part. Currently, an active system based on heating-air is one of the most used solutions. Alternative systems such as direct fiber leading edge heating have to be discarded when taking into account lightning strikes especially in carbon fiber blades. Therefore, the use of anti-icing and high erosion resistance solutions in combination with this active system will improve the efficiency of the whole system with the corresponding AEP improvement.
- Nevertheless, decreasing ice accretion in other parts of the blade is also interesting in both aerodynamic and structural terms.
Moreover, more efficient solutions for protection against erosion are also necessary taking into account that this issue has an important negative effect on the blade´s aerodynamic especially in leading edge as in the previous case. Currently, high solids paints or tapes are used. However, high solids paints are not always enough to protect again erosion and tapes are usually not very easy to maintain (they also generate sound problems). Therefore, new, more efficient solutions are needed.
Aircraft Wing Leading Edge
The state-of-the-art for aerospace wing leading edges has many similarities with that of wind turbine blades; they have notably to be protected against erosion. Importantly, the formation of ice on the leading edge of wings represents a significant threat to the aerodynamic performance and therefore safety of the aircraft and so there are multiple systems in use to prevent loss of life. Ice accumulations (on the leading edge or upper surface of the wing) no thicker or rougher than a piece of coarse sandpaper can reduce lift by 30% and increase drag up to 40%. Larger accretions can reduce lift even more and can increase drag by 80% or more (Buck R, (year unknown)).
For this reason the EIROS material must work alongside existing passive and active systems used in ice prevention. Most anti/de-icing systems are active and many use pneumatic system (with hot air from engine) in a similar manner to wind turbine blades. Other active systems include electro-thermal (only used on one kind of long range aircraft), air heating, microwave, flexible boots, weeping systems and electro-impulse. Passive systems are also used and are primarily coating-based, using hydrophobic materials to prevent ice sticking to the leading edge; if ice does form it reduces the shear forces required to clear the ice from the blade. Other passive systems include black paint and chemical spray systems, although the latter has a “holdover time”, the time it remains effective. Additionally the chemical spray systems use glycol-based chemicals to de-ice aircraft and there are human health and environmental concerns with these chemicals.
- Full composite wing leading edge are a challenge: piccolo tubes cannot be used in Carbon Fibre-Reinforced Polymers (CFRP) leading edges, due to the low thermal conductivity of the material used; therefore new solutions have to be found to replace this system completely. The use of electro-thermic anti/de-icing systems is under investigation. But Wing Ice Protection Systems (WIPS) combined with a passive solution have the potential to be much more efficient.
- The wing area, situated stream downwards of the leading edge EoP, is not equipped with WIPS. In the most demanding cases, this requires full evaporative anti-icing working modes to avoid runback ice to accrete in these areas, by evaporating the droplets upon impact. Maintaining a full evaporative working mode in front of the leading edge requires high energy levels.
- Furthermore, there is a need for an efficient protection against erosion which has at least the same performance as BR 127 primer, which works well on an anodized aluminium surface due to the porosity, but not on a CFRP surface. And a mono-functional erosion resistant surface will not reduce the necessary energy for WIPS however.
- For metallic wing leading edges full evaporative anti-icing working modes are used for the most demanding cases, which require energy levels of up to 5 kW/m(span).
EIROS offers an improvement over current coating technology which suffers from similar erosion problems as wind turbine blades. Additionally, the property improvements offered by EIROS differentiate it from other solutions. As a bulk composite material it can be substituted for current composite materials (pending approval) with minimal impact on current passive or active de/anti-icing systems.
CRYOGENIC STORAGE TANK
Current cryogenic tanks used in the space industry are conventionally made from metallic materials, generally from 7000 or 2000 series Aluminium alloys, depending on the cryogenic medium within the tank. 7000 series are preferred for liquid hydrogen, whereas 2000 series are used for storing liquid oxygen. The main drawback of metallic tanks is the high weight, especially due to the need of heavy insulation materials that are used to insulate the tank from ambient temperatures. Weight savings in launch vehicles greatly reduces cost and is one of the most important factors in vehicle design.
Composite cryogenic tanks can be manufactured via different routes as well. Filament winding is the conventional way of producing composite pressure vessels. In the EIROS Project, composite cryogenic tanks will be manufactured via two different approaches; wet winding and prepreg placement.
- In the first approach, carbon fiber tows will be used as the reinforcement, and nano-enhanced epoxy resin that will be developed through the EIROS project will be used as the matrix material. Nano-enhanced epoxy resin will bring anti-icing, self-healing and increased toughness properties to composite cryogenic tanks.
- In the second approach, carbon prepreg tapes which contain nano-enhanced epoxy resin as the matrix will be used to manufacture the composite tanks. With these two approaches, different integration techniques of nano-particles to the bulk composite will be studied and compared.
In general, composite materials have huge weight saving advantage over metallic materials due to their high specific strength; also, in metal cryogenic tanks, due to icing problems, heavy insulations are used to isolate the part from ambient conditions. With the use of the technology output of EIROS Project, structural composite tanks will be ice resistant, hence will eliminate the need for additional heavy insulation materials that present a huge drawback for metal counterparts. All in all, the overall weight of launch vehicles can be significantly reduced via replacement of metal tanks with composite tanks. In launch vehicle design, weight is one the most important factors, which greatly reduces cost. Additionally, nano-enhanced epoxy resin developed within the Project may also result in toughness increase, which in turn inhibits crack initiation and propagation at cryogenic temperatures. With taking this into consideration, the new material developed in EIROS Project can lead to the development of reusable cryogenic tanks, which is especially important for the future of Reusable Launch Vehicles (RLV).
Automotive Components – Bumper Trims & Oil Pans
Bumper trim components are assembled onto the front and rear bumpers, and they must withstand all the low energy impacts that bumpers must absorb without breaking, but they also have high requirements regarding the abrasion and scratch resistances due to their location in the vehicle. It is a part that protects the bumper or its environment from any surface damage by suffering all the damage itself; the most typical damage is when the driver rubs the car against a column when parking, damaging these parts. For this component, self-healing is the most interesting functionality.
The majority of oil pans for transportation are made in steel using a hot stamping process and subsequently painted to avoid corrosion (due to the exposure to the elements). A new generation of oil pans made by injection moulding of thermoplastic polymers (eg. Polyamide 66 + glass fiber) is becoming increasingly common in vehicle production. Replacing the steel oil pan with a polymer one saves weight and cost. Reducing weight is a key strategy in meeting EU directives on CO2 emissions. The use of thermoplastic polymers makes the oil pan more susceptible to fracture due to the impact and abrasion with stones or other accidental impact with bumps or ice/snow (in winter). In addition, the polymer has to guarantee good performances at very high temperature (inside) in an aggressive environment due to the oil at high temperature and at very low temperature (outside) in winter.
The Eiros technology can be used to improve mechanical and thermal properties of epoxy resin to realize oil pans in composite. In this way, the use of composite to replace steel becomes viable and achieves an important weight saving. The Eiros technology compared to plastic oil pans can help to simplify the current design and to reduce the thickness of oil pan necessary to guarantee a good impact and abrasion performances. Moreover with improved thermal and chemical properties it will be possible to use a composite oil pan at the highest and lowest range of temperatures.