At the recent JEC World exhibition held in Paris, Henkel unveiled its portfolio of high impact products for the aerospace industry, including structural adhesives comprising film and pastes, lightweight surfacing films, primer and surface treatment solutions for composite and metal applications across the aerospace industry.
With weight saving being a fundamental driver within the aerospace industry, Henkel showcased its lightweight Loctite EA 9845 SF Aero surfacing film. Claimed to offer up to 30% weight savings compared to existing surfacing films, it provides a reduction in manufacturing process time by minimising pre-paint preparations.
The film can be co-cured at 120 or 177°C, is said to provide excellent surface finish and is capable to be processed out-of-autoclave. It protects the underlying composite materials, and has enhanced UV and paint stripper resistance.
Lightning and lightening
Along with lightweighting, lightning strike protection is also vital in supporting aerospace industry demands. Loctite EA 9845LC Aero, based on Loctite EA 9845SF Aero surfacing film, provides the same high quality surface finishing, but also incorporates lightning strike protection. This film includes lightweight, expanded copper or aluminium mesh for maximum electrical conductivity and protection of aircraft composite parts.
The use of an integrated lightning strike solution reduces the number of materials to be inventoried and provides a manufacturing cost reduction. Loctite EA 9845LC Aero lightning strike film is available in a variety of area weights to meet the requirements of different lightning strike zones on the aircraft.
“The composite materials market is growing and the industry is ramping up massively,” begins Henkel’s global key account manager, aerospace, Guido Adolph. “The challenges mean reducing cycle times to produce parts faster. It sounds easy but it’s not, especially when you think about the whole process that involves the specification of adhesive products for the aerospace sector.
“What we are showcasing at JEC are the different target areas, and one of the main ones is an aerospace surfacing film, Loctite 9845 where we have two different types of configurations in terms of standard surfacing films and surfacing films, plus lightning strike properties. Because of its composition and the combination of the resin and the matrix, this surfacing film is about 30% less in weight than traditional ones. This brings customers the advantages of less weight and at the same time, the preparation of the surface itself after the process, and because it is painted, the quality of the surface is therefore in very good shape.
“Customers can cure Loctite 9845 within two different temperature areas: 120 or 177°C. Out-of-autoclave is also possible. They can also cure it at room temperature too, but they will need to understand that at room temperature, the time for the final curing will be longer. At the temperatures I’ve mentioned, it will take between 2 hours and 1.5 hours.
Feels good to me
I’m interested to know whether Loctite 9845 can help level out the peaks and troughs of the surface. Adolph compares it to an orange peel which has minute uneven areas.
“A surfacing film cannot reach say, a depth of couple of millimetre, but to repair and to reduce the amount of the first layer coating of filler - before you apply the top coat, our surfacing film is an important step because it reduces the amount of sanding. Normally, a filler would be applied, but if the surface quality is already in good shape then you can reduce the production time greatly. Then there is the different configurations of aluminium and copper in terms of lightning strike protection. Some of the large aerospace OEMs prefer aluminium, while others prefer copper, so we have both configurations available with different aerial weights, depending on zone where they apply the film. This is because they have to be very selective where they apply the film and avoid areas where it is not needed, otherwise it adds weight.”
Henkel’s Loctite 9845 surfacing film is supplied on a 30inch roll. Adolph advises that in terms of the pattern and mould design, application of the surfacing film needs to be thoroughly checked. For example, if the customer is applying it to some really critical areas, i.e. sharp edges and curves, then they will need to ensure – particularly for lightning strike protection that contains a mesh - that they correctly prepare the application of the film.
It’s a material world
In terms of industry trends, Henkel is addressing the issues of saving the customer time and the desires for multi-material bonding and adhesion properties.
“I’m not saying it was easier, but in the past, the industry relied on aluminium aerostructures and different types of alloys whereas today, it’s common to have hybrids of both composite and aluminium, and different types of prepreg; it is a real mix. Our products need to be connecting efficiently to all these different types of materials that behave in different ways.
“We also see a tendency that shimming is still required, but to fill gaps where there are material variations of a couple of millimetre on a wing skin, customers prefer to avoid using different shim materials and multiple steps and instead simply shim to the full thickness required. Therefore, today’s demands are clearly about multi-material combinations, time-savings, one-hit applications and avoiding lengthy curing cycles.”
From the company’s perspective, Adolph believes it can serve the full value chain, and for the surface preparation requirements of the aerospace sector, it literally has all the configurations for materials covered!
“Our customers can now enjoy a complete turnkey solution,” he concludes. “Few companies are able to deliver the kind of package we offer. As the largest global adhesives company, we focus on adhesives and it doesn’t matter whether we’re dealing with the automotive or electronics industry, we have products in our portfolio that we can leverage on, so that they are attractive for the aerospace industry too. Our decades of experience in other industries can be transferred to the aerospace sector.”