Filling the gap

Henkel was on hand to showcase its new Loctite EA 9378 AERO, an innovative next-generation epoxy-based liquid shim material at JEC World. Still under development, Mike Richardson joined with the Henkel team to learn more.

When it comes to assembling large aerostructures, it’s inevitable that there are going to be some gaps appearing between the joins. This is due partly to slight discrepancies in dimensional inaccuracies on the larger dimensions of specific components. So, how do we fill these gaps?

In a perfect world no-one wants a gap, but when you’re dealing with rib-to-skin dimensions across some huge structures, then these gaps tend to become more visible. OEM airframers use solid shims in the form of metal and plastic plates that have the same function, but they are really designed for specific gap widths. Liquid shim materials fit in areas where there is the freedom to go up to gaps of 3mm.

To meet these gap-filling demands, the aerospace sector relies on strong partners capable of meeting its growing demands for more efficient and lightweighting materials. Among the highlights on Henkel’s exhibition stand during the JEC World held in Paris last March, was its Loctite EA 9378 AERO, an innovative next-generation liquid shim material under development.

As a gap filler for use as an integral component in primary aerospace structures, the new grade is said to build on the proven weight and fuel saving benefits of Henkel’s broad existing portfolio of Loctite liquid shim solutions, while offering even faster curing rates at ambient temperature. The material will be aimed at helping aerospace OEMs reduce both carbon emissions and manufacturing costs in a wide range of consolidated structural designs.

Building bridges

Loctite EA 9378 AERO has been designed for structural gap filling and tolerance bridging with uniform stress distribution throughout assemblies. It exhibits controlled flow characteristics and will fill even large gaps up to 3mm with good slump resistance, which gives designers more flexibility in compensating part tolerances. Besides rapid curing, the new liquid shim material also offers high mechanical strength in combination with enhanced fatigue and thermal cycling resistance. Currently in its scale-up phase, the product is being sampled in the field and has already received positive feedback from selected customers.

“Our broad focus comprises aligning our products better with automated dispensing solutions and improving production time-saving processes,” begins Guido Adolph, Henkel’s global key account manager, aerospace. “There is a trend for ongoing hybrid systems that require a solution for a combination of both composite and traditional metals, so whilst gap-filling properties are still an important topic, saving time is increasingly becoming the main driver because aircraft build rates are increasing. Henkel’s Loctite fits in the range where a high gap fill and a fast cure are required.

“In addition, temperature resistance is also important when using gap-filling materials in applications where areas of the aircraft are more temperature-sensitive than others, so with Loctite EA 9378 AERO, our customers can now move into areas where higher temperatures up to 120°C take place. Most of the materials in the market are only suitable up to around 80°C, so this is really something that can offer more stability and freedom to apply it in other areas.”

The application of gap-filling materials normally involves a manual production process, but with the previously mentioned build rates continuing to soar skywards, this process is crying out to be automated. Consistency and repeatability of performing the process also stand to benefit hugely too.

“If I was to say that in the next 20 years, the need for automated dispensing will double because of increasing build rates, potentially the industry will not reach this target with the existing amount of manual-based dispensing. This is forcing a demand for more automated dispensing equipment in other manufacturing processes.

“To improve repeatability, automated dispensing can guarantee the dosing amount exactly required, each time – every time. It also enables our customers to be more precise with the material when in use. Obviously, we want to sell more adhesives, and this is the ultimate target, but automated dispensing will certainly improve the business case on the areas of the gap being filled, the repeatability and the quality too. Our aim is for our products to be adaptable for automated dispensing equipment so that we can offer the full package of this fast-curing liquid shim, plus the dispensing equipment.”

Spain gains ground

Henkel recently announced that it is expanding its European production facilities at Montornès del Vallès, Spain to maintain a continued focus on innovative solutions designed to enhance the sustainability and consolidation of composite structures. The expanded Montornès del Vallès facility is aimed at improving the supply chain by combining state-of-the art automation technology for reliable high-volume rates with best principles of sustainability, resource-efficient production and manufacturing excellence.

Scheduled to go on-stream in June 2019, the Montornès expansion – close to some main European aerospace manufacturing sites – is expected to become fully operational for aerospace products from Henkel by 2021.

“An existing facility had already established our footprint in Spain, so it meant we could add a new greenfield site and use the existing infrastructure – everything that we need in an expanded facility,” Adolph concludes. “For our products aimed at the aerospace sector, everything we’ve built within the plant is brand-new. The initial discussions within Henkel centred on where best to logistically position our site. For example, how far is it away from the existing Airbus and other tier one companies based in Europe?

“The space available at the Montornès facility, plus the transportation infrastructure provides a very good fit. It’s a big step for Henkel and we are doing it in parallel with the build-up of our Development Lab and a second Competence Centre in Dusseldorf – it’s a great package and a clear commitment from Henkel to invest, but if you look at the aircraft build rates coming onstream, it is exactly the right timing for us to make this step.”

In more ways than one, the Montornès facility sees Henkel filling a gap in the aerospace market by continuing to supply its comprehensive portfolio of liquid shim material solutions.

www.henkel.com