FACC Operations Relies on DELO Adhesive for Overhead Stowage Bins Made of Composite Material | Any development in the aviation industry focuses on making airplanes safer, more comfortable, and more efficient, while also reducing their weights and environmental impacts. 20 years ago, only two percent of an aircraft's structure was made of composite materials, whereas nowadays these materials account for more than 50 percent. Metal parts are more and more replaced by novel composite materials, and that is where adhesive bonding is the preferred joining method.
As a pioneer of composite technologies, the Austrian company, FACC Operations GmbH, has been a leader in design, development, and production of components and systems made of composite materials for the aviation industry. Reportedly, no other company of this field of industry has its lightweight composite components installed in so many aircraft models. Its range of products includes structural components for the fuselage and wings such as aerodynamic winglets, panels and covers in the engine area as well as complete passenger cabins for commercial aircraft, business jets, and helicopters.
In the business year of 2015/16, the tier-1 supplier achieved a turnover of 587.5 million Euros. The company currently employs more than 3,300 employees worldwide. FACC produces for all large aircraft manufacturers such as Boeing, Airbus, Bombardier, Embraer, Sukhoi, and COMAC, as well as for all important engine manufacturers and sub-suppliers.
Convenient & Functional
As far as the interior of passenger aircraft is concerned, OEMs demand light weight and longevity of overhead stowage bins, entertainment systems, lavatories, etc. Passengers seek comfort and an attractive design. In the case of the FACC Operations luggage compartments, used, for example, in the Airbus A380 and the A320 family, the Interior Division relies on composite materials in the form of honeycomb panels. Aramid fibers coated with phenolic resin make the material light and robust. Well known trademark names of aramid fibers are Nomex or Kevlar, for example. A transparent, decorative film of polyvinyl fluoride is then applied to the surfaces. Apart from being dirt-repellent and chemical-resistant, this decorative film gives a pleasant feel to the surfaces and provides an attractive appearance.
The composite sandwich panels feature low weight and high torsion resistance, while being completely flat as semi-finished products. Further machining will be required for bent or angled structures. This process takes place at the FACC Operations Interiors plant, located in the Austrian town Ort im Innkreis. Using the so-called "ditch & pot" technology, the honeycomb structure is cut from the back of the composite sandwich panel. This allows the panel to be easily bent or angled at that point. The resulting cavity is then filled with adhesive. Once cured, the adhesive will permanently keep the sandwich panel in the desired shape.
Long Processing Time for Manual Operations
FACC Operations made some demands on the adhesive: Considering the expected amount of adhesive, they preferred a two-component type with a mixing ratio of 1:1 to simplify production. In addition, high strength is required, since the panels are used in luggage storage compartments. Products based on epoxy resin meet this requirement very well. Due to the manual production process and any necessary finishing work on the component, the processing time of a 100 g batch should be at least 30 minutes, while curing time until initial strength at room temperature should not exceed five hours.
The double chamber cartridge dispensing system allows the thixotropic epoxy resin to be quickly and easily applied, just like a one-component adhesive. The adhesive fully cures at room temperature within the given parameters. Curing can be significantly accelerated by increasing the temperature to +60 °C, for example, thus allowing production cycle times to be reduced without affecting the final strength.
Flame Protection Confirmed by Fire-Smoke-Toxicity Test
After intensive testing, FACC Operations opted for the new DELO-DUOPOX AB8390, specifically developed by DELO for aircraft interiors, and especially designed for ditch & pot applications on sandwich panels. Further tests proved the versatility of this construction adhesive, since it would also be suitable for bonding of load-bearing joints with inserts.
DELO-DUOPOX AB8390 not only fulfills all the requirements already mentioned, but also as a "standalone" product, it complies with the specifications prescribed by the national aviation authorities. This includes, for example, fire protection in aircraft interiors, to be guaranteed by the Flame-Smoke-Toxicity (FST) test. In addition, the adhesive complies with RoHS Directive 2015/863/EU.
Permanently White Construction Adhesive
The flame-retardant adhesive features good strength and high chemical resistance at temperatures ranging from -55 °C to +85 °C, as relevant for aircraft interiors. For example, the tensile shear strength of two sand-blasted, bonded standard specimens made of aluminum is 25 MPa. This value is almost reached even after 500 hours of storage at +70 °C in a reference fluid for Skydrol (tri-n-butylphosphate).
DELO-DUOPOX AB8390 is extremely colorfast, keeping its white color even after 1,000 hours of storage at +70 °C and an air humidity of 85 %. FACC Operations can thus rely on consistent colors to maintain the appearance of their aircraft components such as those used for luggage storage compartments.
