A tasty new sandwich filling!

A one-polymer system is threatening to shake up the aerospace interiors industry – traditionally a sphere dominated by phenolic resin honeycomb panels. Pennie Varvarides reports. A thermoplastic sandwich panel from French firm SMTC has been reported to offer significant weight and cost savings in aircraft interior applications.

“Dynatech is a new material we are developing, which basically will be a competitor to the usual solutions, such as honeycomb with phenolic resin used for all the partition work,” begins SMTC's northern Europe business developer, Jean Emmanuel Wattier. “This will be lighter, cheaper and easier to recycle. It's better for everything.”

Dynatech's thermoplastic nature as a ready-to-be-formed sandwich system for mass production means it can be used for the manufacturing of various complex-shaped parts for the interior of aircraft and trains – such as galleys, tables, overhead-bins, seats, doors and luggage compartments.

The material is thinner and lighter than traditional honeycomb systems, which opens doors to new design opportunities and greater space and comfort within an aircraft. Unlike the honeycomb structure, the Dynatech foam is cylindrical. “It's like loads of little cubes,” Wattier explains. “That's what gives it strength.”

The product was developed from the Foamed In-situ Thermoplastic Sandwich (FITS) technology patented by Dutch company FITS Technology. The panels are based on polythylenimine (PEI) and comprise a PEI in-situ foamed core sandwiched between fibre reinforced PEI facings. “It's made of one matter only,” notes Wattier. “This means it is completely recyclable. It can be melted back down.

“The process is different to honeycomb and the resin is different. That's what gives the benefit to Dynatech. The core material is just a film and when you warm it up it becomes a foam.”

SMTC's managing director, Christophe Jenny adds: “With Dynatech, we proactively made a major investment in mass production with high repeatability in order to better serve our customers' needs regarding significant weight savings, better mechanical properties, lower total system costs and recyclability.”

Finding the right fit

SMTC has been designing and manufacturing sandwich panels for the transport industry for 30 years. Formally, it was focused on producing aluminium-based honeycomb systems for OEM customers and tier 1 suppliers in the aerospace and train industries, including Zodiac Aerospace and Siemens.

The French firm spent a year carrying out market research looking for a technology that would meet the future sustainability requirements of its customers. The sandwich panels from FITS Technology seemed to be exactly what the SMTC team was looking for. After a performance test and numerous discussions with OEMs, SMTC decided to acquire Dynatech from its Dutch inventor.

Dynatech was only announced earlier this year and is currently still in development. As it stands, SMTC is able to produce 1m2 prototype panels.

Wattier says: “The next step will be to qualify the properties. We have been running some tests and we have it qualified, but we still need to run the testing again. We're working on producing the panels by 2016.”

In 2015, SMTC will invest in a large production facility in France for manufacturing the panels and shaping them into parts. The firm expects to have a high-volume production line up and running by the following year. The whole process is automated, and therefore much less labour-intensive than traditional production processes. The cycle times for pressing Dynatech panels takes just a few minutes, with a manufacturing time of no more than 30 seconds per edge. Edges are closed using a press equipped with heated tooling. Heat enables deformation of the panel and pressing allows it to take the desired shape.

“The whole process is made easier with Dynatech,” reckons Wattier. The material is semi-foldable, which means one panel can be used to make corners by warming a section up and bending it into place. “It's a benefit because if you need to make a corner with the old system, you'd have to produce two different panels and then make a joint profile in the middle to put them together. With our system you just need one panel, which you can bend to make a corner; so you save weight and it requires less labour, so you save money.”

Panels can be manufactured with a thickness of between 3.2-25mm, with an in-situ foam density of 80-250kg/m3 and facing thickness of 0.1-0.6mm. Because it's a thermoplastic system, Dynatech is easy to thermoform and shape, and parts can be manufactured in a few minutes.

What's particularly interesting is the ageing of this single polymer system. Because Dynatech does not absorb humidity, unlike its honeycomb counterpart, it should be able to hold its shape and strength throughout its lifetime. “It's also not going to grow fungus,” adds Wattier.

A study has been completed looking at Dynatech aboard an Airbus A350. The aim was to estimate the savings achievable if Dynatech panels are used for all interior parts. Wattier says that by using it in all possible places, 750kg can be saved per aircraft when compared to honeycomb interiors.

The weight is over

A large aircraft will contain around six tonnes of interior parts. SMTC estimates a potential to cut weight by 20%-40%, while saving 10%-30% on cost. An estimated 400kg can be saved from side walls, seats and luggage bins; 25kg from galley doors; 300kg from trollies; 75kg from seat tables; and 55kg from the oxygen cover and box.

“When I speak about weight savings and cost reductions, I'm talking about the complete final cost system – not the basic panel. What I mean is that we save weight and cost when you compare the whole thing. So, one galley made of Dynatech will be cheaper and lighter than one made in honeycomb.”

Over a period of 20 years, a saving of one tonne will lead to fuel savings of €3 million and a reduction in carbon dioxide emissions of 120 tonnes. That's about a 20% reduction.

The thinner, more malleable panels allow for more space within the aircraft interior, as well as create greater flexibility in design opportunities.

The technology hasn't been officially approved yet, “but it meets all the requirements to be so”. It will be interesting to see what happens in a couple of years' time, when Dynatech is ready to be specified in aircraft interiors. Will designers take the opportunity to shake things up a bit?

www.smtc.fr