FITS AIR Thermoformable panels

Currently, Nomex honeycomb with cured phenolic resin facings are applied for sandwich panels and parts for interiors of aircrafts and trains. Costly hand labor and/or time-consuming curing processes create the Nomex parts.

Generally, fillers, potting compound and metal extrusions add 20-70% weight to the original panel weight. As a result, FITS AIR parts will have a lower weight than Nomex parts.

The current aircraft manufacturing world shows increasing AC building rates. Honeycomb panels, however, lack one or more qualities really required in this aircraft interiors market: high speed, low cost processing: thermoformability, low weight (potting compound), recyclability (due to combining multiple materials), further weight reduction (at the end of Nomex’ technical capabilities).

FITS has invented the FITS AIR thermoplastic sandwich panel and its automated thermoformable application technology. The FITS AIR panel described on this website a PEI (PolyEther Imid of Sabic IP) thermoplastic material was used in the core and the fiber reinforced facings. However different amorphous thermoplastic materils can be used in the fiber reinforced facings e.g. PES, PPSU or PC or combinations thereof. FITS can achieve lower part weight and lower cost goals. It brings all elements required: new design options, enhanced part integration, significant reduced lead time, no hand labor and recyclability.

FITS AIR panels passed all relevant FAA tests. Airbus and Boeing tested FITS AIR panels. They confirm that FITS AIR panels fully comply with aviation fire, smoke and toxicity requirements. (See technical data on this site)

The FITS AIR benefits are the following:

Low cost panel manufacturing technology
Low weight paired with high mechanical and other properties
Automated thermoformable application technology
Potential applications and their weight saving

Low cost panel manufacturing technology

Thanks to the highly automated processes, FITS AIR panels cost is based on the material cost of PEI(PolyEtherImid) and fibers plus a modest manufacturing cost. Total manufacturing cost of FITS AIR panels is significantly below phenolic honeycombs’.

The technology and manufacturing process

FITS AIR panels are manufactured in batch in a press.

For FITS AIR, not only PEI can be used, yet also some other high temperature thermoplastics like PPSU can be applied. For the sake of convenience, we use PEI in this text for all high temperature resistant polymers.

For this process, AIR films impregnated with a physical blowing agent are placed between consolidated fiber reinforced thermoplastic AIR-facings (a pack), before the in-situ foaming takes place:

In a press, a pack is heated under high pressure until a homogenous temperature is obtained to thoroughly connect the AIR in facing to the core.
The pressure is released, and the press is opened allowing the blowing agent in the AIR film to create foam.
The specific opening curvature ensures the creation of vertical cells for high compression strength panels.
At the end of the foaming curve the FITS AIR panel is cooled to room temperature in a cooling curve.
After removing the panel from the press, the Acetone is removed by a patented oven drying process.

Notes:

Acetone is used as a physical blowing agent. The extruded PEI foaming films are soaked in Acetone until saturation. Subsequently, the films are dried to the required level of acetone before processing.
The oven drying process will lower the acetone content to below 0.04% of the panel, to ensure the panels to fully comply with aviation fire, smoke and toxicity requirements.
The facings consist of consolidated fiber reinforced PEI thermoplastic layers.
Carbon, glass or aramid can be used as fibers in the facings in form of UD, fabrics, mats or as a combination thereof.
FITS AIR panels are manufactured in batch in a press (e.g. 4 x 8ft) in 7 minutes per panel.
FITS AIR panels can be manufactured in thickness of 3 to 25 mm, at densities ranging of 80 to 250 kg/m³ with a facing thickness of 0.1 to 0.6 mm.

Low weight paired with high mechanical and other properties

FITS AIR panels are low weight. The total weight of e.g. a standard 10mm panel is approximately 2.5 kg/m². The low weight is the result of:

The strong light weight high compression strength foam.
Very high peel strength.
Strong light weight fibers in the facings.
Absence of adhesive layers between facing and core.

Compared to Honeycomb panels, FITS AIR panels do have comparable mechanical properties in the area of high stiffness/strength and low weight. See also the Technical data for more information.
FITS AIR panels however, besides having the benefit of thermoformable processing, have a series of other benefits over honeycomb panels:

FITS AIR panels are homogeneous, with no length/width direction, so FITS AIR panels with similar in length strength are stronger in width
FITS AIR panels have a very high compression strength
FITS AIR panels have no weak edge effect
FITS AIR panels have a very high peel strength
FITS AIR panels/parts have a higher structural integrity
FITS AIR panels have better mechanical properties at high temperatures
FITS AIR panels have smooth surfaces without telegraphing effect
FITS AIR panels provide better insulation for heat and noise
FITS AIR panels are waterproof and absorbing 80% less water than honeycomb’s
FITS AIR panels are fungus free
FITS AIR panels are fully recyclable

Automated thermoformable application technology

On average, 25% weight is added to the part weight of thermoset Nomex Honeycomb constructions through the application of potting compound, fillers, paint, decorative layers, connections, Aluminum extrusions, etc.

By contrast, with FITS thermoformable panels, only a maximum of 5% weight is added at part level. By applying heat and pressure all kinds of shapes and forms can be created in seconds by automated thermoforming machines. See the section on part manufacturing technology.

Thermoformable application technologies are for example: edge finishing, folding, reinforced corners, welding of inserts, 3D forming and 3D printing. These thermoformable technologies are much simpler, more efficient and more versatile compared to Nomex panels. They allow for automatic manufacturing instead of extensive hand labor as is common for Nomex thermoset panels.

These newly designed parts have 20-60% weight savings, up to 50% cost savings and cycle time improvements from days to minutes. The latter will not only reduce manufacturing cost, it also reduces space requirements and allows for manufacturing in high labor cost countries.

The FITS System brings the required automated part production in the aerospace, rail and ship industries. It is especially suited for large series production.

Potential applications and their weight savings

In the following table lists some aircraft interior application and related weight savings. The weight saving studies were executed with and for some potential customers to demonstrate the large potential of the FITS AIR System.

Product	Estimated Current Weight in gram	Estimated FITS Weight in gram	Twin Aisle Weight saving in kg
OSC without lid ¹	5,500	5,000	40
Table aircraft seat	400	200	60
Swinging cover oxygen masks	230	45	20-25
Fixed cover oxygen system	300	65	26-35
Trolley: 20 per aircraft	16	11	100
¹ Other elements like connections, hinges, deliver a further weight saving of 0.5 kg per OSC

Of course, other parts not listed above will give significant weight savings are. They are not limited to galleys, sidewalls, toilet cabins, doors of toilets, toilet floors and (part of) seats.

Note: We cannot beat Nomex/phenolic constructions at panel weight level. FITS does beat Nomex on part level and on the part manufacturing technology.