In a recent article on DesignNews.com, Boeing announced that it was shifting to plastic composites for its 787 Dreamliner floor beams.  It’s well-known that the airline has had trouble getting this aircraft to market starting with being three years late. But it hasn’t stopped them in finding new, innovative ways to reduce its carbon footprint and drive sustainability into their design decisions:

The Boeing 787 Dreamliner is a long-range airliner that seats 210 to 330 passengers. As a result of a fuselage and wings made primarily of carbon composites, the Dreamliner consumes 20 percent less fuel than the Boeing 767, which has similar seating capacity.

TAL Manufacturing Solutions of India reports that Boeing changed the design for floor beams in the Dreamliner 787 from titanium to a composite plastic structure….the floors will be made from materials that are similar to the materials used in the body of the Dreamliner… The beams will be used for flooring located between passenger and luggage compartments.

In talking with Ken Kozicki from our BISCO Silicones Division, he elaborated on the considerations that are made when choosing materials for aircraft flooring.  He also shared how silicone foam can act as a barrier in between the floor beams and help reduce the vibration and overall noise from engines.  And we all know any reduction in noise when flying is MOST appreciated!  Here’s what Ken said:

Dynamic flooring designs and structures have a few purposes – but can be concentrated into three general categories:

  • Minimize vibration and acoustic noise generation
  • Propagation or “modularize” the floor into segments that can be fabricated and layered prior to final assembly,
  • Shrink the thickness of the profile of the entire floor allowing for increased head room in a rail car or aircraft.

With each of these objectives, the selection of the viscoelastic materials used for the vibration isolation and damping pads is critical.  The performance of the floor is dependent on the material’s physical characteristics such as the stiffness to support maximum loads and the damping coefficient to balance the amount of vibration energy that is isolated versus dissipated.  In addition, especially in the aircraft and rail markets, the materials need to comply to the very stringent flame, smoke, and toxicity standards.

Lastly, something that is often times overlooked is the change in performance of the material over time.  In reference to foams, it is important to consider compression set and stress relaxation.

Compression set is the amount of reduction in thickness the foam will permanently experience over time.  Stress relaxation is how much “springback force” does the material lose over time.  If a solid material is chosen for the pads, other factors such as brittleness and performance capabilities over the required temperature range will be key.

BISCO silicones are a great choice to accommodate all of these conditions.  Noise is generated from two major sources:

1.  The first is the transfer of structure-borne vibration to a propagating sound wave.  Reducing vibration ultimately reduces noise.

2.  The second noise source is propagating sound waves from outside or beneath the flooring structure, such as jet engine noise transferring into the fuselage or rail wheels moving along the tracks.  Sound barrier materials can be laminated to the dynamic flooring structure to block the waves from propagating.  Again, choosing silicone sound barriers is an imperative, especially if a standard such as FAR 25.856 is required.

Can you hear me now?

Images source: http://showpanmohsin.blogspot.com

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