6 Polymer Technology Trends in Aerospace
By
Assist. Lec. Rand Fadhil Kadhim
Plastic materials are seeing increased use in aircraft and spacecraft to reduce weight,
improve quality, and lower manufacturing and maintenance costs.
1. Using antimicrobial plastics that have enhanced compatibility
with disinfectants for aircraft interiors.
Due to the COVID-19 pandemic, aircraft interior surfaces are being cleaned and
disinfected in ways that can quickly degrade traditional plastic materials. New
antimicrobial and disinfectant-resistant plastics initially developed for use in
hospitals are now being specified for aircraft interiors. These materials are
formulated to meet the stringent flame, smoke, toxicity, and heat-release standards
required for commercial aircraft.
2. Specifying high-strength thermoplastic composites for weight
savings, improved fuel efficiency.
Aerospace structures requiring high strength and stiffness have traditionally been
made from metals or thermoset composites. However, these materials have some
significant limitations. Metals are heavy, limiting their use for aerospace
applications where light weight is desired. Thermoset composites tend to be brittle,
often having poor chemical resistance. Thermoset manufacturing is laborintensive, with most thermoset composite materials not suitable for temperatures
above 100°C.
A new class of thermoplastic composites developed by Ensinger has strength and
modulus (stiffness) values comparable to metals and thermosets. The technology
involves continuous glass fibers or carbon fibers embedded in a thermoplastic
polymer matrix, usually consisting of polyetheretherketone (PEEK) or Ultem PEI
(polyetherimide). Since the matrix is made from high-performance, thermally
stable plastics, these composites can be used at elevated temperatures.
Thermoplastic composites offer many advantages associated with thermoplastics
including ductility, fatigue resistance, and vibration damping characteristics, as
well as resistance to fuels, lubricants, and cleaning chemicals. Sheet stock made
from these materials can be quickly formed into finished parts using heated metal
tooling, lowering manufacturing costs.
3. Choosing plastics that don’t interfere with radio frequency (RF)
signals for high-performance communications radomes.
The proliferation of unmanned aerial vehicles (UAVs), drones, and satellites that
rely on RF signals to control flight operations has increased demand for highly
reliable antennas. Optimum antenna function requires plastic radomes that won’t
significantly attenuate RF signals at the desired frequency and throughout the
device’s operating temperature range. Specialized engineering plastics with low
dielectric constants and low dissipation factors as well as enhanced toughness,
ultra-violet (UV) resistance, and thermoformability are becoming more widely
specified for use as protective antenna radomes.
4. Selecting durable, high temperature plastics to separate metal
surfaces for improved reliability.
Metal-to-metal connections are often points of failure in aircraft assemblies due to
inherent problems when mated metal surfaces are subjected to vibration and/or
sliding wear. Increasingly, designers are specifying ductile, high-performance
polyimide materials for applications such as spline couplings and the anti-rotation
elements of locking fasteners to separate metal parts. Introducing the polymer
element into the assembly increases service life and extends time between
required maintenance cycles.
For spline connections that transmit power to various aircraft systems through
connected rotating metal shafts, high-temperature couplings made from DuPont
Vespel polyimide are installed between mating metal splines for smoother
operation and longer life. The approach reduces spline wear when the rotating
metal shafts are slightly misaligned. Ductility of the polymer allows for shaft
misalignment without creating excessive stress on the metal shafts, bearings, or
drive motors.
In aerospace locking fasteners, DuPont Vespel polyimide is used as a ductile
locking element in a nut or a bolt to prevent unwanted rotation without damaging
the mating metal fastener during assembly or disassembly for maintenance. This
polymer element prevents the galling associated with all metal locking fastener
designs.
For both examples, ductility and wear performance of the polymer mitigates problems
associated with metal- on-metal contact.
5. Opting for low flammability, high dielectric strength plastics for
electrical insulation.
Plastics have long been the prefered material for applications requiring electrical
insulating properties. Electrical systems for modern military and civilian aircraft can
be particularly challenging since – in addition to having good dielectric strength
and resistance to electrical arcing – polymer insulators must be resistant to aircraft
fuels and lubricants; withstand vibration, wear, and fatigue; and have outstanding
flammability properties. Plastic insulators in aircraft may also have to operate
throughout a broad temperature range – from extremely cold at cruising altitudes
to extremely hot near jet engines.
Aircraft electrical system designers are now specifying fluoropolymers such as
polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), and
perfluoroalkoxy alkanes (PFA) as well as high performance thermoplastics
including PEEK, Ultem PEI, and DuPont Vespel for demanding aerospace
electrical applications including standoff insulators, shrink tubing, and flexible wire
wrap insulation.
6. Employing innovative polymers to create upscale aircraft
interiors.
Commercial aircraft are becoming increasingly more upscale, with interiors rivaling
luxury hotel lobbies. Printed graphics have traditionally been problematic for
aircraft interiors since high-traffic areas are exposed to wear and repeated cleaning
that can quickly degrade printing.
Newer technologies such as Infused Imaging with KYDEX thermoplastics allow
designers to create customized environments using imagery that’s in the material
not on it.
There have also been significant advances in the plastic lens material used to
manage and transmit light on commercial aircraft. New polymer formulations allow
for high light transmission, excellent diffusion, and precise color control of LED
lamps. Light management using high-performance plastics is positively impacting
the aesthetics of aircraft interior spaces.