Since the mid 1970’s, the use of fiber reinforced composites is a well-known and often used technology in the construction of cladding and structural parts in civil aircrafts. Focusing on multiple positive lightweight effects, a pressure cap made of CFR was introduced to the public by Premium Aerotec at the 2018 ILA in Berlin.
The pressure cap is designed to fit the pressurized passenger cabin of an Airbus A 320 and does not only impress with its weight savings compared to its aluminum predecessor but can also mainly impress with its joining process and the associated automation potential.
One of the main technological advances is the manufacturing process using electrical resistance welding. This process is ideally matched to the material combination of carbon fiber and thermoplastic matrix. The pressure cap, which is made of eight separate segments, can thus be joined in a materially bonded manner by melting the thermoplastic composite, which leads to an ideal joining zone. In contrast to riveting and the associated pre-drilling of joining zones, this process is clean and faster, which is reflected in low costs and short production cycle times.
The use of a fiber matrix composite especially makes sense if it comes to high pressure forces which can be absorbed by radially arranged fibers, stressed in fiber direction. The objective for production is to store the fibers in a load-oriented manner, but without the use of an autoclave or vacuum chamber, which results in a reduction of cycle times and a straightforward production process.
Cut-outs in the dome are partially reinforced by radial fiber layers to design the component to be load-appropriate and weight-optimized. In the Airbus A380 the CFR construction even works for a 6-meter pressure cap, whereby this concept has to be additionally stiffened by further ribs with a foam core in order to guarantee the passengers a comfortable pressure level corresponding to about 2000 meters of altitude.
The Lightweighting Effect
The weight saving potential of this process is around 25 % compared to a standard aluminum pressure cap, whereby the manufacturing advantages and short cycle times are equally responsible to the success of this concept.