Today's aircraft structures consist of many different materials. For example, the fuselage and wing structure of the Airbus A350WB is mainly made of composite materials with some metal parts. Here, according to the classic hybrid design, the parts are connected together by bolts and rivets. This design results in increased assembly time, effort, and cost. In addition, in this classic hybrid design, a large number of fasteners introduce unnecessary weight and stress concentration at the point of load introduction.
In the TOAST project, Premium AEROTEC (Augsburg, Germany) is a Tier 1 supplier of A350 fuselage structures, and it proposes a completely new way to connect composite materials and metals. In this way, the disadvantages of the classic hybrid design with bolts and rivets can be eliminated. Premium AEROTEC uses a modern hybrid design to develop and manufacture an aircraft-like brake pad demonstrator in less than five months. It consists of titanium-loaded pull-in fittings made from additive manufacturing (AM) and carbon fiber reinforced polymer (CFRP) thermoplastic composite panels, which are overmolded using thermoplastic composites.
The presenter's innovation is the ability to connect a variety of materials without the need for bolts or fasteners. This can only be achieved through the use of additive manufacturing and thermoplastic overmolding. Titanium fittings are designed with pins on the underside, and the ribs in the spiral structure are easy to produce with AM. AM titanium parts and thermoplastic composite plates are then placed into a thermoforming mold. These two components are pressed together during the thermoforming process followed by an injection molding step. In this step, the V-shaped thermoplastic composite material reinforcing rib is overmolded and pressed into the sponge-like convoluted reinforcing rib of the titanium fitting.
The joint of this hybrid demonstrator is achieved by material connection (CFRP-CFRP) or closed form (titanium AM-CFRP). At the same time, a structural test was performed to determine the mechanical properties of the joint. These tests show that the load transfer capability is similar to that of rivets and bolts.
Compared to classic designs using mechanical fasteners, the advantages of this modern hybrid design include fast manufacturing and assembly without the need for fasteners, fewer parts required, and a shorter and more automated assembly process. In addition, the use of AM and injection molding to increase the efficiency of design freedom can reduce weight. This technique can be applied anywhere that loads must be transferred between points and surfaces.
Premium AEROTEC is the world's first component manufacturer to provide continuous production of 3D printed components made of titanium alloys for aircraft. Premium AEROTEC is a global player in the aviation industry, with a turnover of 2 billion euros in 2018. Its core business is the design and manufacture of metal and carbon fiber composite aircraft structures. The company has factories in Augsburg, Bremen, Hamburg, Nordenham and Varel, Germany, and Brasov, Romania. Premium AEROTEC has approximately 10,000 employees worldwide.