Bionic design and additive technology in modern aircraft engineering

A design methodology in which computer technology allows the process of automatic generation of created objects to be managed is called generative design. The most efficient result is achieved by allowing the designer to make an informed decision when selecting the final version of the product to be designed. Using the built-in CAD programming languages, the designer can create his own decision generation algorithms, using the potential of neural networks. On previously trained models, the system independently extracts dependencies from the dataset, this is called ‘machine learning’ or ‘artificial intelligence’.

In this approach, it is possible to use a search algorithm based on the mechanisms of biological evolution, where the creation of variations and their evaluation is performed by the system itself, minimising human involvement in intermediate search iterations. Objects designed in this way are externally distinct from conventional man-made products and have distinct features, such as those found in plants, or mimic the structure of limbs or bones. That is why this way of design is often called bionic design, and the term «generative design» is used in connection with the fact that the geometry of such structures is generated by a computer-aided design system.

The main objective of bionic design is to reduce an object’s weight while maintaining or even increasing its original strength. That’s why such solutions are in demand in the aerospace industry, where every saved kilo leads to improved performance, controllability and aerodynamics, as well as higher cost-effectiveness of the end product.

Another related challenge in generative design is saving expensive materials such as complex alloys or rare metals. The bionic approach to design allows some processes to spend 30 or even 50 per cent less material. As a consequence, this has a positive effect on the cost of such products.

Additive technologies work closely with bionic design. Traditional production methods are not able to realise projects with the complex structure of non-standard elements that bionic design offers. Today, in most cases, the creation of new, complex structures is only possible through 3D printing, where a physical object is «printed» from a digital 3D model using layer-by-layer deposition. Additive technologies make it possible to produce elements of any thickness, curvature, cavity, mesh and cellular structure. In addition, layer-by-layer construction gives bionic objects even greater strength and resistance to stresses.

The first part based on the bionic design was developed by Sukhoi Design Bureau, an aluminium power bracket for the Su-57 fighter (pictured). «Sukhoi became one of the pioneers in the application of electronic mockup of the product using high-performance computing. The Sukhoi Design Bureau’s centre for supercomputer technology investigated models of aircraft movement at high angles of attack, unsteady aerodynamics for deflected controls and their failures, and solved numerous problems in the use of aerial weapons and detachable cargoes. The bionic arm was also developed using the Centre’s facilities.

Specialists at the All-Russian Scientific Research Institute of Aviation Materials (VIAM) have printed a part on a 3D printer from a domestic metal powder composition of an aluminium alloy. The design looks more like the bone of some prehistoric animal than a part of a fifth-generation fighter jet. The new bracket is a quarter of the weight of its conventional predecessor. The almost half-metre long piece was produced by laser sintering in just one night. Machining a billet of aluminium using conventional methods would have taken at least a week. Thanks to the use of 3D printing, it was possible to create cavities in the part that would be impossible to reach with a conventional computer-controlled machine when machining the part.

The Sukhoi Design Bureau has its own 3D laboratory, where dozens of different aircraft parts are made using the stereolithography method. Parts made using this method are very familiar to pilots of the Su-57 fighters. For instance, there are several functional buttons on the control knob, which were not always within reach of the pilot’s fingers. Following comments made by the pilots, the Design Bureau engineers quickly refined the initial design and proposed a more comfortable version, which was printed on the Design Bureau’s 3D printer.

The aeroplane’s control pedal was also printed by layer-by-layer fusion and then cast into metal. In addition, many details using additive technologies are made for the blowing models of new aircraft. The use of 3D printing methods makes it possible to quickly modify the design of a single piece of equipment, such as a bracket, and put it into production.

From a purely external perspective, 3D-printed parts look unlike most structural components that have been designed in recent decades. Over time, thanks to their lighter weight and ease of production, they could replace conventional parts.