Circular aviation begins with design, the first phase in an aircraft life cycle. Circular design for aircraft is still an emerging concept in aviation and aerospace, but holds much promise. In the second edition of our Sustainability Snapshots series, we explore what circular design for aircraft entails, and how SUSTAINair seeks to deliver on this crucial solution for circular aviation.
Rethinking aircraft design for the circular economy
Aircraft manufacturers and aerospace engineers have fueled substantial innovation in aircraft design. In the past decades, they have succeeded in making aircraft e.g. more lightweight and aerodynamic. As a result, modern aircraft have made substantial progress in fuel efficiency and emission reduction. Nowadays, aircraft leaders like Airbus are even looking to imitate nature to rethink innovative aircraft design.
But rethinking innovative aircraft design needs to do more than e.g. imitating nature: it should also aim at working in harmony with nature. This is where circular design comes in. In circular design, the focus lies on creating products for the circular economy. The key is to design products and their components in a way that they can be useful repeatedly, by being repairable, reusable, recyclable or transformable. This minimizes waste, reduces resource consumption and ensures that products and their parts can get a ‘second life’.
Circular design applied to aircraft therefore requires a paradigm shift to how aircraft are currently designed. Aircraft design presently focuses to a large extent on the initial value of the aircraft and its parts for their ‘first life’. It neglects however the full picture of an aircraft lifecycle, and the vast potential that lies in the second life for aircraft and its parts. Circular design can overcome this limitation, and thereby take innovative aircraft design to the next level.
Circular design for aircraft in practice
Designing aircraft with circularity in mind means rethinking all design aspects from the bottom-up. It firstly entails taking design decisions based on the cost of the entire aircraft lifecycle. This means cradle-to-cradle, including resourcing raw materials and disposal at end of life. The aim is to design aircraft in a way that they can be easily dismantled, and then its parts reused, repaired or recycled. This supports increased availability for reuse and repair, as well as increased quality of recycled material. It also decreases the costs associated with each option. Moreover, it supports the reduction of waste from material that cannot be recycled.
In practice, circular design for aircraft focuses on five areas – standardized design, durability, modularity, choice of materials and design for disassembly. With standardized design, the objective is to create parts/assemblies that can be removed from one aircraft and placed unchanged into another. Durability means designing parts with strong structural integrity and ease to repair/upgrade. Modularity (e.g. reconfigurable interiors) increases the life span of the underlying aircraft platform. Choice of materials entails the use of (dissimilar) materials that can be readily recycled, such as thermoplastic composites. Non-recyclable materials are eliminated as much as possible from the material mix employed. Finally, design for disassembly makes use of reversible joints and interfaces of dissimilar materials. This maximizes the recovery of valuable materials and parts.
SUSTAINair project's contribution
SUSTAINair will focus in its research on the circular design of individual components and joining technologies for airframe construction. The project’s aim is to enable lightweight design with largely recyclable materials and embedded functionalities. This includes:
- Design requirements for aircraft applications with particular focus on first and second life materials and integration of Structural Health Monitoring (SHM).
- Circular design for coupons, i.e. small samples of the material(s) used for material characterization.
- Circular design for structural elements, i.e. hybrid joints used for various analysis.
- Design for flexible wing with morphing capabilities, increasing aircraft performance while enabling circular alternatives to maintenance, repair, and overhaul operations (MRO).
In its approach to circular design for aircraft, SUSTAINair’s design philosophy will focus especially on four areas. Firstly, it will consider repair and recycling in its approach. Secondly, it will concentrate on manufacturing and joining technologies for metal, composites and multi-material designs. Thirdly, the project will explore integrated systems of sensors for SHM and damage diagnosis. Finally, it will focus on flexible structures with morphing capabilities. Ultimately, SUSTAINair’s approach will give priority to low weight and safety, but also bring multiple environmental benefits during operation and in material efficiency. This will include reduced maintenance efforts, fuel consumption, extended durability, recyclability of materials and valorizing recycled feedstock to design parts.