The Role of Nanotechnology

The development of nanotechnology provides an opportunity to improve multifunctional properties (physical, chemical, mechanical properties, etc.) at the nanoscale. Unlike conventional composites, nanocomposites offer the opportunity to improve properties without too much tradeoff of density increase by only adding a small amount of nanoparticles (e.g. layered silicate, functionalized carbon nanotubes (CNTs), and graphite flakes). To increase the oxidation resistance of composites, for example, nanoparticles could be included such as silicate, CNTs, or polyhedral oligomeric silsesquioxane (POSS) that could form passivation layers.

The addition of CNTs, silica, and layered silicate into composite matrix could promote energy dissipation on structural failure, increasing the toughness of the composite and resulting in the potential application to high-damage-tolerance structures. In addition to high modulus, high-strength nanoparticles such as continuous CNT could improve the stiffness and strength of the composite.

The development of nanocomposites offers the opportunity for redundancy elimination and weight reduction, which provides significant potential in promoting the properties of aerospace components, especially in lightweighting.

Advanced Manufacturing

Manufacturability is a crucial constraint throughout the design process, governing the possibility of whether a design can be fabricated into a real product. Manufacturing constraints must be taken into consideration during materials selection, structure design, and optimization. Topological optimized designs tend to result in a complex geometry that cannot be fabricated by conventional manufacturing methods, such as casting and forming, without modification. Hence, manufacturing methods have significant effect on lightweighting design.

The development of advanced manufacturing technology, such as additive manufacturing (AM), foam metal manufacturing, and advanced metal forming, could significantly expand the flexibility of lightweighting design, both in material selection and in structural optimization.

AM was initially developed to produce prototypes rapidly and has now become a standard manufacturing tool. Although the advantages of AM attract much attention, challenges exist for AM to compete with conventional manufacturing methods, including quality of fabricated components, time-consuming processes, relatively expensive raw materials, and establishment of standards, qualification requirements, and certification.

Conclusions

Selection of materials for an aerospace system is based on the operating conditions of the specific component or system — such as loading conditions, operating temperatures, moisture, corrosion conditions, and noise — in combination with economic and regulatory factors; for example, wings mainly sustain bending during service as well as tension, torsion, vibration, and fatigue. Hence, the main constraints for wing materials are stiffness, tensile strength, compressive strength, buckling strength, and vibration. Composites such as CFRPs and GLAREs usually have much higher specific strength and stiffness than metals, which makes composites an attractive choice for lightweighting design for many aerospace components and systems; however, metals have the advantages of ease of manufacture and availability as well as much lower cost, making them still extensively used in many aerospace applications.

Lightweighting represents an effective way to achieve energy consumption reduction and performance enhancement. This concept has been well accepted and utilized in many industries, especially in aerospace component and system design. Lightweighting design involves the use of advanced lightweight material and numerical structural optimization, enabled by advanced manufacturing methods.

This article was written by L. Zhu, N. Li, and P.R.N. Childs of the Imperial College London, UK. Learn more here.