Smart material

The so-called smart materials technology was born from an attempt to replicate nature by trying to obtain elements that in some way react to their environment in a predictable way. It is easy to understand that if we have materials capable of adapting to aerodynamic flows, as the wings of a bird do, for example, we will be able to take a big leap in obtaining much more efficient and versatile designs.

The aviation industry is undergoing a technological revolution driven by the need for more efficient, lighter, and more adaptable aircraft. One of the emerging technologies leading this change is the development and application of smart materials. These materials are capable of responding dynamically to external stimuli such as temperature, pressure, electric or magnetic fields, and mechanical stress, offering adaptability and enhancing the performance of critical aircraft components.

Smart materials are particularly attractive for the design of flight surfaces, such as wings and control surfaces, as they enable real-time adaptation to changing environmental and operational conditions. This adaptability can result in improved aerodynamics, reduced fuel consumption, and enhanced safety. To fully understand the potential of smart materials in aircraft design, it’s essential to explore the concept, typology, associated technologies, and their specific applications in aviation.

Concept of smart materials

Smart materials refer to materials that can change their properties in response to external stimuli in a controlled and reversible way. This responsiveness to environmental conditions makes them “smart,” as they can adjust their behavior without the need for manual intervention.

Key characteristics of smart materials:

• Self-regulation: The ability to react autonomously to changes in the environment.
• Reversibility: The changes induced in the material can often be reversed when the stimulus is removed.
• Adaptability: The material can tailor its properties to improve performance, such as altering its stiffness or shape.

In aerospace, these properties are highly valued as they can lead to improvements in fuel efficiency, performance, safety, and maintenance costs.

Types of smart materials

Smart materials encompass a wide range of technologies, each with distinct capabilities and applications. The most relevant types of smart materials in aircraft design include:

1. Piezoelectric materials

Piezoelectric materials generate an electrical charge when mechanically stressed and conversely change shape when an electric field is applied. This dual capability makes them useful for sensors, actuators, and energy harvesting applications.

Applications in aerospace:

• Control wing surfaces.
• Vibration damping to reduce fatigue and extend component lifespan.

2. Shape memory alloys (SMAs)

SMAs can “remember” their original shape and return to it after being deformed when exposed to heat or another stimulus. They exhibit pseudo elasticity and super elasticity.

Applications:

• Adaptive wing designs.
• Simplification of mechanical systems in aircraft.

3. Magnetostrictive materials

These materials change shape or dimensions in response to magnetic fields and are used in environments where magnetic fields are more practical than electric fields.

4. Electrorheological (ER) and magnetorheological (MR) fluids

These fluids can change their viscosity rapidly when exposed to an electric or magnetic field, making them suitable for suspension and damping applications.

5. Electroactive polymers (EAPs)

EAPs mimic the behavior of biological muscles, undergoing significant deformation in response to electrical stimulation.

6. Shape memory polymers (SMPs)

Lightweight and easier to process than SMAs, SMPs are used in structures that need to adapt to temperature variations or flight load conditions.

7. Thermochromic and electrochromic materials

These materials change color or opacity in response to temperature or electrical stimuli, offering functional and aesthetic enhancements in aircraft.

8. Carbon nanotubes (CNTs) and graphene

While not traditional “smart materials,” CNTs and graphene are increasingly used in composites to improve strength, conductivity, and resistance to environmental factors.

Associated technologies for smart materials

To effectively implement these materials in industry, supporting technologies are essential:

• Additive manufacturing (3D printing): Enables precise layering and combination of materials.
• Structural health monitoring (SHM): Detects micro-damage or stress in real time.
• Actuation systems: Uses SMAs and EAPs for efficient control of flight surfaces.
• Sensor integration: Allows the development of smart wings that adjust flight dynamics in real time.

Applications of smart materials in aircraft design

Morphing wings

Smart materials enable wings to change shape mid-flight, optimizing aerodynamics and reducing fuel consumption.

Adaptive control surfaces

Surfaces that adjust their aerodynamic profile improve lift, reduce drag, and enhance stability during flight.

Vibration and noise damping

Piezoelectric materials and EAPs are employed to enhance passenger comfort and structural longevity.

Energy harvesting

Piezoelectric materials convert vibrations into electrical energy for powering sensors and small electronic systems.

Ice protection systems

Smart materials prevent ice accumulation on wings and control surfaces, ensuring safety during cold-weather operations.