Composite aerospace structures that use a combination of shape memory alloys (SMA) and optical fibres to respond to and monitor in-flight stresses are being developed by Swiss researchers.

To resist vibration and structural loading, composites need to be as stiff as possible when needed and have adaptive damping properties, while remaining lightweight.

The problem with today's composites is they have conflicting stiffness and vibration damping characteristics. Researchers believe that the use of SMA could resolve this problem.

These fibres change their stiffness, but not their shape, with the application of heat or electricity. This changes the tension in this new composite system, which could provide both damping and stiffness capabilities.

Such an SMA composite structure could be 60% carbonfibre, 36% matrix material and epoxy resin, with the remaining 3-4% consisting of fibres of a shape memory alloy such as nickel titanium.

The SMA material is then combined with optical fibres because they can act as strain sensors, through the observation of light reflections along the length of the optical fibres (Flight International, 20-26 July).

The interface between these optical fibres and the epoxy and the nickel titanium fibres is the focus of current research.

The combination of SMAs and optical fibres has led the industry to classify it under smart composite technology.



Source: Flight International