OPTICAL FIBER IN AEROSPACE & DEFENSE APPLICATIONS
Optical fiber Shape sensing has been gaining traction in the Aerospace & Defense industry with several applications. It enables engineers to tackle new design challenges and simplifies aircraft maintenance.
Optical fiber shape sensing for aircraft innovation
The aerospace industry has been increasingly focused on optimizing fuel efficiency, noise reduction, longevity and safety for commercial and military aircraft. To achieve their targets in these areas, engineers are introducing increasingly flexible structures and cutting edge, shape-shifting control surfaces.
Since the shape of these structures drives the control and performance of these next generation aircrafts, fiber optic shape sensing has been identified as a powerful tool to enable and accelerate these innovations.
Shape sensing’s ability to determine position, curvature, and twist in a distributed nature provides an ideal measurement solution for aeroelastic characterization and feedback control. Combined with its small size, environmental robustness, and long fatigue life, optical fiber shape sensing provides measurements which are simply not possible with alternative technologies.
Optical fiber sensors in engine maintenance
Shape sensing is adding value to the tools and processes that keep aircraft flying. Jet engines require a huge amount of continuous maintenance to maximize their life and operate with the utmost safety.
Manual and robotic borescopes are employed to visually inspect and even perform repairs on internal components. Optical fiber shape sensing is being integrated into these devices to enable operators track where they have been, quickly return to previously discovered faults, and store their location as part of the aircrafts’ digital twin.
Many more aerospace & defense applications can benefit from fiber optic shape sensing. Please contact us to discuss your specific requirements.
Background of fiber optic sensing in aerospace applications
NASA began using fiber optic shape and strain sensing systems for flight validation in 2008. The technology allowed it to perform distributed strain sensing and real time structural health monitoring during flight. Compared to traditional sensors, Fiber Optic Sensing (FOS) technology provides an unprecedented level of insight into the behavior of a structure.
A single hair-like optical fiber sensing spanning up to 40 feet can act akin to over thousands of strain gauges without the cumbersome and weight prohibitive instrumentation wire. In addition to strain, FOS can be used to measure temperature, deflection, stress, load, stiffness, and various other critical engineering parameters. By applying fiber with over 3,000 fiber Bragg gratings (FBG) to the wings of the Ikhana unmanned aerial vehicle (UAV), NASA Armstrong was able to monitor stress and observe the deflection of the wings in real-time throughout each mission. This served as the first step to achieving control of the shape of subsonic fixed wing aircrafts.
The capability demonstrated by the sensing system also provided a practical approach to accomplish structural health and loads monitoring. The fiber optic sensing system was environmentally qualified and integrated in the avionics bay of the Ikhana vehicle. In addition to the 3,000 FBG sensors, 16 strain gauges were used to validate the FBG strain measurements. Eight thermocouples were bonded to the upper wings of the vehicle and used for strain gauge thermal compensation.
Subsequently NASA Armstrong used the technology on many different aircrafts, including the X-56 UAV, to investigate challenges associated with highly flexible, lightweight wings. In contrast to stiff, rigid wings found on commercial aircraft today, X-56 is outfitted with long, very high-aspect ratio wings which often flex significantly during flight. The use of more flexible wings is considered essential to next generation, fuel efficient aircraft. Commercial aircrafts currently do not employ wings of this nature due to their susceptibility to the highly destructive aeroelastic instability known as flutter. NASA is utilizing FOS data to identify the onset of flutter and drive active flutter suppression systems.