Strain Sensing for Highly Elastic Materials

Strain Sensing for Highly Elastic Materials

A research team at Armstrong is developing a sensor that can measure strain on highly elastic materials, such as inflatable wings, reentry vehicles, and airships. Conventional foil strain gauges are inaccurate when used on highly elastic materials because of localized stiffening due to the relatively high modulus of sensors and their adhesive mechanisms, which reduces strain transfer to the sensing element. To counteract these problems, the Armstrong team has adapted a strain measuring device currently used in the medical field to diagnose endothelial dysfunction.

Work to date: Laboratory testing and sensor calibration has been achieved during testing of eight 11- to 17-foot diameter tori from the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) vehicle. Under compressive loading, strain levels at buckling were determined with the data generated from these sensors.

Looking ahead: The team will continue to characterize and evaluate the sensor and flexible adhesive.

Benefits

 Broader range of measurement:

Measures high strains (over 100 percent)

 More accurate: Works without creating localized stiffening that could bias strain measurements

Applications

 Gulfstream III test aircraft  Inflatable wings

 Reentry vehicles  Airships

 Fiber Optic Sensing

Armstrong's portfolio of Fiber Optic Sensing System (FOSS) technologies offers unparalleled options for high-resolution sensing in applications that require a unique combination of high-powered processing and lightweight, flexible, and robust sensors. The system measures real-time strain, which can be used to determine two-dimensional and three-dimensional shape, temperature, liquid level, pressure, and loads, alone or in combination. Initially developed to monitor aircraft structures in flight, the system's capabilities open up myriad new applications for fiber optics-not just in aerospace but also for civil structures, transportation, oil and gas, medical, and many more industries.

The Armstrong approach employs fiber Bragg grating (FBG) sensors, optical frequency domain reflectometry (OFDR) sensing, and ultra-efficient algo-rithms (100 samples/second). Engineers are continually seeking new ways of looking at information and determining what is important. Armstrong's FOSS technologies focus on critical research needs. Whether it is used to determine shape, stress, temperature, pressure, strength, operational load, or liquid level, this technology offers ultra-fast, reliable measurements.