Electromagnetic interference (EMI) immune and light-weight, fiber-optic sensor based Structural Health Monitoring
(SHM) will find increasing application in aerospace structures ranging from aircraft wings to jet engine vanes. Intelligent
Fiber Optic Systems Corporation (IFOS) has been developing multi-functional fiber Bragg grating (FBG) sensor systems
including parallel processing FBG interrogators combined with advanced signal processing for SHM, structural state
sensing and load monitoring applications. This paper reports work with Auburn University on embedding and testing
FBG sensor arrays in a quarter scale model of a T38 composite wing. The wing was designed and manufactured using
fabric reinforced polymer matrix composites. FBG sensors were embedded under the top layer of the composite. Their
positions were chosen based on strain maps determined by finite element analysis. Static and dynamic testing confirmed
expected response from the FBGs. The demonstrated technology has the potential to be further developed into an
autonomous onboard system to perform load monitoring, SHM and Non-Destructive Evaluation (NDE) of composite
aerospace structures (wings and rotorcraft blades). This platform technology could also be applied to flight testing of
morphing and aero-elastic control surfaces.
MEMS gyroscopes are used in many applications including harsh environments such as high-power, high-frequency
acoustic noise. If the latter is at the natural frequency of the gyroscope, the proof mass will be overexcited giving rise to
a corrupted gyroscope output. To mitigate the effect of the
high-power, high-frequency acoustic noise, it is proposed to
use nickel microfibrous sheets as an acoustic damper. For this purpose, the characterization of vibration damping in
Nickel microfibrous sheets was examined in the present research effort. The sheets were made from nickel fibers with
cellulose as a binding agent using a wet-lay papermaking technique. Sintering was done at 1000 °C to remove all the
cellulose giving rise to a porous material. Square sheets of 20 cm were made from three diameters of nickel fibers
namely 4, 8, and 12 microns. The sheets were cut into smaller pieces to fit the requirements of a fixture specially
designed for this study. The fixture was attached to a LDS V408 shaker with a mass resting on a stack of the
microfibrous sheets to simulate transmitted vibration by base motion with the sheet stack acting as a damper. A series of
experiments was conducted using these 3 fiber diameters, different number of layers of microfibrous sheets and varying
the vibration amplitude. From the collected vibration data, the stiffness and damping ratio of the microfibrous material
was characterized.
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