Case Number 103046 - Artificial Neural System
Contact: Geoffrey Pinski
Description: This is an Active Fiber Continuous Sensor (AFCS) that has high sensitivity for measuring Acoustic Emissions (AE) and strains in structures. Previous designs use electrodes that are above the piezoceramic substrate and a strong electric field is needed to couple the charge on the fibers to the external wiring circuit. The AFCS design uses rectangular fibers cast in an epoxy matrix in a configuration in which the top and bottom surfaces of the fibers are directly in contact with conductive epoxy which also bonds directly to a structural substrate, or to a kapton covering if the sensor must be electrically insulated from the structure. The conductive epoxy performs two functions, bonding the sensor to the structure, and forming the electrode of the sensor. The full electrode coverage and transverse poling is the simplest method of fabrication and this sensor design has been tested and shown to be very sensitive for measuring AE in composite materials and aircraft structures.
This approach reduces stresses in the fibers due to nonuniformity in the electric field where it enters the fibers, and interdigitated electroding allows the higher axial poling coefficient to be used, but this design also reduces the electrical and mechanical coupling efficiencies. The efficiency is not critical for structural actuation and control applications because large power amplifiers are used to drive the AFC. However, for sensing of AE this reduces the sensitivity of the sensor. This approach increases strain transfer between the structure and the sensing fibers and improves the detection of faint acoustic emissions in structures.