Prediction of Impact Contact Forces of Composite Plates Using Fiber Optic Sensors and Neural Networks

Real-time determination of contact forces due to impact on composite plates is necessary for on-line impact damage detection and identification. We demonstrate the use of fiber optic strain sensor data as inputs to a neural network to obtain contact force history. An experimental and theoretical study is conducted to determine the in-plane strains of a clamped graphite/epoxy composite plate upon low-velocity impacts using surface-mounted extrinsic Fabry-Perot interferometric (EFPI) strain sensors. The plate is impacted with a semispherical impactor with various impact energies using the drop-weight technique. The significant features of the strain and contact force response are contact duration, peak strain, and strain rise time. We have designed and built an instrumented drop-weight impact tower to facilitate the measurement of contact force during an impact event. The impact head assembly incorporates a load cell to measure the contact forces experimentally. An in-house finite-element program is used to...

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