Development of using PVDF films and Fiber Bragg Grating sensors in dynamic measuring technique
Date Issued
2015
Date
2015
Author(s)
Huang, Kang-Che
Abstract
This research is mainly focused on the development of dynamic measuring techniques using Polyvinylidene fluoride (PVDF) piezoelectric thin film and fiber Bragg grating (FBG) sensor. In regard to the transient behavior of cantilever beam, high sensitivity and pressure sensing ability are two key characteristics of PVDF film for acquiring force history of impact loading. After confirming the correctness of experimental boundary conditions, the impact loading history obtained from experimental measurement is used for Timoshenko and Bernoulli-Euler beam theories to investigate the transient responses. By comparing the theoretical and the finite element (FEM) simulation against measurement from corresponding experiments, this research is to discuss the ability of Timoshenko beam theory for calculating transient behavior under different slender ratios. Analyzing the wave propagation behavior on the edge of solid has been a changing problem with highly difficulty. This research propose the combination of coarse wavelength division multiplexing (CWDM) device with power modulated method to suppress dark current of photodiode and to realize multiple points dynamic measurement in high sensitivity. Based on the slender geometric characteristic of the optical fiber, FBG has great performance as a sensor for distinguishing the strain on the edge of an aluminum solid. In the perspective of dynamic behavior in time domain, three dimensional transient strains measured by pre-strengthen FBG sensors have great consistency with FEM simulation. Expansion and contraction of electrode particles during charge and discharge process causes large contact stresses, which leads to graphite electrode being fractured. An additional solid electrolyte interphase (SEI) is formed when the fractured graphite particles expose a fresh carbon surface to the electrolyte and the capacity of lithium ion battery is fading owing to the loss of available Li ion. With the combination of a high speed interrogator, advanced FBG sensors are embedded in graphite layer to deliver in-situ condition of temperature and strain. A miniature pressure sensor is arranged inside the top lid of battery to monitor the internal pressure variation in nominal usage. With these embedded sensors, the experimental results has the potential to evaluate the state of charge (SOC) and the state of health (SOH) of lithium ion battery.
Subjects
Polyvinylidene fluoride
fiber Bragg grating
impact loading history
finite element
Timoshenko beam theory
coarse wavelength division multiplexing
power modulated method
lithium ion battery
solid electrolyte interphase
state of charge
state of health
Type
thesis
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