This thesis focuses on the implementation of Electrical Resistance Tomography (ERT) as a structural health monitoring (SHM) technique for monitoring damage and strain in carbon fiber-reinforced polymer (CFRP) composites. In order to hone the ERT technique for two plain weave carbon/epoxy laminates, a cross-ply and a transversely isotropic laminate, were evaluated in a damage sensitivity study. The sensitivity study focused on the detection of thru-hole damage by comparing the voltage responses from different current amplitudes and injection patterns. The reconstruction quality and thru-hole detection showed a strong dependence on the fiber-directions relative to injection patterns. As a result, a different pattern was selected for each of the laminates, which were used in subsequent ERT tests. Stress concentration specimens were introduced and evaluated with ERT and digital image correlation (DIC) to observe the piezoelectric response of the composite coupons. With the introduction of DIC, best practices were exercised through the testing of fiberglass/epoxy open-hole tensile coupons to define the performance characteristics of a low-cost DIC system. Under tensile load the stress concentrations (open-hole and side-notch) provide predictable regions for focused strain intensity allowing for a preceding understanding of the full-field strain pattern. The results from the combined ERT-DIC tests indicate a strong correlation to conductivity loss in the regions of highest longitudinal strain as indicated by the full-field strain plots. ERT is presented as a viable low-cost method for SHM in CFRP composite structures where the piezoresistive carbon fibers can be used to self-sense damage and stress concentrations under loaded conditions.
|Advisor:||La Saponara, Valeria|
|Commitee:||Cheng, Lijuan (Dawn), Davis, Cristina|
|School:||University of California, Davis|
|Department:||Mechanical and Aerospace Engineering|
|School Location:||United States -- California|
|Source:||MAI 57/05M(E), Masters Abstracts International|
|Subjects:||Aerospace engineering, Mechanical engineering, Materials science|
|Keywords:||Cfrp, Composites, Digital image correlation, Eit, Electrical resistance tomography, Shm|
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