Available at: http://digitalcommons.calpoly.edu/theses/1377
Date of Award
MS in Aerospace Engineering
In recent years composites have progressively been used for large-scale structures such as aircraft, ships, ground vehicles, and wind turbine blades. Traditional Nondestructive Evaluation (NDE) techniques have various limitations in assessing the performance of the large-scale composite structures. For instance, many techniques have the ability to measure either global or local properties but cannot measure both simultaneously. Nondestructive vibration detection techniques present a potential solution for evaluating both local and global large-scale composite structures, which are largely based on the fact that damage in a structure influences its dynamic characteristics such as modal parameters and Frequency Response Functions (FRF).
This study investigates locating delamination in composite laminate plates under dynamic loading utilizing accelerometers during dynamic response as an alternative structural health monitoring method in composite structures. The test specimens were manufactured using unidirectional carbon fiber/epoxy creating 11 cross-ply composite laminate plates with [0,90,0,90]s orientation. Delaminated regions were placed at one inch increments, horizontally along the specimen.
During testing, one side of each composite laminate plates were clamped using a custom fabricated fixture, cantilevered leaving the remaining edges free. An Unholtz-Dickie shake system excited the specimens. Dynamic response measurements using teardrop style piezoelectric accelerometers were taken along the surface face of each specimen, individually located along a 3 X 10 grid. Each response was compared collectively to examine any acceleration differences and damping between specimens. Finite element Modeling (FEM) ensured correlation of the flexural bending mode shapes between theoretical, analytical, and experimental. It was found that, the comparison between the results of the theoretical, Finite Element Analysis, and experimental data were in good agreement and delamination can be detected.