Cost-effective and reliable damage detection is critical for the utilization of composite materials. This thesis presents the conclusions of an analytical and experimental survey of candidate methods for in-situ damage detection in composite materials. Finite element results are presented for the application of modal analysis and Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage. These results were then verified experimentally by using piezoelectric patches as actuators and sensors for both sets of experiments. The passive modal analysis method was reliable for detecting small amounts of global damage in a simple composite structures. By comparison, the active Lamb wave method was sensitive to all types of local damage present between the sensor and actuator, provided useful information about damage presence and severity, and presents the possibility of estimating damage type and location. Analogous experiments were also performed for more complex built-up structures such as sandwich beams, stiffened plates and composite cylinders.
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