Date of Award

2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Sundaresan, Mannur Dr.

Abstract

Structural Health Monitoring (SHM) seeks to develop systems for data collection, verification, and analysis to detect the potential for critical damage to occur in engineering structures. Composite panels are engineering structures that are susceptible to damages such as delamination and fiber breakage which greatly reduce the safety and performance of the structure. For composite materials that are widely used in aviation, early detection of such damage is important to prevent failure while the component is in flight. A common SHM method for damage assessment of composites is the Lamb wave propagation technique, whereby waves may be introduced into the composite panel via piezoelectric transducers. The propagating waves are measured after traveling through the region of interest to detect damage present in that region. Scanning laser vibrometry is a method often used to detect wave propagation patterns. The method is beneficial in that it is noncontact, nondestructive, and can be applied to virtually all geometries. Wave propagation patterns in composite panels are different from those seen in isotropic plates due to their anisotropy and the viscoelastic nature of the matrix materials. The use of a scanning laser vibrometer (SLV) to characterize wave propagation through a composite panel was explored in the present research. The characteristics of interest were the directionality of the propagating wave's amplitude, velocity, and attenuation. Thin lead-zirconate-titanate (PZT) actuators were bonded to an undamaged carbon/epoxy composite panel and pulsed to extract the wavefields using the SLV. Numerical simulations of the experiments were also performed to verify the results.

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