Matching Items (2)
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- All Subjects: Mechanical Engineering
- All Subjects: sensing
- Creators: Neerukatti, Rajesh Kumar
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
The goal of this research is to couple a physics-based model with adaptive algorithms to develop a more accurate and robust technique for structural health monitoring (SHM) in composite structures. The purpose of SHM is to localize and detect damage in structures, which has broad applications to improvements in aerospace technology. This technique employs PZT transducers to actuate and collect guided Lamb wave signals. Matching pursuit decomposition (MPD) is used to decompose the signal into a cross-term free time-frequency relation. This decoupling of time and frequency facilitates the calculation of a signal's time-of-flight along a path between an actuator and sensor. Using the time-of-flights, comparisons can be made between similar composite structures to find damaged regions by examining differences in the time of flight for each path between PZTs, with respect to direction. Relatively large differences in time-of-flight indicate the presence of new or more significant damage, which can be verified using a physics-based approach. Wave propagation modeling is used to implement a physics based approach to this method, which is coupled with adaptive algorithms that take into account currently existing damage to a composite structure. Previous SHM techniques for composite structures rely on the assumption that the composite is initially free of all damage on both a macro and micro-scale, which is never the case due to the inherent introduction of material defects in its fabrication. This method provides a novel technique for investigating the presence and nature of damage in composite structures. Further investigation into the technique can be done by testing structures with different sizes of damage and investigating the effects of different operating temperatures on this SHM system.
ContributorsBarnes, Zachary Stephen (Author) / Chattopadhyay, Aditi (Thesis director) / Neerukatti, Rajesh Kumar (Committee member) / Barrett, The Honors College (Contributor) / Department of English (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
Composite structures, particularly carbon-fiber reinforced polymers (CFRPs) have been subject to significant development in recent years. They have become increasingly reliable, durable, and versatile, finding a role in a wide variety of applications. When compared to conventional materials, CFRPs have several advantages, including extremely high strength, high in-plane and flexural stiffness, and very low weight. However, the application of CFRPs and other fiber-matrix composites is complicated due to the manner in which damage propagates throughout the structure, and the associated difficulty in identifying and repairing such damages prior to structural failure. In this paper, a methods of detecting and localizing delaminations withint a complex foam-core composite structure using non-destructive evaluation (NDE) and structural health montoring (SHM) is investigated. The two NDE techniques utilized are flash thermography and low frequency ultrasonic C-Scan, which were used to confirm the location of seeded damages within the specimens and to quantify the size of the damages. Macro fiber composite sensors (MFCs) and piezoelectric sensors (PZTs) were used as actuators and sensors in pitch-catch and pulse-echo configurations in order to study mode conversions and wave reflections of the propagated Lamb waves when interacting with interply delaminations and foam-core separations. The final results indicated that the investigated NDE and SHM techniques are capable of detecting and quantifying damages within complex X-COR composites, with the SHM techniques having the potential to be used \textit{in situ} with a high degree of accuracy. It was also observed that the presence of the X-COR significantly alters the behavior of the wave when compared to a standard CFRP composite plate, making it necessary to account for any variations if wave-base techniques are to be used for damage detection and quantification. Lastly, a time-space model was created to model the wave interactions with damages located within X-COR complex sandwich composites.
ContributorsRajadas, Abhishek Chattopadhyay (Author) / Chattopadhyay, Aditi (Thesis director) / Neerukatti, Rajesh Kumar (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05