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Dissertation
Guided plate waves and reflection factor for NDE of composite materials
Doctor of Philosophy (Ph.D.), Drexel University
1989
DOI:
https://doi.org/10.17918/00000465
Abstract
Traditional normal incidence, longitudinal wave mode inspection is fast turning into an old vanguard especially when faced with the realities of evaluating subtle material anomalies which degrade the performance potential of modern composite structures. In this research effort an oblique incidence reflection factor analysis and a guided plate wave approach are being adopted in an attempt to explore the potential of utilizing the abundance of ultrasonic wave modes and particle displacement types for the characterization of the material state in fiber reinforced composite structures. The generation and the propagation of guided plate waves in fiber reinforced composites are demonstrated to qualitatively and quantitatively evaluate material degradation problems such as delamination, porosity, fiber volume fraction changes, hydrothermal degradation and fiber mis-orientation. Several anomaly modeling techniques are coupled in order to describe material degradation in multi-layered composites. The global anomalies in the fiber reinforced laminates are modeled as changes in the effective elastic constants and density. The laminated plate theory is then used to smear the elastic properties over the whole composite structure thus enabling the modeling of different ply lay-ups. A new generalized model for plate wave dispersion in composite plates is introduced to establish the relationships between the material state and wave mode generation. The sensitivity of plate wave modes and several of its features capable of characterizing material state is demonstrated, using both experimental and theoretical evidence. The critical angles and resonant frequencies, which are also related to the existence of plate wave modes also reveal the possibility of using oblique incidence reflection factor analysis in the Non-destructive Evaluation (NDE) field. Another useful derivative from this research is the scientific proof for an increased sensitivity of the oblique incidence longitudinal and the oblique incidence shear waves mode to global anomalies such as porosity in fiber reinforced composite materials, a practical NDE tool.
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Details
- Title
- Guided plate waves and reflection factor for NDE of composite materials
- Creators
- Krishnan Balasubramaniam
- Contributors
- Joseph Lawrence Rose (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xiii, 186 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) [Historical]; Drexel University
- Other Identifier
- 991014970207204721