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Vibrational and guided wave based approaches for quantitative NDE of adhesive composite joints
Adhesive composite joining technology attracts high interest due to its critical advantages for structural repair and integrated manufacturing of complex next generation composite structures. One of the main issues to be resolved for broader acceptance of this technology is robust nondestructive evaluation and certification of joints. ^ Existing NDE methods such as ultrasonic scanning and acoustic emission analysis have severe limitations in terms of cost, in-the-field or active interrogation capability, and data interpretation. The objective of this work was to study and analyze the applicability of vibrational and guided wave based methods for robust quantitative NDE of joints. ^ Natural vibration frequencies of adhesive joints with different cracks and boundary conditions were modeled analytically. Comparison of the results with numerical simulations and experiments showed generally insufficient sensitivity of the method for robust quantitative NDE. ^ Guided wave based method was extensively studied by dynamic finite element-simulations to provide better understanding of the wave propagation phenomena in cracked joints. Effects of actuator and sensor location, multiple sensors, and crack face contacts in joints were studied. An improved method based on mode decomposition using a HHT transform was developed and validated numerically and experimentally. It was shown that the method yields more robust crack data in joints. It was concluded that inexpensive guided wave based methods are suitable for embedded active real-time monitoring of composite joints. ^ Static and dynamic characteristics of a new laminated piezoelectric nanofiber composite sensor and/or actuator were simulated by finite element method as a function of lay-up. It was shown that the ultrathin piezoelectric laminated composites exhibited unique flexibility and tailorability of their deformation response that can provide qualitatively new opportunities for quantitative NDE. As an example, a possibility to detect the slope of the crack front in the joint was demonstrated.^ Overall, this research provides fundamental basis for the development of the next-generation inexpensive real-time NDE systems that can further promote and improve the acceptance of adhesive joining technology for primary structural applications. ^
Chen, Yong, "Vibrational and guided wave based approaches for quantitative NDE of adhesive composite joints" (2007). ETD collection for University of Nebraska - Lincoln. AAI3275064.