PIEZOELECTRIC FIBER COMPOSITE STRIP HEALTH MONITORING SYSTEMS BASED ON ULTRASONIC GUIDED WAVES

Open Access
Author:
Li, Sheng
Graduate Program:
Engineering Mechanics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 22, 2011
Committee Members:
  • Clifford Jesse Lissenden Iii, Thesis Advisor
Keywords:
  • structural health monitoring
  • piezoelectric fiber composite transducer
  • guided waves
Abstract:
The reliability of engineering structures is a constant maintenance concern. Improved operations call for Structural Health Monitoring (SHM) to accurately characterize damage and predict remaining life, thereby minimizing operating costs and risk. This SHM system concept relies on the integration of smart materials, like piezoelectrics, with the host structure enabling adaptation of Non-destructive Evaluation (NDE) methods such as the use of ultrasonic guided waves for SHM. This work focuses on the design of transducers to generate planar ultrasonic Lamb waves for damage detection, location, and characterization in plate-like structures. Comb-like strip transducers comprised of Piezoelectric Fiber Composite (PFC) are investigated, which have better structural integrity and tailorability than bulk piezoceramics. Strategic placement of these transducers enables damage monitoring over a large area for a variety of structures. Many factors including fiber orientation, fiber volume fraction, poling direction and electrode location are considered for these PFC transducers. Piezoelectric and mechanical properties for these innovative transducers are estimated through micromechanical modeling. A new Finite Element Analysis (FEA) employs co-simulation using ABAQUS Standard and ABAQUS Explicit together to simulate transient wave propagation from a PFC comb type strip transducer into a plate. The benefit behind this co-simulation analysis is to couple multiphysics (piezoelectric) analysis with transient dynamic (wave propagation), which is not possible with the two codes individually. Finally, trial experiments using PFC transducers for exciting planar Lamb waves that interact with damage such as corrosion, cracks and holes are also conducted. This experiment employs a laser vibrometer to visualize the wave propagation and is compared with FEA animations with unwanted reflection absorbing boundary conditions. The approach combines infinite elements with viscous surface pressure and is verified as an efficient way to remove edge reflections in 3D wave propagation problems.