Advanced Modeling Techniques for Next-Generation Polymer-Based Acoustic NDT Transducers

Non-destructive testing (NDT) plays a vital role in assuring the structural integrity of aircrafts. As the use of metal-alternative materials like carbon fiber laminates becomes more prevalent, continuous monitoring and in-situ testing capabilities become increasingly important. This requires lightweight, low-power, low-cost and potentially flexible ultrasound transducers. Polymer-based Capacitive Micromachined Ultrasonic Transducer (polyCMUTs) can address these needs. PolyCMUTs are based on sub-millimeter sized drums with arbitrary arrangements, made from micromachined polymer layers. This offers a small form factor, rapid fabrication (~1 week) and highly customizable designs. To guarantee that the transducers meet the requirements, we employ extensive theoretical analysis and performance modeling. This work will present currently applied modeling and analysis techniques (analytic, numeric) of ultrasound transducers, with a focus on polyCMUTs. In more detail, we will introduce a modeling framework based on combining results from finite-element analysis (FEA) with much faster numerical methods. Validation with full-sized FEA and measurements showed less than 7% average deviations in terms of sensitivity, center frequency and bandwidth, requiring less than 1% of the computation time. This enables the rapid exploration of the vast design space of micromachined ultrasonic transducers to tune the performance to application specific requirements. In addition, the modeling results provide a firm guidance for characterization and quality control to streamline development and design optimization. Hence, the presented approach provides a key tool in the rapid realization of next-generation ultrasound transducers for NDT.