Surface-mounted polymer piezoelectric transducers offer attractive design flexibility for guided-wave structural health monitoring (SHM), yet broadband methods for mode-selective Lamb-wave excitation remain limited. In this work, we investigate non-periodic annular P(VDF-TrFE) transducers for high-selectivity Lamb-wave transduction by combining analytical modeling, numerical optimization, and experiments. A line force model is first extended to concentric annular electrodes and assessed against fully coupled finite-element simulations and broadband measurements. The model is shown to capture the overall tuning behavior and to predict the peak and null frequencies of the two fundamental modes with good accuracy, making it suitable for fast design optimization. Based on this model, a broadband optimization framework is developed by minimizing the wave-packet energy of the undesired mode relative to that of the desired mode over the full tone-burst bandwidth. The optimized transducers achieve high selectivity with compact geometries, a small number of electrodes, and a single driving signal. The underlying mechanism is clarified by showing that the introduced non-periodicity clusters neighboring nulls in the source influence spectrum and creates an effective rejection band over a finite frequency range. Comparisons with conventional tuning and a phased-array approach further highlight design flexibility and robustness for various signal bandwidths. Experiments on two fabricated optimized transducers confirm the predicted selective behavior, although the measured suppression levels remain lower than the theoretical ones. These results provide a computationally efficient route to compact broadband transducer design for SHM applications.
Dong et al. (Tue,) studied this question.