Numerical optimisation of piezocomposite material properties using 3D finite - element modeling

1-3 connectivity piezoelectric ceramic composite materials are commonly used as the active layer of ultrasonic transducer arrays in many applications. In a typical design, the designer has a freedom to choose between various piezoceramic crystals and polymer fillers that constitute the piezocomposite structure. However, there are many design constraints to be met, including the requirements for uni-modality and low lateral coupling of this periodic material configuration. Additionally, recent developments in material science opened the possibility to adjust the polymer composition, and therefore its parameters, in a continuous
manner. Given such a complex design problem, it is convenient to use numerical
optimisation to meet the design constraints while maximizing performance. However, classic 1D transducer models, while quick to compute and suitable for optimisation, become inaccurate with these new polymer materials, as they require the use of simplifying assumptions.
In this work, a comprehensive time-domain 3D Finite-Element Model is presented which was designed for efficient computation, making it suitable for use with numerical optimisation. The model takes into account numerous phenomena that could not be modelled in 1D, such as non-uniform surface vibration, and inter-element crosstalk. Additionally, it permits optimisation of the filler polymer composition to maximize performance for the desired application. Results of the optimiser for an example 2.5MHz array design problem are presented and discussed.