I. Introduction
Modeling and characterization of 1-3 piezoelectric composite materials for the construction of 1-D, 1.5-D, and 2-D arrays are the subjects of extensive works for more than 15 yr. The first theoretical and experimental studies have essentially mentioned three main meehanical modes of vibrations: the thickness mode [1], which is used for the generation and the detection of the altrasonic beam; the radial modes [5]; and the lateral or spurious modes caused by the Bragg diffraction of transverse waves in the periodic microstructure [2] [4]. These resonances limit the upper frequency of good use of a composite pattern. Over the past, few years, the development of complete finite element 3-D models, with time or frequency domain analysis, has allowed the extension of these studies to the modeling of electro-acoustic performances of l-3 piezoelectric composite arrays [6] –[8] taking into account the periodicity of the material, the arrangement of ceramic rods in the composite matrix, the kerf geometry between array elements, the properties of kerf material filler, and all other construction parameters of the device. In this work, we will pay attention to the Lamb waves in a piezocomposite plate because these rnodes are at the origin of the acoustical Cross-coupling inside an array. The influence of cross-coupling on the electro-acoustic behavior of multi-element transducers has previously been discussed by several authors [9] –[11]. It is mainly responsible for anomalous behavior in the single-element radiation field pattern and the electroacoustic response of the array. As for the modeling of cross-coupling, the problem has essentially been treated through intensive computation using finite element approaches [6], [7], [12], [13]. This provides, of Course, a quantitative and sometimes accurate description of the element vibration. Aside from this computation effort, we think it is interesting to have a physical analysis also, which enlightens the phenomenons, even if it gives only a qualitative or semi-quantitative analysis. This is the point of view sustaining this work on acoustic cross-talk in a bare piezocomposite plate.