The composite structures embedding piezoelectric implants are able to modify their mechanical properties with respect to their environment (e.g. active vibration control), to interact with other structures (e.g. mechatronic) or with human beings (e.g. Human-Machine Interaction). Conventionally, to functionalize a mechanical device, the piezoelectric transducers are glued on the top surface of the structure and the power and control electronics are away. To protect the transducers and their electric connections and develop some industrial products in "plug and play" mode, it is necessary to be able to embed a wide distributed network of piezoelectric implants into the heart of the composite material during the manufacturing process of the products. However, if these adaptive structures are widely studied in the literature in a numerical point of view, there is no experimental research about the influence of the embedding parameters on the overall performance of the final structures. The idea of this study is to create a benchmark. In this paper, a set of beams (around 50 mm wide and 715 mm long) made of glass fiber composite with six plies (around 2.5 mm thick) are manufactured, with three piezoelectric elements embedded at a specific depth. This parameter is modified for each beam. At first, the material parameters of each beam are characterized, then a modal analysis is used to extract the key parameters of the final products. At the end, the different parameters and test results of each beam are compared and discussed.