Effects of the transfer function evaluation on the impact force reconstruction with application to composite panels

The determination of a reliable transfer function for force reconstruction of impacts on composite panels is addressed in the paper. The reconstruction of the impact force history requires the knowledge of the transfer function which relates the response to the contact force. In this paper, a new method to determine the transfer function of a composite plate, instrumented with surface bonded piezoelectric sensors, is proposed. Impact tests are carried out and the data are used to evaluate the transfer function. The force reconstruction results, obtained by using the new transfer function, are compared with the results obtained with the classic approach. Significant improvements are observed in predicting the force history, particularly when large deflections are present; these are quantifiable as an out of plane displacement of the same order of magnitude as the thickness of the plate. The influence of increasing the impact velocity, with the related increase in the contact force, is also studied. The proposed method provides good results over a range of impact velocities. Multiple impacts were also investigated and the method could correctly reconstruct force histories of consecutive impacts.