Analytical and experimental study of embedded damping elements in composite

In this project, embedded viscoelastic elements for sandwich structured composites were modelled and optimized, in order to improve the acoustical and vibration performance of these structures. In the transportation industry, controlled vibration levels are required to provide passenger comfort, to increase vehicle life span, and to reduce maintenance costs. Vehicle performance, eligible weight gain and fabrication method criteria must be respected in the design of vibration treatments. The purpose of this paper is to investigate an analytical model for composite beams with internal viscoelastic layer damping. All analyses and tests were performed on beams in a clamped-free configuration. The equations of motion of the system were obtained using Lagrange's equations and were converted in the frequency domain using a Fourier Transform. The transfer function was obtained by solving for frequency displacements using the assumed modes method. Damping was quantified from the half-power bandwidth method. The first three transversal modes were considered to quantify the damping gain and the vibration attenuation with respect to a reference laminate. A parametric study was conducted using Matlab, in which various geometries and locations of the damping elements were tested. Added mass and surface coverage were additional controlled parameters. An experimental validation was conducted to confirm the validity of the analytical results. In these experiments, the viscoelastic elements were located at three different positions along the longitudinal axis of the beam. Two different configurations for the laminates were also evaluated. Impact tests were used to validate the transfer functions obtained from the model. The results showed a significant improvement of the damping with the embedment of the viscoelastic elements for some of the configurations. Partial coverage is shown to be effective and weight efficient. These general results will serve as a guideline for further studies implying plate or shell sandwich structures.