The damping behaviour of fibre-reinforced plastics (frp), which is very good in comparison to metals, is to be used for dynamic use in transport in AbsorpAdhesive project. The main goal is to develop and manufacture a car trailer made of pultruded frp profiles. The bonding between the different profiles serves as a further element in order to maximize the structural damping of the trailer. The project is realised by three research institutes and supported by a project-accompanying committee. Within the three research facilities, the entire process chain is examined, from bonding at coupon level, over the assemblies to the entire trailer (see figure 1).
IVW’s research focus is the investigation of the pultruded profiles’ damping behaviour, as well as the damping investigation of glued profiles. Starting with the investigation of the individual profiles, free oscillation tests were performed on the profiles. The decay process of the profile was recorded three-dimensionally, using an optical measuring system. The first natural frequencies of the specimens could be determined by a subsequent fast Fourier transformation. To validate these results, the respective test specimens were recalculated using a finite-element-analysis (FEA), and a modal analysis was performed. Figure 2 shows a comparison of FEA and experiment. The magnitude of the natural frequencies shows a very good correlation. The profiles’ damping behaviour was determined based on the free oscillations of the specimens using the logarithmic decrement.
In addition to the free oscillation tests, the damping behaviour of the material was determined using a dynamic mechanical analysis (DMA). The investigations were performed on both mat-reinforced and unidirectional-reinforced flat profiles. The results of these tests are summarized in figure 3. The samples were tested in a frequency range between 1 Hz up to 100 Hz. Furthermore, the load on the sample was varied, both bending and tensile tests were performed leading to the following results: The mat reinforcement leads to a higher damping value (tan delta ) than the unidirectional reinforcement. On the other hand, specimens with the unidirectional fibre orientation show lower damping in tensile test than in bending test. Both results are well compatible with the state of the art. With frp, most of the structural damping is caused by the matrix material. Accordingly, loads in which higher proportions of the load are taken by the matrix show a higher damping value than loads in which a large part of the load is taken over by the fibres. Both with the mat reinforcement and the bending load, the load on the matrix, and thus the damping of the material, increases.