Specific design of laminated composites regarding dynamic behavior by the application of local reinforcements

An approach for the specific design of laminated composites structures with local reinforcements regarding their dynamic behavior is presented. It is based on the sensitivity-based parameterization concept which has been presented in [1]. The search for best structural performance calls for a local adaption of the laminate properties to the inhomogeneous internal load distributions in order to take advantage of the anisotropic characteristics. If designing a structure regarding dynamic behavior, eigenfrequencies are often pushed above the essential excitation frequencies in order to prevent dynamic coupling. However, dynamic coupling can also be prevented by creating a resonance-free band in the range of the excitation source. Local reinforcements allow a specific shifting the eigenfrequencies for generating a resonance-free band. Different objective functions, which separate a pair of eigenfrequencies, are presented. A design solution is physically realized to verify the existence of a resonance-free band. A manufacturing process, called sequential curing process, is presented which allows the production of high-quality locally reinforced structures by separating the curing of basic structure and reinforcements into two temperature cycles. Eigenfrequencies and modes of the panel are measured with a scanning-vibrometer. The experimental results show high agreement with the simulation and the resonance-free band is confirmed.