Passive vibration control of aerospace structures based on viscoelastic materials

Abstract

In general it is very important to know the dynamic response of any structure submitted to loads and based on it to modify it mass, sti ness, or damping properties of the same one nally to obtain a desired response within a margins of safety considering the life of the structure. The damping properties of the structure were modi ed trough the use a passive damping to control the vibrations in structure with energy saving bene ts with regard to the active control and also for its facility of implementation reducing the probability of failure of the system. In the context of passive damping a variation of the loss factor was achieved based on the introduction of a viscoelastic material in a CFRP laminate structure by experimental tests using by bandwidth method. Cork was used as a viscoelastic material for its lightness and low relative price and showing a great potential in the aeronautical eld for vibration control in a high number of aeroelastic phenomena. The use of cork based composites can also be thought in space components in the form of sandwiches with cork cores or high performance ber reinforced composites with embedded cork dust aiming at minimizing the vibration occurrence of large structures, which must have high stability requirements in terms of displacement and rapid damping vibrations caused by any disturbance in the system. One most ambitious application of cork based composites refers to the structure of solar sails. This type of spacecraft only needs large sails and deployable booms that keep the sails deployed and support the the transmitted loads. Thus the study of the loads and vibrations that a ect the booms is very important. In the present case a passive damping using a design that comprises a viscoelastic material sandwiched between multiple CFRP layers was considered envisaging decreasing the amplitude of the vibrations in the boom induced by the operation of the AOCS. A computational analysis of this con guration of the material was developed using a nite element model (FEM) code to obtain the main dynamic properties of the structure, such as the natural frequencies and loss factors. Numerical results were validated through the comparison with the dynamic response of the material as obtained in experimental testing. Moreover, the improved damping properties found on cork based materials allow concluding that this type of viscoelastic material is a viable passive solution for vibration control with minimum penalties in the nal weight of the structure.