The Mars Reconnaissance Orbiter Mission
- Paper number
IAC-04-Q.3.B.01
- Author
Mr. James Graf, Jet Propulsion Laboratory, United States
- Year
2004
- Abstract
One of the most important theme of the structural analysis is the vibration reduction. At the present day there are different devices which can be used to improve structural damping based on the use of active or passive dampers. Many studies on reduction and/or suppression of vibrations in LFSS and SFSS (Large/Small Flexible Space Structure) are conducted in last decades. Different techniques can be used for vibration suppression, the most interesting are the ones based on the use of piezoelectric sensors and actuators, embedded into a passive structure, able to provide the necessary authority to reduce its elastic vibration. Such structures name also intelligent or adaptive structures are generally thin shells equipped with piezoelectric laminae. These laminae are made up of piezoelectric materials such a zirconate titanate (PZT) and are capable of transducing electric fields into mechanical strains and mechanical strains into electric charges. The active laminae are used actuate shell by inducing strains in non piezoelectric passive laminae and to sense deflections in the shell by measuring the local strain field. In this work a special smart structure will be proposed for vibration suppression of composite panels. In particular the viscoelastic properties of a composite panel-structure will be changed opportunely in order to modify the elastic damping characteristics of the material which constitute the panel. It is well known that these viscoelastic material are characterized by the complex modulus defined as E(T,ω)=E’(T,ω)+jE’’(T,ω). These moduli depend on to main parameters, the temperature T in which that material operates and more interesting on the magnitude of the oscillating frequency ? at which the composite structure can be subjected under a dynamic environment. In this study the determination of the complex modulus and the effect of above mentioned parameters on a composite panel for space applications are investigated. The sandwich panel is here made up of two carbon fibre skins and a polymeric core in analyzed. This core is constituted by an epoxy adhesive containing some silver conducting stripes opportunely distributed inside it. By applying a voltage to the ends of the silver stripes it is possible to produce a current which in turn gen-erates heating the epoxy resin and carbon skins by Joule effect. The temperature acts on chemical bonds increasing the molecular mobility producing relaxation of the material which in turns varies the mechanical and thermal characteristics of the core and the resin matrix reducing the storage modulus E’ and increasing the loss modulus E’’ and the loss factor η=E’’/E’=2ζ. It’s worth to note that this loss factor is directly related to the damping ratio of the panel. The viscoelastic parameters of the adhesive and of the carbon fibre will be experimentally estimated and evaluated using DMTA (Dynamic Mechanical and Thermal Analysis) and a TG/DTA (Thermogravimetry/Differential Thermal Analysis) tests. Mathematical models and finite element simulations of this Heated Damping Sandwich Panel (HDSP) will be presented in order to study the coupling related to the thermal and structural interaction between the core, the skins and the silver electrical conductors. The stripe’s cross section, the geometrical in-plane dis-position and the electrical feeding will be find in order to have the minimum transitory time or the mini-mum necessary power for vibration suppression.
- Abstract document
- Manuscript document
IAC-04-Q.3.B.01.pdf (🔒 authorized access only).
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