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Composite and Adaptive Structures : Simulation, Experimentation and Modelling

Final Report Summary - CASSEM (Composite and Adaptive Structures: Simulation, Experimentation and Modelling)

The performance of passive and hybrid vibration control systems depends strongly on the viscoelastic material layer and piezoelectric material properties. In this project, numerical identification based on direct / inverse approaches will be developed. An advanced non-contact laser technique (ISI-SYS vibrograph system and Polytec scanning vibrometer) will be applied for the vibration measurements. These experimental data will be used to determine the natural frequencies and corresponding loss factors by the developed modal analysis program.

Another issue of this Sixth Framework Programme (FP6) project is to develop a general analytical and numerical (finite element) framework to model: (i) composite structures with piezoelectric sensors and actuators, (ii) thermal and pyroelectric effects in piezoelectric composites, and (iii) piezoelectric shunted damping.

In the context of the 'Composites and adaptive structure: simulation, experimentation and modelling' (CASSEM) project, we will also design a robust controller, which is stable in the presence of uncertainties of modelling and parameters, and ensures optimal disturbance rejection capability. In the implementation of the controller, actuators and sensors are needed. The locations of actuators and sensors over a structure determine the effectiveness of the controller in damping vibrations.

Results:
%:- A Plone-based virtual communication platform have been developed and used for the communication and co-ordination of activities among the partners. The following functionalities are accessible: access-control to the forum, structured work-space for exchange of electronic messages with management by topic-specific folders, shared electronic agenda, chat capabilities, structured work-space with management capabilities by topic specific folders for sharing and forwarding electronic documents.

- Database on the mechanical properties of multilayered composite materials, on piezoelectric and viscoelastic materials parameters the mathematical and experimental used methods. It covers the development, testing and verification of all methods of material testing by means of a large spectrum of sample materials.

- Database of the tested materials properties. The database is developed under Plone(R) management system which an open source content management built on the powerful object-oriented Zope application server.

- Inverse and direct approach used for the determination of viscoelastic and piezoelectric material properties. Different identification techniques are developed, tested and applied to characterise advanced composite material properties: elastic, plastic, hysteretic, viscoelastic, piezoelectric and dielectric. These techniques are based on indentation and vibration tests, and computation of effective properties on a so-called representative volume element. Future research needs are discussed in addition.

- Theoretical and finite element models for damped composite structure, and on the analytical and numerical methods for nonlinear vibration analysis and their validation. Modelling developments for frequency and temperature dependant VEM layer, of sandwich and laminated composites with VEM layers and of non linear vibration of damped sandwich and laminated composites as well as numerical validations of the all developed concepts will be investigated in this work package.

- Theoretical and numerical modelling of adaptive composite structures. This covers most of the work made by the various teams in the framework of the modelling of adaptive composite structures.

- Implementation of Matlab routines for uncertainties and development of reduced dynamic models. Methods have been developed for implementation of controllers in a Matlab-based environment, starting from a finite element model of a structure. The finite element model is first reduced using a Craig-Bampton technique. The model is then further reduced and translated into a state-space model which can be integrated in the Simulink environment. The Matlab / Simulink environment is suitable for the implementation of control routines. Examples of applications on a cylindrical composite boom equipped with macro fibre composite (MFC) actuators are presented.

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