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Title: Enhanced vibration damping materials and structures for wind turbine blades inspired from auxetic configurations
Author: Agnese, Fabio
ISNI:       0000 0004 5358 1902
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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An extensive analysis of the current applications and possible employments of auxetic materials and configurations is presented. These novel materials show a negative Poisson's ratio and, potentially, enhanced mechanical properties. Despite a substantial amount of publications can be found in literature about auxetic material properties, not many of these consider practical applications for them. Objective and novelty of this project is therefore the application of auxetic material and/ or auxetic inspired configurations to existing structures and in particular to wind turbine blades to modify their dynamic characteristics. Wind turbine blades are complex systems manufactured using polymer matrix composite materials and at present made of a combination of glass and carbon fibre · reinforced plastic (GFRP-CFRP). Total damping in a blade is a combination of aerodynamic and structural loss factors, the latter being related to the inherent damping of the material. The two fundamental modes of vibration related to bending are of flapwise and edgewise type. The structural damping is material dependent, therefore the amount of structural damping available for these two vibration modes is the same. However, for the flapwise mode, the aerodynamic damping plays a very important role for the overall modal damping r.atio, whereas for the edgewise mode the only damping mechanism present is the str.uctural one. As a consequence, only a low value of loss factor can be achieved in the edgewise direction. The first aim of this project is then to demonstrate how auxetic inspired structure can be successfully applied to increase the loss factor of the blade in the edgewise direction of vibration. To this end several solutions have been investigated starting from the utilisation of 3D auxetic foams. They showed an effective increase in loss factor but limited by the fact that at present these foams present a low stiffness. Other solutions considered macro composites with shaped fibres and a novel damper design. Both these solutions have been analysed and characterised either by FE analysis and laboratory testing.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available