Macro-composites with star-shaped inclusions for vibration damping in wind turbine blades

The work describes the numerical and experimental assessment of using biphase composite structures with non-classical shape inclusions. Star-shaped biphase cells have been designed, modeled and tested to evaluate the complex engineering constants corresponding to various deformation modes. A Finite Element homogenisation method using the complex modulus approach has been used to evaluate the variation of the storage moduli, loss factors and amounts of strain energy dissipated in the matrix versus the unit cell geometry parameters. Experimental results have been obtained on aluminium/cast epoxy sample using a shear dynamic test rig and a dynamic mechanical analyser. The results have been benchmarked against unit biphase composite configurations with cylindrical inclusions having the same contact surface between inclusion and matrix than the star-shaped reinforcements. The composite cells are intended for a possible use as structural damping units to be located in maximum nodal strain positions corresponding to specific wind turbine blade modes.