Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
Effect of acid attack on thermal degradation and complex electromagnetic parameters of CF/Ni fabric applied on wind turbine rotor blades
Submission Author:
Daniel Silveira , SP
Co-Authors:
Daniel Silveira, MICHELLE LEALI COSTA, Mirabel Rezende, Edson Cereja
Presenter: Daniel Silveira
doi://10.26678/ABCM.COBEM2017.COB17-0186
Abstract
Increase in energy global demand and environmental awareness push boundaries for the use of renewable resources. Wind turbine rotor blades, while in rotation, present large radar cross section, interfering in radar signals and depreciating the quality of navigation and communication in airspace. Aiming to eliminate such impacts, wind turbine rotor blades are developed using radar absorbing structures (RAS). Beyond structural properties, RAS may convert electromagnetic energy into heat, reducing spurious radiation and associated interference. In this work, carbon fiber nonwoven veil metallized with nickel (CF/Ni), possible precursor material used in RAS applied in wind turbine rotor blades, was submitted to acid attacks aiming reducing its reflector behavior in the X-band region of microwaves. Effects of acid attack on thermal degradation and electromagnetic properties of the CF/Ni veil were evaluated. Thermogravimetric analyses (TGA) in dynamic mode were performed in oxidative (air) and nitrogen atmospheres. Complex permittivity (εr = ε’ - jε”) and permeability (µr = µ’ - jµ”) of CF/Ni veil were measured by means of a vector network analyzer in X-band (8.2 to 12.4 GHz). Results show that thermal degradation profiles of the veil are maintained after acid attack, with equal number of major degradative events. However, changes in DTG peaks are observed in both atmospheres, associated with different weight loss rates. Already, the acid attack caused minor changes in electromagnetic behavior of CF/Ni veil, with a slight reduction of reflector behavior. High values of permittivity and close to unity average permeability (µ < 1) confirm the dielectric behavior of veil with reduced interaction with the magnetic field of microwaves (X-band). Electromagnetic results indicate necessity of aerial weight (g/m2) reduction and/or application of frequency selective surface (FSS) technique on the CF/Ni veil, enabling application of the studied material as absorbing layer in wind turbine rotor blade manufacturing.
Keywords
thermal degradation, CF/Ni nonwoven fabric, permittivity, permeability, wind turbine rotor blades
