| Carbon fibre composite materials have been widely applied in engineering due to its high specific modulus and strength,as well as good thermal and electrical conductivity.Carbon fibre composite lamination has been applied to electro-thermal anti-icing or de-icing systems for large wind turbine blades and aircraft wings,which exhibits many advantages,such as good function-structure integration,high heating efficiency and excellent fatigue resistance.However,carbon fibre electro-thermal lamination often suffers damages during manufacturing,transportation and operation.Damages not only decrease the anti-icing and de-icing effect in cold environment,but also cause massive economic losses and even safety events.Therefore,to understand how the damages influence the electro-thermal performance of the carbon fibre composites and to repair the damages to restore the electro-thermal performance is of great importance.Considering the actual material system for wind turbine blades,the system of E-glass fiber fabric/epoxy resin and vacuum infusion molding process(VIMP)were used to prepare sample substrates.Hand lay-up process was utilized to prepare carbon fibre lamination on the substrates.All the damaged samples were made artificially,including penetrated damages and low-speed impact damages.And the damaged samples were homogeneously repaired by hand-up method with patches.In this work,a series of damaged samples were prepared according to the actual penetrate damages occurred during manufacture and transportation process.These samples were used to investigate the effects of penetrated damages on the electro-thermal performance under different ratios of hole diameter to sample width(D-W ratio).Results show that effect of D-W ratio to the electro-thermal performance exhibits non-linear feature.D-W ratio has significant influence on the temperature distribution and maximum local temperature.When D-W ratio reaches 0.625,electrical resistance increases from 0.746 ? to 1.927 ?,and maximum local temperature increases from 78 ?to 139 ? which exceeds the allowed temperature for composite materials.These damages are necessary to be repaired.The same carbon fibre composite materials were also adopted to repair a typical penetrated damage with diameter of 30 mm.Effect of lamination shape,size and thickness etc.on the electro-thermal performance were investigated.Results show that the best repairing effect are from the double-layered and square-shaped carbon fibre patches.This repairing type restores the electrical resistance from 0.913 ? to 0.654 ?,and local maximum temperature decreases by 30 ?.In this work,pendulum-dropping apparatus were used to simulate actual low-speed impact damages.Effect of different impact damages on the electro-thermal performance was investigated.Results show that impact energy leads to non-linear influence on electrical resistance.Furthermore,when impact energy becomes bigger,the electrical resistance increases more quickly.High temperature effect also occurs on the side of impacted position.When the impacting energy becomes higher,the local temperature differential amplitude becomes bigger.Maximum temperature differential of 17 ? was observed in the experiment.It indicates that electrical resistance,impacting appearance feature and thermal performance are all necessary to be considered to evaluate the effect of impact damage on the electro-thermal behavior due to the complexity of impacting damages.This work has been dedicated to evaluating and repairing the damages on carbon fibre electro-thermal composite lamination... |
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