Windmill Rotor Blade Failure (due to Lightning)  

Thread by Neil Smith on 23 Aug 2009 at 16:08:09 
Dear Platform (on Integrated Materials Simulation & Analysis):

From a report on Breakdown Risks in Wind Energy Turbines, I rephrase the following on Rotor Blade Damage: "Fibreglass rotor blades represent the most vulnerable component of a wind turbine. Lightning, Vibrations or contact with the tower can result in major damage to the blades. Design errors and manufacturing defects can also cause problems in the rotor blades during its operation. For example, blades can develop cracks at the edges, near the hub or at the tips. The possibility of the bolts breaking due to overload cannot be rules out either. Studies show that about 20% of the total damage due to lightning has occurred to the windmill blades".

Now also referring to the wind mill failure at the Lelystad A6 Motorway (see the news section on this site) my question is, if lightning is a potential root cause for failure of glass / carbon and resin based rotor blades, how is this prevented and my main point, what is the influence of diffused water in the rotor blade on the overall shock failure resistance? Could the effectiveness of a lightning receptor including drain passage be reduced by the presence of water in the polymer, fibre or between interfaces?

Could you back-up with calculations?

Thanks (also for this nice platform),
Neil

    Comment by Frank on 12 Jul 2011 at 11:49:15  | |responses: 1|
    This is a very interesting subject. Windmill blade lightning failure is often related to the presence of moisture inside the blade.

    The high temperature of the lightning can drive the accumulated moisture (so water in the microscopic phase, present at fibre interfaces or voids in the laminate) to a sudden steam expansion.

    Subsequent damage can be,
    -delamination,
    -burst bonding,
    -residue compromise,
    -longitudinal cracks,
    -trailing edge cracking,
    -detached blade pieces,
    -spar separation or partial or complete blade destruction.

    There is little rigorous (public) research available on this important subject. The developed CheFEM program seems particularly useful as a predictive tool in this regard.

    Best,
    Frank

      Comment by Neil Smith on 05 Sep 2011 at 21:01:09  | |responses: 0|
      Frank,

      Thanks for your comment; interesting and helpful.

      Regards,
      Neil