root causes for early cracks in wind mill rotor blades

Thread by Dennis Alezzi on 24 Jan 2011 at 15:19:56 
Dear All:

With reference to the news topic on this site (cracks in composite rotor blades in Eemshaven), I am wondering what the root cause is for these unexpected mechanical failures in wind mill rotor blades. Is it caused by design flaws (incorrect FEM mechanical stress and strain models?), processing of the composite (too much moisture in the workroom, insufficient thermal epoxy curing), insufficient rigorous testing and regulations standards, unforeseen chemically driven ageing (moisture on the blade, alkaline aqueous solution, freeze cycles), etc.

As officially stated the technical lifetime of a blade should exceed 20 years, whereas the break-even point for most wind turbines is around 10-12 years. If, even in quite mild circumstances (on-shore Eemshaven, Germany), inspections show that cracks appear, what will be the status of the currently installed off-shore blades (I suppose these inspections are on a less regular basis because the locations are more complicated to access)?

Thank you for the followup.

Dennis Alezzi