April 25, 2008 by cimini
People from EMBRAER asked a question concerning the union between the
composite blades to the steel hub on the wind turbines. The question was:
"How the thermo-expansion between composites and steel is addressed on
the blade/hub connection?"
Slide 3 from Dr. Paul Veers' presentation showed a composite blade root
with a circular composite flange which includes what appears to be metallic
insertions for the fasteners. However, once attached to the steel hub, the
circumference of the blade will expand differently from the circumference of
the hub for an specific temperature variation. Is there any thermo-adjusting
coupling system?
These questions were addressed to Dr. Paul Veers and will be responded
soon.
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Here is the response of Dr.
Here is the response of Dr. Veers:
Carlos,
In reply to the questions on thermal effects,
Good question! I have never seen an analysis explicitly treating
thermal effects in the root. Expansion coefficients are different in
the steel and composite, but the entire root is highly constrained
by the steel hub and the bolting hardware. To the best of my
knowledge, the thermal effect is quite small compared to operational
loads.
Carlos A. Cimini Jr.
Visiting Scholar
Aero & Astro
Stanford University