Do helicopter rotor blades speed up and down during the rotation?
A helicopter rotor usually has flapping hinges, which lifts the blade up when travelling forward and down when travelling backwards. The blade being at an angle indeed causes a change in effective moment of inertia: it would want to speed up when at an incline, and this would indeed cause a bending or warping moment were it not for..



..the Drag Hinge or lead/lag hinge. The image is from this site which contains an explanation on other rotor heads as well.