bl aded ▁off sh ore ▁wind ▁tur b ines ▁near ▁Z hu hai ▁in ▁ 2 0 1 3 . ▁ ▁Finally , ▁a est het ics ▁can ▁be ▁considered ▁a ▁factor ▁in ▁that ▁some ▁people ▁find ▁that ▁the ▁three - bl aded ▁rot or ▁is ▁more ▁ple asing ▁to ▁look ▁at ▁than ▁a ▁one - ▁or ▁two - bl aded ▁rot or . ▁ ▁Bla de ▁materials ▁▁ ▁In ▁general , ▁ideal ▁materials ▁should ▁meet ▁the ▁following ▁criteria : ▁▁ ▁wide ▁avail ability ▁and ▁easy ▁processing ▁to ▁reduce ▁cost ▁and ▁maintenance ▁ ▁low ▁weight ▁or ▁density ▁to ▁reduce ▁gravit ational ▁forces ▁ ▁high ▁strength ▁to ▁with stand ▁strong ▁loading ▁of ▁wind ▁and ▁gravit ational ▁force ▁of ▁the ▁bla de ▁itself ▁ ▁high ▁fat igue ▁resistance ▁to ▁with stand ▁cy clic ▁loading ▁ ▁high ▁st iff ness ▁to ▁ensure ▁stability ▁of ▁the ▁optimal ▁shape ▁and ▁orientation ▁of ▁the ▁bla de ▁and ▁clear ance ▁with ▁the ▁tower ▁ ▁high ▁f ract ure ▁t ough ness ▁ ▁the ▁ability ▁to ▁with stand ▁environmental ▁impact s ▁such ▁as ▁light ning ▁strik es , ▁hum id ity , ▁and ▁temperature ▁ ▁This ▁narrow s ▁down ▁the ▁list ▁of ▁acceptable ▁materials . ▁Met als ▁would ▁be ▁und es irable ▁because ▁of ▁their ▁vulner ability ▁to ▁fat igue . ▁Cer am ics ▁have ▁low ▁f ract ure ▁t ough ness , ▁which ▁could ▁result ▁in ▁early ▁bla de ▁failure . ▁Trad itional ▁polym ers ▁are ▁not ▁st iff ▁enough ▁to ▁be ▁useful , ▁and ▁wood ▁has ▁problems ▁with ▁repeat