Understanding Effects of Multiple Lightning Strikes on Pultruded Carbon Fiber Wind Blades

Abstract:
Lightning strikes continue to cause wind turbine blade failures and there are gaps in the understanding of the impact of high current exposure on blade materials. While blades are outfitted with lightning protection systems to direct current to ground, these systems occasionally fail and allow current to flow through the blade structure. This may occur many times over a blade’s service life, and carbon fiber is a particular concern due to its conductivity. To understand effects on pultruded carbon fiber wind blades over an estimated 20-year lifetime, lightning impulse testing was used to simulate multiple lightning strikes. A 22kV, 30 microsecond rise-time pulser was used on three specimens. The specimens were exposed to similar total cumulative charge transfer but a varying distribution of strike amplitudes. Subsequently, specimens underwent compression, tension, and short beam shear testing. Upon completion of additional structural testing, results will show the impact of multiple strikes and the effect of strike amplitude order.