Microcosmic Mechanism Investigation on Lightning Arc Damage of Wind Turbine Blades Based on Molecular Reaction Dynamics and Impact Current Experiment

PVC and balsa wood are usually used in the interlayer structures of wind turbine blades. In this paper, a comparative study on the lightning damage characteristics of the two materials was carried out by molecular dynamic simulations and impact current experiments. The simulations show that the glycosidic bonds in cellulose break first, which leads to a strong decrease in the degree of polymerization (DP) of cellulose (while the DP of PVC changes irregularly), then C-O bonds in the pyranoid ring break and the main chain of cellulose is destroyed, producing small molecule fractions and a lot of gas molecules. There are two steps in the pyrolysis of PVC. H and Cl atoms fall off the main chain and combined for form HCl, which needs less energy and occurs earlier than cellulose pyrolysis at 2000 K, but cellulose generates more gas products than PVC at the same temperature. Thus the damages to balsa wood and PVC mainly appear as fiber fractures and pore extension, respectively, which are consistent with the morphological features of the damage to the two materials in the impact current experiments. The experimental results also show that the pyrolysis temperature of PVC was lower than that of balsa wood, and the residual strength decreases faster in PVC than in balsa wood with the increase of peak current. This study should play an important guiding role for lightning protection and material selection of wind turbine blades.