Damage mechanism of PVC and balsa wood used in wind turbine blade under thermal effect of lightning strikes

At present, PVC and balsa wood are usually adopted in the sandwich structure of the wind turbine blade. However, comparative research on the damage characteristics of the two materials under lightning arc is seldom reported. Large current experiment was conducted on PVC and balsa wood, which indicated that under the surge current, there was a more severe reduction in the residual strength of PVC than balsa wood. By the means of molecular reaction dynamics, the chemical reaction process, gas generation characteristics and water motion of the materials were studied quantitatively. As is shown in the visual results, cellulose (main component of balsa wood) was gradually splitting with the degree of polymerization(DP) reducing as time increasing, while there is no obvious change on the DP in the PVC aspect. The degradation of cellulose generated relatively more kinds of small-molecule gases while PVC mainly produced HCl and small amounts of olefins, but the number of gas products from PVC pyrolysis was far much more than that of cellulose. In addition, with many -OH. H and O included in cellulose, there are more H
₂
O molecules absorbed on the cellulose by H bond, which results in a large amount of water content in balsa wood, while, the density of H bond between PVC and water was much lower. Water around the surface of cellulose would turn into vapor that would expand when heated, making it a key factor to the damage of cellulose.