Self-Healing Performance Comparison Between Two Promising Vascular Vessel Systems of the Wind Turbine Blade

Hollows produced by wires and borosilicate tubes are two significant approaches for the storage and transport of healing agent for self-healing wind turbine blades. To compare the performance for the two approaches, sheet samples and prototype blades were molded with vacuum-assisted resin transfer molding (VARTM) and max-flexural strength was evaluated before and after the self-healing process. One millimeter outer diameter with 0.5 mm inner diameter borosilicate tubes were used to store and transport the healing agent. Dicyclopentadiene was used as the healing agent and Grubbs' first-generation catalyst was used to initiate polymerization. To obtain the same structure of the tube, a lost-wax method was applied twice to form hollows with 1 mm outer diameter and 0.5 mm inner diameter. Since the samples need to be heated to form the hollows, the effect of the heating process on flexural strength was investigated. The flexural strength of the samples showed to be enhanced with the heating process. The percentage improval for flexural strength was 14.18% at 120 °C, 21.79% at 135 °C, and 10.89% at 150 °C. The growth trend continued until 135 °C and decreased after 135 °C. The toughness of the samples was also weakened. With the heating process, the initial and post self-healing flexural strength between samples with tubes and samples with hollows showed little difference. The recovery percentage of samples with tubes was 81.55%, while that of samples with hollows was 81.92%. Without the heating process, the initial and post self-healing flexural strength between samples with tubes and samples with hollows also showed little difference. The recovery percentage of samples with tubes was 89.52%, while that of samples with hollows was 89.46%. The space between the tubes/hollows greatly affected the flexural strength. The flexural strength of samples with a larger space between tubes/hollows was higher than that of samples with a smaller space between tubes/samples. For the prototype wind turbine blade, the initial and post self-healing flexural strength followed the same trend. For samples with hollows, the ratio of the inner diameter to outer diameter can be close to one so the walls can be very thin improving storage and transport efficiency.