Effect of Dehumidification Treatment of Raw Materials on the Interlayer and Interface Properties of Polyurethane Composites Prepared by Vacuum Infusion and Mechanism Analysis

Polyurethane resin is widely used in the field of wind turbine blades due to its excellent toughness, rapid curing, and mechanical properties. However, its isocyanate component is easy to react with water to form CO 2 bubbles, resulting in pore defects and performance degradation. In view of this problem, this paper mainly explores the influence mechanism of different dehumidification times of raw materials on the interlayer and interface properties of glass fiber‐reinforced polyurethane composites by vacuum infusion. The results showed that the viscosity of the resin increased (gel time was shortened) after defoaming treatment, which still met the requirements of the vacuum infusion process. Compared with the sample without dehumidification, the interlaminar peel strength of the composites after dehumidification increased by 85.2%. After 4 h of dehumidification, the interlaminar shear strength reached 47.5 MPa (+38.1%), and the interfacial shear strength increased to 72.5 MPa (+132%). The microstructure analysis showed that the porosity of the laminates without dehumidification was relatively high at 6.56%, which decreased to 1.09% after dehumidification for 4 h. As the dehumidification time extended, the bonding between the matrix and fibers significantly improved. The cross‐section of the non‐dehumidification sample showed matrix breakage, and fiber pull‐out appeared at the fracture after dehumidification.