Effect of Ultrathin Glass Fiber/Epoxy Prepreg Layers on the Strength and Toughness of Unidirectional Laminated Composites

Unidirectional glass fiber/epoxy laminated composites, typically manufactured by hot-pressing multilayer prepregs, serve as essential structural materials in wind turbine blades and for reinforcing tower structures. Ultrathin plies can enhance the design flexibility of this material, yet how their use affects strength and toughness remains insufficiently clear, making this a topic of significant research value. This study, unidirectional glass fiber/epoxy composites of identical thickness were fabricated using 20, 24, and 28 layers of ultrathin prepreg. The variation and mechanisms of their strength and toughness with layer number were systematically investigated. The results show that the strength and toughness of unidirectional laminated composites are significantly affected by anisotropy, with performance differences reaching over 35 times. The increase in the number of prepreg layers will enhance the fiber volume fraction of the composite, thereby improving the interlaminar mechanical properties of the unidirectional laminated plate, and ultimately determining the change in its overall mechanical performance. When the fiber volume fraction increased from 39.3% to 55%, the flexural strength and impact resistance of the composite increased by 73.2% and 59.2%, respectively. This study provides valuable theoretical guidance for the on-demand design and performance optimization of composites.