Flexural Behavior of Biaxial (±45°) Non-Crimp Glass Fiber Composites: Influence of Test Rate and Laminate Thickness

This study investigates the flexural behavior of biaxial ±45° non-crimp glass-fiber composites manufactured with an unsaturated polyester resin matrix. Three-point bending tests were performed on laminates with different numbers of fabric layers and at several test rates, in order to evaluate the influence of laminate thickness and loading speed. The analysis included not only maximum flexural stress and strain, but also maximum force, time to maximum force, flexural modulus, displacement at maximum force and absorbed energy up to maximum force. The results showed that laminate thickness was the dominant factor controlling the bending response. The maximum force and absorbed energy increased strongly with the number of layers, while the displacement at maximum force decreased as the laminates became thicker. The maximum flexural stress became more dependent on thickness at higher test rates, whereas flexural strain and modulus showed weaker or more scattered trends. The post-peak response was highly irregular, reflecting progressive damage mechanisms typical of layered fabric composites. The obtained results indicate that thicker biaxial glass-fiber composites provide improved load-carrying capacity and energy absorption, which is relevant for lightweight marine structures and severe loading events.