2025 Volume 36 Pages 49-60
In this study, we investigated a method to visualize the stress state of a GFRP sheet we developed, focusing on the phenomenon in which the GFRP sheet changes in appearance from a transparent state to a white turbidity state under stress. Tensile and bond tests were conducted on the GFRP sheet. In the tensile test, the weft fibers became turbid in response to tensile stress. In the bond test, the warp fibers became turbid before debonding, and the weft fibers became turbid after debonding. We conducted verification experiments and inferred that the mechanism behind the opacification was the generation of cracks inside the fiber bundles due to tensile stress acting in the direction perpendicular to the fiber bundles. Digital image analysis was used to calculate the turbidity rate from the turbidity area of the GFRP sheet, and a high correlation between the opacity rate and strain was found in both the tensile and bond tests.
