Abstract: Tensile mechanical properties and failure mode of GFRP bars was different from common engineering materials. By one-time tensile and cyclic tensile test on GFRP thread bars with different sizes and fiber content conditions, the relationship between apparent characteristics and the stress was observed, and stress-strain behavior of GFRP bars on the locations of 1/2 and 1/4 length was compared and analysed.It was found that cracks emerged near the sleeves when the stresses of GFRP bars reached a certain value, and developed to the central of bars with increasing stress. The cracks closed gradually as the stress decreasing before the failure of bars. Before failure, the cracks develop longitudinally and became jagged in shape.Failure property is between brittle and plastic failures.Strength analysis shows that GFRP bars with diameters of 20 and 25 mm had the maximum utilization efficiency.

Key words: glass fiber, composite, bar, mechanical property, failure mode