Mechanical Properties and Endurance Limit of Fiber Composite Bars

Abstract

Experiments were performed to understand the mechanical properties and endurance characteristics of deformed glass fiber reinforced polymer (GFRP) rods.

Mechanical properties analyzed included tensile strength and modulus of elasticity. GFRP rods with vinylester matrix and GFRP rods with a polyester matrix were tested in tension and compared. The #4, #5 and #6 vinylester bars showed ultimate strength capacities of 70 ksi, 70 ksi, and 96 ksi and moduli of elasticity of 4.9, 5.3, and 6 million psi, respectively, based on cross-sectional areas assumed for steel rebars of the same size number. The ultimate strength of polyester rods average 85 ksi for the #4 sizes, 70 ksi for the #5 sizes, and 96 ksi for the #6 sizes; all calculated based on equivalent steel area. The #4, 5 and 6 polyester rods showed modulus of elasticity of 5.12, 4.85, and 5.11 million psi respectively.

Endurance testing of ten specimens (only vinylester matrix rods) of each size bar at varying percents of their ultimate load capacity from 50% to 10% indicated a definite increase in number of load repetitions to failure with reduced stress. However, the thirty tests done were not sufficient to indicate a definite endurance limit for the GFRP bars.