Experimental Study On The Mechanical Properties Of Pultrusion/winding GFRP Bars

In this thesis, the mechanical properties of GFRP bars were studied from a trinity perspective which combined production, test, and application. And all the works were based on the production line of pultrusion/winding GFRP bars, which belonged to Shandong Safety Industrial Co., Ltd..Firstly, the material components and pultrusion/winding process of GFRP bars were briefly introduced. Then three types of GFRP bars were produced, which could be classified into low, medium, high rank according to the strength. Correspondingly, the symbols 1#, 2#, 3# were adopted to represent the three types of GFRP bars.Secondly, the tensile property tests were conducted to 1#GFRP bars under different loading rates, the tensile property tests about size effect were conducted to 3#GFRP bars with different diameters, then the compressive property tests were conducted to 2#GFRP bars with different slenderness ratios, and last the creep property tests were conducted to 3#GFRP bars under different stress levels. The test results showed that:(1) The tensile strength rose gradually with the loading rate increased, while it declined steadily with the diameter grew; The compressive strength decreased reversely with the slenderness ratio went up; The creep ratio increased continuously with the stress level grew.(2) The tensile failure mode showed splitting failure solely, but the compressive failure mode evolved from shearing failure and splitting failure to bending failure with the slenderness ratio increased.(3) Both the tensile stress-strain curves and the compressive stress-strain curves showed a linear relationship, which represented elastic deformation, thus, it was concluded that the GFRP bars belonged to brittle material.(4) Under the same condition that loading rate was 2mm/min, the tensile strength of 1#, 2#, 3#GFRP bars were 491 MPa, 708 MPa, 1027 MPa respectively, and the tensile elastic modulus of 1#, 2#, 3#GFRP bars were28.5GPa, 31.0GPa, 48.1GPa respectively.(5) The compressive strength was lower, only about 37% of the tensile strength, while the compressive elastic modulus was approximately 1.1 times as high as the tensile elastic modulus; The creep strength was about 87% of the tensile strength.(6) The loading rate of 2mm/min and the slenderness ratio less than 20 were recommended to determine the tensile and compressive property indexes of GFRP bars, respectively.Finally, based on orthogonal test principle and FLAC 3D numerical simulation, the optimization design of tunnel support was conducted for the three types of GFRP bars above-mentioned, then the optimal support scheme was obtained; Meanwhile, it concluded that: the greater the elastic modulus, the better the advantage of high strength property of GFRP bars could be exerted.