Evaluating the Mechanical Properties of Fiberglass-reinforced Polymer Bar

Abstract

This study examined the mechanical characteristics of glass fiber-reinforced polymer (GFRP) bars following its introduction in the Ghanaian construction industry. Tensile strength, tensile failure strain, and modulus of elasticity for different GFRP bar diameters were examined. The specimens were investigated according to the provisions in the British Standards. To conduct the tensile strength test on the GFRP, a gripping technique was required to prevent slippage or premature failure. The gripping mechanism comprised a circular steel pipe with an inner diameter of 22mm and 150mm long for gripping on both ends of the specimen where 150mm long of the GFRP bar was implanted into the steel pipe, leaving 300mm of free length. Thus, an appropriate embedment length and adequate pipe size were crucial components in this kind of gripping device. An epoxy mixture with expanding additives and high-strength non-shrink was used to fill the area between the steel pipe and the bar. The GFRP bar sizes used in this test were 10mm, 12mm, and 16mm and their tensile strength from the test results were 1193 N/mm², 1030 N/mm², and 866N/mm² respectively. The modulus of elasticity of the fiberglass also varied for the10mm, 12mm, and 16mm as 54434 MPa (N/mm²), 41711 MPa (N/mm²), and 30516 MPa (N/mm²) respectively. The ultimate strain for 10mm, 12mm, and 16mm was 2.20%, 2.48%, and 2.8% respectively. The measured values of ultimate strength, failure stresses, and axial tensile modulus correspond well with the values published in the relatively limited available literature. From the experimental data, the stress-strain relationship for all bar sizes was a single monotonic straight line. Thus, failure of the bars occurred suddenly without the warning that is usually associated with ductility beyond ultimate/maximum stress. Compared to conventional steel, fiber-reinforced polymers are highly robust and lightweight. Its mechanical properties, however, are linear elastic and lack a prominent yielding stage, which lowers the rates of elongation and failure strain. Furthermore, GFRP usually has a lower elastic modulus than steel, and unlike steel is non-homogeneous and an-isotropic.