Tensile and compressive behavior of thermoset and thermoplastic GFRP bars

Fiber-reinforced polymer (FRP) bars are increasingly adopted to reinforce concrete members due to their physical–mechanical properties and durability. Usually, glass FRP (GFRP) bars comprising thermosetting resin are employed. However, bars comprising thermoplastic resin are also available in the market, although quite limited research was done to investigate their behavior. The contribution to the member capacity of GFRP bars in compression is generally neglected due to the limited research regarding their compressive behavior and to the absence of a shared procedure to obtain reliable indications of GFRP bar compressive properties. In this paper, the tensile and compressive behavior of thermoset and thermoplastic bars is experimentally studied. Three different diameters were considered for thermoset bars, while five diameters were considered for thermoplastic bars. The tensile test was performed according to ISO 10406-1, while a set-up previously adopted in the literature is used for the compressive test. For each bar, the tensile and compressive strength and tensile and compressive elastic modulus are measured. The bar axial strain is obtained with an extensometer or with digital image correlation (DIC). The results obtained show limited differences of tensile and compressive strength with varying the diameter for both thermoset and thermoplastic bars, while the tensile and compressive elastic moduli are approximately equal and independent from the diameter for the same type of bar. These are used to put forward the constitutive law for thermoset and thermoplastic bars.