Research On Multi-scale Mechanical Properties Of Basalt Fiber Reinforced Plastic

Fiber reinforced polymers(FRPs) are widely used in structural strengthening because of its excellent performance. A in-depth study of multi-scale mechanical properties of FRP conduces to the disclosure of localized damage evolution within structures reinforced with FRP, by which a new structural reliability design theory can be erected, full considering the discreteness and failure characteristics of materials. The main work of this paper is as follows :(1) Material mechanical properties of basalt filaments with a gage length of 25 mm were investigated under quasi-static loading by utilizing a MTI miniature tester; Basalt yarn samples with different gage lengths(25, 50, 100, 150, 200 and 300 mm) were tested under quasi-static loading at a strain rate of 1/600 s-1 using a MTS load frame and samples with a gage length of 25 mm were tested under dynamic tensile loading at four different strain rates(40, 80, 120 and 160 s-1) and four distinct temperatures(25, 50, 75 and 100 °C) utilizing a drop-tower impact system.(2) BFRP was fabricated using vacuum assisted resin infusion(VARI). Single yarn BFRP specimens were tested under both quasi-static loading at a strain rate of 1/600 s-1 and room temperature(25 °C) by means of a MTS loading frame and dynamic tensile loading at four different strain rates(40, 80, 120 and 160 s-1) and six temperatures(-25, 0, 25, 50, 75 and 100 °C) utilizing a drop-tower impact system. In order to illuminate structural scale effect mechanism of BFRP, BFRP Sheet samples with 8 yarns were complementally tested under four different strain rates(25, 50, 100 and 200 s-1) and six distinct temperatures(-25, 0, 25, 50, 75 and 100 °C) using a servo-hydraulic high rate testing system.(3) Weibull statistics were used to quantify the v ariation in strength of basalt fiber and its reinforced plastic under different testing conditions and the obtained Weibull parameters can be used for engineering application. Additionally, tensile behavior of basalt yarn was successfully simulated by means of a numerical model incorporated with Weibull parameters of basalt filament.(4) Comparative analysis was conducted among mechanical behaviors and properties of BFRP, CFRP and GFRP, by which application prospects of BFRP were uncovered.The results manifested that the material mechanical properties of basalt fiber are dependent on gage length, structural scale and testing condition. Its tensile strength diminishes with increasing gage length and the structural scale altering from fiber to yarn, while increases with increasing strain rate.The mechanical behaviors of BFRP are influenced by structural scale, strain rate a nd temperature. Its tensile strength increases with increasing strain rate, but decreases with the structural scale altering from single yarn to multi-yarns and elevated temperature. Note that the energy dissipation capability of BFRP is superior to CFRP in spites of comparatively lower tensile strength, which can be attributed to its excellent deformability.