Tensile behavior of strain-hardening geopolymer composites (SHGC) under impact loading

Strain-hardening geopolymer composites (SHGC) exhibit remarkable ductility, crack control and high energy dissipation capacity when subject to quasi-static tensile loading. However, their mechanical performance under dynamic loading has not yet been explored. A comprehensive assessment of possible rate effects is required to facilitate a targeted material design for various practical applications. The article presents the results of an experimental investigation on the mechanical behavior of two types of SHGC under both quasi-static and impact tensile loading. The composites were reinforced with 2% of either short polyvinyl alcohol (PVA) fiber or ultrahigh molecular-weight polyethylene (UHMWPE) fiber. The experiments were performed both at the composite scale and at the fiber level. The impact tests on the plain geopolymer matrix and SHGC were performed in a gravity-driven split-Hopkinson tension bar (SHTB) at strain rates of up to 300s(-)(1). The tests were accompanied by optical measurements to assess specimen deformation and multiple cracking by means of Digital Image Correlation (DIC). The dynamic fiber-matrix bond properties were investigated in a miniature split Hopkinson bar. Both under quasi-static tensile loading and impact tensile loading, the SHGC made with UHMWPE fibers exhibited superior mechanical performance compared to the composite made with PVA fibers. When comparing the impact tensile performance of SHGC with normal-strength SHCC from previous studies, SHGC demonstrated higher dynamic tensile strength and energy dissipation capacity, making SHGC promising for strengthening/prospective applications against highly dynamic actions.