Dynamic mechanical properties and failure mechanism investigation of multiscale toughened basic magnesium sulfate concrete

Abstract

The dynamic impact compressive properties of a novel whisker composite material (i.e., ultra-high toughness basic magnesium sulfate cement concrete, UHTBMSC) is investigated in this study. First, X-CT and scanning electron microscopy are used to characterize the three-dimensional distribution characteristics of two types of fibers in the UHTBMSC, as well as the microstructure. Second, the Hopkinson compression bar technique is used to investigate the dynamic impact compression behavior of UHTBMSC under different strain rates. Finally, a novel 3D random packing model of steel fibers (straight and hooked) is established, and the 3D mesoscopic numerical simulation of the dynamic impact compression behavior of UHTBMSC is performed. The results show that the steel fibers are crossed and evenly distributed in the UHTBMSC matrix, whereas needle-rod-like 5–1–7 whiskers appear in large quantities in the UHTBMSC. Dynamic impact compression results show that UHTBMSC is a rate-dependent material, and a mathematical relationship between strain rate and dynamic increase factor is established for UHTBMSC materials. The numerical simulation results agree well with the test results, indicating that the newly established 3D meso-model can be used to effectively analyze the dynamic compression mechanical behavior of UHTBMSC. In addition, the results confirm that UHTBMSC exhibits excellent resistance to dynamic impact compression, which is primarily attributed to the crack inhibition effects of 5-1-7 whiskers and steel fibers, thereby effectively improving the dynamic mechanical properties of UHTBMSC.