Study on the dynamic fracture characteristics of red sandstone composite under stress waves

To investigate the composite dynamic fracture characteristics of red sandstone under the action of stress waves, the impact loading experiment was carried out by using separated Hopkinson press bar, digital image technology and on the three-point bending specimen of semicircular disc with prefabricated cracks, to analyse the effects of loading rate and wavelength on the dynamic tensile and fracture characteristics of red sandstone. The results show that: ①the loading rate of red sandstone specimens has a primary function relationship with the dynamic tensile strength, fracture toughness and damage rate; the fracture energy increases by 415.27 % with the increase of loading rate. ②With the increase of wavelength, the dynamic tensile strength increased by 742.14 %, of which the fracture energy increased by 54.49 %, but the energy absorption rate showed a decreasing trend; the average speed of crack expansion increased by 4.09 %, and there is a hysteresis phenomenon in the time of strain growth of the first and last cracks; the effect of growth of the damage rate was strengthened. ③The strain at the first and last monitoring points of the main crack of the specimen increased by 84.31 % on average when the impact velocity was 8m/s.