The effects of tensile strain rate on the dynamic tensile behavior of ultra high toughness cementitious composite

In this study, dogbone-shaped block specimens with cross section aspect ratio of 1.25 were prepared and tested at different strain rates ranging from 10-5 to 10-1 s- 1 to investigate the dynamic tensile behavior of ultra high toughness cementitious composite (UHTCC) under different strain rates. The dynamic tensile responses were characterized in terms of the tensile strength, strain capacity, elastic modulus, specific energy absorption (SEA) and crack pattern. The results indicated that, with the increase of strain rate, the ultimate tensile strength increased by 160% but the strain capacity decreased by 80%. As the strain rate increased from 10-5 to 10-2 s-1, the elastic modulus and SEA increased by 40% and 50%, respectively. Reduction in the width of cracks in UHTCC was observed with the increase of strain rate while the number of cracks kept almost constant. Compared with thin planar specimens, the rate of increase in the ultimate tensile strength of UHTCC block specimens caused by strain rate increase was higher whereas that in the strain capacity was lower. Mesoscale numerical model with randomly distributed polyvinyl alcohol (PVA) fibers was built to analyze relationship between the cross section stress and displacement of specimens with different thicknesses. The results showed that the stress in the cross section and their corresponding relative displacement of block specimen were smaller than those of thin planar specimen under the same loading status. In addition, the cross section stress -displacement relationship of thin planar specimen was more sensitive to the strain rate than that of block specimen, which may be the reason for the weaker strain hardening behavior of thin planar specimens under dynamic tensile loading.