The nonlinear relationship between local and macroscopic parameters of dynamic fracture in brittle composite materials

Abstract

Abstract The paper describes results of a numerical study of the influence of composite structure parameters on the strength and fracture time of brittle materials under dynamic loading. The study is carried out on model concrete samples with different volume fractions of reinforcing inclusions and micropores. Simulation results show that the conventional principle of proportionality of the change in the incubation time of the fracture to the change in the linear dimensions of the fracture region is not applicable when a change in the spatial scale of the region is accompanied by a qualitative change in the parameters of the composite structure. The key factor determining the nonlinear nature of the change in the fracture incubation time during the transition from macroscale to lower scale representative volumes is the factor of phase interfaces, on which primary damage is predominantly localized. This conclusion is confirmed by much more pronounced dependence of the fracture time and dynamic strength of concrete samples on the quantitative concentration of inclusions (i.e. the characteristic distance between zirconia aggregates or micropores) than on volume fraction of inclusions.