Systems and methods for determining mechanical properties of formation rock using, for example, millimeter-scale test samples of the formation rock are disclosed. The test samples may be single edge notched beam (SENB) test samples. The systems and methods may include performing laboratory testing on the SENB test samples and recording laboratory testing data obtained from the laboratory testing and performing a simulation on a numerical model of the SENB test samples and recording the simulation data obtained from the simulation. The laboratory testing data and the simulation data may be compared, and a determination may be made as to whether a selected degree of correlation is present between the laboratory testing data and the simulation exists. Mechanical properties of the formation rock are obtained from the simulation data when the selected degree of correlation exists between the laboratory testing data and the simulation data.