Flexural behavior of porous isotropic ice under three-point bending tests

Understanding ice flexural behavior is essential for assessing interactions with structures in cold environments. The mechanical response of ice depends on microstructural properties, such as grain size and porosity, which vary widely in natural ice. Existing bending test data often lack detailed microstructural characterization, making it difficult to interpret or generalize the results. In brittle materials such as concrete or rock, pores commonly act as failure-initiating defects. Therefore, porosity (pore size, shape and density) should be considered a key parameter when studying ice fracture. Here, we provide a robust set of bending experiments on well-controlled isotropic polycrystalline ice microstructures and investigate the role of porosity in ice failure. Two porosity levels were studied, characterized at high resolution by micro-computed X-ray tomography. Analyzing the bending failure by means of the Weibull model reveals that the sample failure is initiated by different defect populations, in relation to the porosity. Providing that the Griffith/Irwin failure criterion can be applied, the measured pore distribution allows the prediction of a critical stress for defect activation. Compared with measured failure stress, this prediction enables discriminating the defect population responsible for failure and offers a mechanistic interpretation of the volume effect observed in porous ice flexural strength.