Comparative analysis of the calculation of the stress intensity factor from the results of equilibrium and non-equilibrium tests

Abstract

This article explores the practical use of methods for determining the stress intensity factor at normal separation: eccentric compression of notched cubes and four-point bending of a notched beam. During non-equilibrium tests, the stress intensity factor value was calculated from the value of the breaking load. During equilibrium tests, the stress intensity factor value was determined from the complete equilibrium deformation diagram, taking into account the energy indicators of destruction. The test used nanofiber-reinforced concrete, in which carbon nanotubes are used as crack propagation inhibitors at the level of the cementing agent, and various macro-sized fibers are used at the level of fine-grained concrete. As a result of the tests, it was found that the methods for determining the recovery factor from cubes with a notch and from deformation diagrams showed a good degree of convergence. Fiber reinforcement affects the fracture toughness of a nanocement composite, and high-modulus fiber has a greater effect on fracture toughness than low-modulus fiber. The stress intensity factor is a good indicator for comparing different types of fiber reinforcement in terms of their effect on fracture toughness.