Fracture Properties Analysis of Steel Fiber Reinforced Concrete Using Digital Image Correlation

Resumo

This paper proposes a strategy to obtain fracture properties of steel fiber reinforced concrete (SFRC)
based on the application of the digital image correlation method (DIC), where the data is taken from a three-point
bending test (3PBT). The great demand for mechanical tests in engineering induces the usage and development of
several alternative measurement methods. In this context, DIC is a practical, accurate and inexpensive technique
for measuring surface displacement in a non-intrusive way. DIC consists in correlating pairs of images taken from
the surface of the specimen under stress in distinct stages of load, resulting in the displacement fields. By using
the concepts from linear elastic fracture mechanics (LEFM), the displacement fields can be applied to evaluate
some fracture properties of the material. The strategy explored in this work uses images taken from a 3PBT of a
SFRC specimen as input data and measures the displacement field by DIC using the open-source software NCorr.
This displacement field is used to create virtual extensometers in order to study the crack opening. The fracture
properties are then computed from LEFM equations with the displacement previously calculated. The results show
a clear effect of the fibers on improving the support on Mode I cracks. It also indicates a smaller gap in the
material’s response between the transition phases of the double-K parameter analysis. The proposed strategy is
a simple and inexpensive alternative, and it can be a powerful mechanism to analyze and validate the materials
properties used in several engineering problems.