Boundary Element Simulation of Size Effect for Quasi-Brittle Materials by Using One-Size Specimen

A multizone nonlinear boundary element method is used to simulate the size effect of quasi-brittle materials that are modeled as randomly dispersed particulate composites with randomly distributed microcracks located between the particles and matrix. Usually a series of geometrically similar specimens are used to describe the size effect of materials. In this paper, a one-size specimen method for determining the fracture energy Gf and effective process zone length cf is proposed and verified by numerical simulation. The specimen used for boundary element simulation is confined to only one shape and one size but with different initial crack lengths. A three-point-bend beam and a compact tension specimen are used to expand the range of brittleness number and therefore increase the degree of confidence of the results. Notchless specimens of the same size are also calculated and used to supplement the data of one-size notched specimens. The shape, size, and location of the fracture process zone caused by development of microcracking are observed. The results of Gf and cf obtained from the one-size specimen method are compared with a commonly used method and a good agreement is shown.