Size effects on fracture toughness of quasi-brittle materials – A new approach

A new approach called the modified maximum tangential stress criterion has been developed for investigating size effects on mode I fracture toughness of quasi-brittle materials. This approach employs the maximum tangential stress criterion while accounting for the higher order term of Williams expansion A3. Having assumed that the FPZ length changes with the specimen size, a formulation was suggested for expressing the variation of FPZ length versus the specimen size. Some experimental results reported for concrete and limestone were employed to assess the proposed criterion. It is shown that the proposed approach provides good estimates for the experimental data.