Effect of initial crack length on mode I fracture toughness of PMMA in pseudo compact tension test

Mode I fracture toughness (K-IC) is one of the most important parameters in fracture mechanics and represents the ability of a material containing a pre-existing defect to resist crack propagation. In this paper we investigate the influence of starter notch length on the results of mode I fracture toughness using an isotropic homogeneous material, poly methyl methacrylate (PPMA), of which several disc-shaped specimens were tested using the pseudo-compact tension (pCT) tests. Digital image correlation (DIC) was also employed to assess the distribution and evolution of the strain field during the tests. Very good agreement was found between the K-IC values estimated in this study and those reported in the past for the same material. That indicates that the pCT test method is reliable for the assessment of K-IC. The experimental results also show that the initial length of the starter notch has a noticeable impact on K-IC, although the magnitude of its influence is closely related to material structure and type.