Mode-I fracture toughness measurement of PMMA with the Brazilian disk test

The pure mode-I fracture behavior of polymethyl methacrylate (PMMA) under quasi-static loading was studied using Brazilian disk test. The effects of notch shape and relative notch length on the mode-I fracture toughness measurement were also investigated. The Brazilian disk was loaded using a conventional Shimadzu-5000 testing machine at a constant displacement rate of 0.08 mm/min. The fracture pattern was observed and it was found that under pure mode-I loading, the crack propagates in a direction parallel to the original crack plane. The measured CSIF is found to decrease with increasing relative notch length. The experimental results indicate that the CSIF measured from sharp-notched specimen can be regarded as the fracture toughness of PMMA material. It is also shown that there is no apparent difference on fracture surface morphology between the straight-notched and sharp-notched specimens.