Methods of Pre-Cracking and Investigation of Effects on Fracture Toughness of Poly(methyl methacrylate)

In the present research, pre-cracking methods and effects of pre-cracking on the fracture toughness of poly(methyl methacrylate) have been investigated. Pre-cracking methods including razor-sawing, razor-gently pressing, razor-tapping, and razor-slotting were used to produce pre-cracked for studying of fracture toughness (Kc) test specimens made of poly(methyl methacrylate). The obtained fracture toughness Kc values showed that in addition to the geometry of crack tip, the Kc strongly depended on crack tip sharpness. Moreover, the damage in front of crack and residual stress could be effective on the fracture toughness of samples. The maximum difference resulted from different pre-cracking methods was equal to 0.16 MPa.m0.5 and the lowest value of fracture toughness Kc, 2.49 MPa.m0.5, belonged to the razor-slotting method but the highest value, 2.65 MPa.m0.5, belonged to the razor-sawing method.