Investigation on the Effect of Different Pre-Cracking Methods on Fracture Toughness of RT-PMMA

Abstract

In this study, eight techniques including coping saw, metal slitting saw, razor blade, cubic boron nitride (CBN) disc, scoring, diecutting and guillotining, diamond disc, and laser cutting methods were used to produce pre-cracked fracture toughness (Kc) test specimens made of poly(methyl methacrylate)/graft-acrylonitrile butadiene styrene blends. The influences of notch shape (radial, rectangular, or angular-shaped and variety of thicknesses), precracking method, chip removing or non-chip removing, and the contact or non-contact methods on the results obtained in fracture toughness tests were investigated. The results were analyzed by two methods, quantitatively and qualitatively, by comparing the obtained Kc results and studying the SEM and optical microscopy images, respectively. The results indicated that the different conditions of a produced pre-crack including; geometry of pre-crack due to geometry of tools, residual stress due to pre-crack creation, heat affected zone, damage of crack tip, and producing crazing around the crack tip could affect the fracture toughness. The maximum difference resulted from different pre-cracking methods was equal to 0.24 MPa.m 0.5 and the lowest value of fracture toughness Kc, 2.53 MPa.m 0.5 , belonged to the scoring method but the highest value, 2.77 MPa.m 0.5 , belonged to the metal slitting saw method. Also, the results indicated that the effects of notching on toughness of RT-PMMA had a low notch sensitivity and the differences between minimum and maximum Kc values was found about 9%.

Carbon Nanoparticles’ Impact on Processability and Physical Properties of Epoxy Resins—A Comprehensive Study Covering Rheological, Electrical, Thermo-Mechanical, and Fracture Properties (Mode I and II)

“…The effect of different notching techniques for glassy polymeric SENB samples have been intensively investigated in literature [35,36,37,38]. They all conclude that an infinitesimal sharp notch leads to a homogeneous stress field and no prior plastic deformations in front of the crack tip.…”

Mixed-mode fracture prediction of acrylonitrile butadiene styrene material fabricated via fused deposition modeling

“…The sharp crack in fracture test specimens can be created using many approaches such as coping saw, scoring, laser cutting, fatigue pre-cracking. 26 For specific case of polymers and plastics, 27 the use of a razor blade for introducing sharp cracks is a common practice due to the small crack tip radius and smaller residual stresses around crack tip vicinity after pre-cracking. 28 Three-point bending tests were performed on the printed specimens using the same testing device (Figure 3).…”

Influence of Precracking Techniques on Fracture Toughness of Carbon-Carbon Composites

“…Such methods include pressing a sharp razor blade into the notch, use of a blade on a milling machine, use of a coping saw or hacksaw, use of a CBN disc, use of a scoring knife, use of a diamond disc, laser cutting, etc. [15]-[17].…”