Elastic-plastic fracture toughness of PC/ABS blend based on CTOD and J-integral methods

Abstract

The elastic-plastic fracture toughness of a PC/ABS blend has been investigated simultaneously by the conventional J-integral and the crack tip opening displacement (CTOD) methods for specimen thickness varying from 4 to 15 mm. The critical J (Jc) and the critical CTOD (δc) are based on crack initiation. Another new method to determine Jc based on the close relationship between the J-integral and CTOD has also been developed. Those three critical Jc values, Jc−81, Jc-NEW, and Jc-BS obtained from ASTM E813-81, the new J method, and the equation Jc = mσyδc (1−ν2) of the CTOD method, are comparable and are independent of the specimen thickness. The constraint factor m evaluated from the linear elastic fracture mechanics (LEFM) approach using the Dugdale model is about 1.5. A rotation factor rg of approximately 2 was obtained which is also independent of the specimen thickness. The crack propagation resistance, J-curve (dJ/da) or δ-curve (dδ/da), decreases with increasing specimen thickness. A close relationship between CTOD and J-integral has been demonstrated in this study.