Abstract
The J integral method was used to characterize the dependence of stresses and strains in the vicinity of the crack tip in thermoplastic materials with nonlinear deformations. This method makes it possible to establish the correlation between crack growth resistance of the material based on the stable propagation and the crack extension by means of J-R curve, which is an indicator related to the toughness of the material. The paper presents the results of experimental researches carried out on three-point bending test specimens of thermoplastic high density polyethylene - type PE 100, taken from the pipes with 110 mm diameter. Keywords: J-integral, J-R curve, toughness, thermoplastic materials, polyethylene PE 100