عنوان مقاله [English]
Â A . Fereidoon1,*, F . Yektaye Kia2 Â Â Â 1- Associate Professor, Faculty of Mechanical Engineering, Semnan University, Semnan, Iran. Â 2- M.Sc. Student, Faculty of Mechanical Engineering, Semnan university, Semnan, Iran. Â * Corresponding Author: firstname.lastname@example.org Â Â Abstract Â In this paper, the J integral method is used to calculate and analyze the crack of laminate composite materials .In this study, crack under different angles in different layer will be investigated and the critical state is determined. The analysis of crack will be done at first by a finite element software and then a separate program for integral J on finite element software is calculated numerically. By using the calculated J, the stress concentration coefficient was calculated . The error is considerable when we utilize software for calculating stress concentration directly because of the existence of singularly at the tip of crack. By changing the path of integration of J . t the stress concentration obtained are more admissible.