Calibration Coefficients for Residual Stress Measurement in Composite Materials Using Finite Element Method

Problem statement: Since the residual stresses can cause a scienificant reduction in strength of the mechanical components, having a semi-destructive measuring method that would predict and model theses stresses would be an advantage. The hole drilling method has been used, by many researches, for measurement of the residual stresses in different materials. In this article, the finite element method is used to simulate the hole drilling method. Approach: The calibration factors required for measuring the residual stresses in composite materials are performed using a finite element procedure instead of experimental techniques. In this approach, the elements within the whole boundary are firstly removed from the finite element model of the specimen. Then, the average strains released around the whole area are measured using a there-strain gage rosette located near the whole boundary. Results: The calibration factors which are used to convert the released strains to residual stresses are obtained by the hole drilling method. The results for an orthotropic unidirectional ply made of glass/epoxy are presented. Conclusion: The compliance factors are represented as a 3×3 matrix for the orthotropic material. The results obtained from the finite element method are compared with the analytical solution method. A good agreement between the results shows the reliability of the numerical method presented in this study.