STRENGTH CRITERIA DEVELOPMENT FOR COMPOSITE STRUCTURES BASING ON SOLUTIONS SUPERPOSITION FOR MODELS OF DIFFERENT LEVELS

摘要

The approach to developing strength criteria for composite structures is proposed. It based on superposition of solutions for FE-models of different levels. The first level of FE model is used for analysis of strain state of undamaged composite structure. The parameters of the strain state are considered as base values for estimation of the structure strength taking into account presence of various cracks in matrix.Strength estimation is carried out basing on a database of typical solutions of specific nonlinear task for different areas of the structure. The analysis concerns buckling, post-buckling behaviour of composite skin, nonlinear deformations of matrix under tension, etc. These tasks are solved on the basis of specialized FE models.The combination of the solutions for these traditional and specialized models enables to generate simple and reliable criteria for an estimation of strength of thin-walled structures.Validation of these criteria has been carried out for composite skins with different stacking sequences and with different characteristics of resin on the basis of experimental research of strength. Results of the validation of the strength criteria for orthogonal layers in skin have demonstrated good agreement of numerical results with experimental data.Strength criteria are shown in the paper as examples for different cases of layup and characteristics of fiber and matrix.