Manufacturing defects in composite flanges: modelling and analysis of influence on static strength

This work presents an approximate methodology based on the numerical simulation aimed at assessing how defects affect static strength of polymer composite flanges in load bearing elements used in aeronautical engineering. Various defects may occur in the process of flange forming in the areas of bending, e.g. curvature of the layers, resin pockets, voids, delamination and others. Thus, there is an actual problem of assessing how technological defects affect the strength of this part. The main defects in composite laminates are defined and a review of literature related to strength problems for such structures are presented in this work. The numerical stress-strain analysis of composite flange with main types of defects under force loading condition was carried out with ANSYS software. A two - dimensional axisymmetric finite element model was used. For the development of the structural model a parametric modelling approach was applied, including defect size, configuration and location parameters. The problem was solved in a general statement for an anisotropic elastic body. In order to keep the original part profile, we reduced the overall thickness of the layers in the local area near the defect by the size of the defect, so the overstated value of structural strength was obtained in simulation. The safety factor of the flange was estimated by stress components using the maximum stress criterion. The stresses in the material principal directions and interlaminar shear and normal stresses were determined for analysis. A comparison of the obtained data with the results for a defect-free flange allows estimating the impact of each defect or its combination on the static strength of flange.