محمدرضا ماهینی

Composite tubes are being vastly used in the oil, gas, and water industries for transferring underground fluids and highly corrosive liquids. Glass Resin Epoxy (GRE) pipes are adopted as a more economically sound alternative compared to steel tubes due to their lower corrosion and higher strength, hardness, and fatigue resistance. The widespread use of GRE tubes, has encouraged researchers to conduct empirical and theoretical researches towards a better understanding of the mechanical properties, failure, and response of such tubes in diverse loading circumstances. Some GRE pipe material properties, such elasticity moduli, Poisson’s ratio, and tensile strength are simply and accurately determined by the aid of the standard tensile test. On the other hand, the reliability of the GRE pipe compression properties derived from compression tests performed on very tiny speciments, is a matter of serious concern due to the locality and buckling errors. However, extensive compressions are expected during the service life of burried pipes. In this thesis, the GRE material properties in compression are explored by introducing the ASTM D2412 flexural stiffness test force-displacement results to an inverse analysis approach. To this end, the flexural stiffness test setup for an 8-layer, 2.5mm thick GRE pipe with a diameter of 200mm and diverse filament winding angles of 45°, 55°, and 65°, has been numerically simulated in ABAQUS. The Hashin material model has been attributed to the pipe material and by defining a proper discrepancy function, a set of sensitivity analyzes has been performed to assess adequate sensitivity of the test measurable quantities to the sought parameters. The discrepancy function has been minimized through an interaction constructed between Mathlab, Phython, and ABAQUS environments, and in order to verify the proposed method, an analytic response relevant to a priori known set of material parameters, has fed to the constructed algorithm as pseudo-experime