Study On The Application Of Composite Materials To Marine Hatch Cover And Its Multi-scale Structures

Recently, the design and fabrication technology of marine hatch covers has beencontinuously improved. New techniques and devices have been widely used in manufacturingmarine hatch covers. Steel is a common material for hatch cover because of its superiormechanical properties and low price. However, traditional steel-made hatch covers have cleardisadvantages, including too heavy, poor corrosion resistance, and high routine maintenancecosts. On the contrast, as an alternative of steel material, the composite hatch cover offerslighter weight, better corrosion resistance and designable, which provide a great potential forusing in marine industry.The application of composite materials in large and medium-sized marine hatch covers isproposed in this thesis, and analysis of structural and mechanical properties of the compositehatch cover is conducted from meso-to macro-scale. Macroscopically, the compositematerials are considered to be anisotropic homogeneous. In macro-scale analysis, a typicalsteel-made hatch cover is firstly selected; then the mechanical characteristics are obtainedthrough structural analysis. Based on the computed data, the material components andlaminate layer schemes are determined, and finally, the structural analysis is carried out on thecomposite hatch cover. In this thesis, different composite materials and layer schemes of thehatch covers are also analyzed. In addition, the manufacturing costs for both steel andcomposite hatch covers are evaluated and analyzed. The potential of the composite hatchcovers for using in marine structures is well proved, from the fabrication cost of view.Mesoscopically, composite materials are considered to be heterogeneous. Based on theprinciple of strain energy equivalence and the failure criteria of the matrix and fiber, thestiffness and strength of the unidirectional and woven composite are studied. Firstly, athree-dimensional finite representative volume element (RVE) model of the compositematerials is established. Secondly, material properties are assigned to the fiber and matrix,and the periodic boundary conditions are imposed on the RVE. Thirdly, macro mechanicalproperties of the RVE are gotten by analyzing the relationship between stress and strain,which obtained from the RVE analysis. In addition, by increasing the boundary displacementof the RVE and applying the component material failure criteria, the strength of the RVEmaterial can be obtained by integrating over the loading surface of the RVE when thecomposite component material starts to fail. By comparing the experimental and theoreticalresults, it is shown that the simulation results computed by the meso-mechanics finite element method are in good agreement with the measured data. All analysis methodologies andconclusions developed in this study will be useful to guide the design and optimization of thecomposite marine hatch cover.