טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentFernandes Elnatan
SubjectThermoelastic Deformations of Laminated Composite Structural
Elements
DepartmentDepartment of Aerospace Engineering
Supervisors Professor Haim Abramovich
Professor Emeritus Ori Ishai (Deceased)
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

Orthotropic composite materials have many advantages comparing to isotropic materials. One of the advantages is the ability to design the Coefficient Thermal Expansion (CTE). This advantage has a significant impact on aerospace structures design., the goal of this research is to demonstrate as to whether an approximation of CTE of a cylindrical composite shell structure can be obtained by analyzing a flat composite of the same material configuration.A detailed literature review was performed on the composite components properties in order to define the appropriate material for the research. Finally, a flat laminate made of AS4/3502-2 (Hexcel) was defined for analytical and experimental investigation. The first part of this research deals with the planar problem. Therefore, a plate was defined with its CTE to be as close to zero as possible on the x-axis. In contradiction the y-axis direction was design to be as big as possible in order to obtain experimental measurements using the available equipment for the research. In order to achieve the above plate properties, a parametric analysis was performed applying the Classical Laminate Theory (CLT). Plied orientation within the plate was chosen to be the main parameter to examine. The analysis result after taking into account basic rules of CLT was the following laminate [02, + 452, 02, - 452, 0] Sym. As already mentioned, the theoretical results were practically tested and validated by experiments. In the experiment Thermal strains were measures under quasistatic thermal load. The impact of moisture effect on strains was investigated as well and it was found that this impact could be neglect able comparing the strains caused by the thermal load. The second part of the research deals with the three-dimensional CTE analysis and comparison to the planar results. FEA was performed on a cylindrical shell model defined with the same material as the planar laminate. It was found that CTE vs. orientation of strains behave like in the planar case. However, The result difference increase as far as the angle is closer to the radial direction. It may be assumed, that the reason for that is the impact of curvature. Therefore, It can be concluded that Planar CTE analysis can be applied for preliminary design of a cylindrical shell on the axial direction. In addition it is most advised to validate the results by practical experiments as well as Theoretical analysis.