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ارائه الگوی تحلیلی برای معادل سازی سازه های مشبک منظم
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ارائه الگوی تحلیلی برای معادل سازی سازه های مشبک منظم

زارعی، محسن Zarei, Mohsen

An Analitical Model for Grid Stiffened Structures of Various Patterns

Zarei, Mohsen | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40599 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Kouchakzadeh, Mohammad Ali
  7. Abstract:
  8. Structural efficiency is a primary concern in today’s aerospace and aircraft industries. This brings about the need for strong and light weight structures. To increase the strength of a panel without considerable increase in its weight, we may use a lattice of stiffeners which may have shells connected to one side of the lattice or both sides of it. These structures are usually called grid stiffened structures. Aircraft fuselage and launch vehicle fuel tanks are some of the many applications of these structures in aerospace and aircraft industries. These structures include two major groups; isogrids (grid stiffened structures with equivalent isotropic properties) and orthogrids (grid stiffened structures with equivalent orthotropic properties). Anisogrids are another group of these structures having more general anisotropic properties. Usually they are not cited in the classification of stiffened structures because analysis of these structures is very complicated and they are rarely used. The ABD matrix (laminate stiffness matrix) defines a relationship between the stress resultants (i.e. loads) applied to a laminate, and the reference surface strains and curvatures (i.e. deformations). In this research, an improved smearing out method is developed to model the ABD matrix of grid stiffened structures. In this method, the lattice of stiffeners is replaced with an equivalent shell with specific material properties. These properties depend on the shape, orientation, size and material properties of the stiffeners. To construct the ABD matrix, we consider a general pattern for the lattice with arbitrary parameters including material properties, size and angle of the stiffeners and rotation angle of the complete grid pattern. Considering this general pattern, we may have different patterns by removing some of the stiffeners or by changing their angles. In addition, the shell connected to the lattice may be of arbitrary material properties or even it may be made of composite laminates. Then 112 Abstract we find the ABD matrixes of the lattice and shell separately, and add them directly to find the ABD matrix of the grid stiffened structure. We use equations of motion for cylinder and elements of ABD matrix, to obtain the critical buckling load for stiffened cylinder with various patterns
  9. Keywords:
  10. Stiffness Matrix ; Grid Stiffened Structures ; ABD Matrix ; Equivalant Material Properties ; Isogrid ; Orthogrid ; Buckling of Stiffened Cylinders

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