PhD, University of Cincinnati, 2000, Engineering : Aerospace Engineering

The ultimate goal of the present research is to come up with an accurate and efficient analysis approach for composite and sandwich shells, which is simple enough to be capable of implementing into a FE code without significantly affecting its computational efficiency, and at the same time gives good accuracy in predicting the behavior of layered shells. It has to be capable of accurately modeling both overall behavior, and the local distribution of strains and stresses in all layers and all constituents in the composite laminae. Two different approaches are utilized in the attempt to fulfill the final research objective of the present work. First, a homogenization procedure for the FE analysis of sandwich shells is developed. The procedure works on the material constitutive level. A homogenization of the sandwich shell is performed at each call of the corresponding constitutive subroutine. Thus the sandwich nature of the problem is hidden from the main FE program. As a consequence there is no need to develop a new shell element formulation, but instead the available homogeneous shell elements in the utilized FE code can be used for the analysis of sandwich shells. However, the defined homogenization procedure works with first order shear deformable shell elements, which sets a limit to the accuracy with which the transverse distribution of the unknowns is represented. To overcome this, a higher order shear deformable shell element is formulated and implemented into a general nonlinear explicit FE code. Using the differential equilibrium equations and the interlayer requirements, special treatment is developed for the transverse shear, resulting in a continuous, piecewise quartic distribution of the transverse shear stresses through the shell thickness. A similar approach is applied to the transverse normal stresses, which are represented by a continuous piecewise cubic function. The FE implementation is cast into a 4-noded quadrilateral shell element with 9 degrees (open full item for complete abstract)

Committee: ALA TABIEI (Advisor) Subjects: Engineering, Aerospace