|M.Sc Student||Prumanov Leonid|
|Subject||Buckling and Postbuckling Behaviour of Cylindrical Stiffened|
Laminated Composite Plates
|Department||Department of Aerospace Engineering||Supervisor||Professor Haim Abramovich|
|Full Thesis text - in Hebrew|
The aim of the present study is to analytically and numerically investigate the stability of cylindrical stiffened laminated composite plates.
In engineering practice, structures are designed such that the load applied to each compressive member is always much less than its critical buckling load. There are two main ideas that stand behind the study - one of them is to investigate the effect of various parameters - geometric and physical, on the buckling load and on the postbuckling behavior of plates, when nowadays there is a lack of theoretical tools to provide the solution for this type of problems, and the second one is to develop a fast and exact procedure for postbuckling analysis to expand the limit of usage of the composite stiffened plates in air vehicles.
The commercially available finite element code ABAQUS was used to simulate the behavior of the plates. An analysis was performed using a four-nodes shell element S4R which can accommodate laminated materials. Within the present research, a parametric investigation was carried out on more than 1000 different types of the plates.
For plates that the buckling loads can be analytically calculated, a very good correlation between numerical results and analytical solution was found. Then the effect of various parameters on buckling and collapse loads of cylindrical plates was investigated and the results revealed the importance of each parameter. The conclusions, which were drawn in the framework of the present study, might give a good indication to the industry how to design a better stiffened plate to withstand axial compression.
In the last stage of the present research, the postbuckling behavior of composite stringer-stiffened plates was investigated. It is well recognized that these plates can withstand axial loads that exceed their first buckling load. Today, the first buckling load is allowed under operating flight conditions, when the limit load is only 10% above the first buckling load. But these plates can safely carry out larger loads that are not allowed because of a lack of efficient and fast tools to provide the solution for the non-linear postbuckling behavior of plates.
Parallel to the analytical and numerical investigation, an experimental work was carried out at the Aircraft Structures Laboratory at the Technion. The experiments were performed on number of fuselage - representative cylindrical stringer-stiffened panels. The buckling and collapse loads of the panels were in a good correlation to the results predicted by the present numerical investigation, based on the finite element analysis.