|M.Sc Thesis||Department of Aerospace Engineering|
|Supervisor:||Assoc. Prof. Abramovich Haim|
|Full Thesis text|
The present study deals with the "dynamic buckling" of a laminated composite stringer-stiffened curved panel. The "dynamic buckling", in the present study, is concerned with the unbounded lateral response of the panel, which is subjected to an axial impact load.
In panels stiffened by relatively widely spaced adequately stiff stringer stiffeners, the structure may pass through two major states before its total collapse: buckling of the panel skin between stiffeners and buckling of the stiffeners themselves. This study focuses on the lowest buckling load of the stringer-stiffened panel, which is, buckling of the panel skin between stiffeners.
The analysis of the laminated composite stringer-stiffened cylindrical panel was performed by using the commercial ANSYS finite element software.
In the present study, the equation of motion approach was applied. By this approach, the equations of motion were numerically solved for various load parameter values (loading amplitude and loading duration) to obtain the system response. Special attention was given to the neighborhood of loading durations corresponding to the period of the lowest bending frequency of the skin. Two different methods were used to define the dynamic buckling load. The first one was based on the Hutchinson-Budiansky dynamic buckling criterion. According to this criterion, dynamic instability occurs when a very small increment in the applied load results in a relatively large increase in the response of the structure. The second one suggests that buckling of the panel skin between the stiffeners is similar to buckling behavior of flat plates. Consequently, the buckling load of the plate, which is in our case the lowest dynamic buckling load of the panel between the stringers, was determined as the first meeting point of two tangents drawn on the load-displacement curve of the plate (a similar method employed to experimentally determine the buckling load of a plate).
The results of determining the dynamic buckling load of the panel skin according to the Hutchinson-Budiansky dynamic buckling criterion showed that for all of the loading durations that have been checked, "dynamic buckling" loads were higher than the corresponding static buckling load. Unlike those observations, recognizing of the dynamic buckling load of the panel skin by the second method (the first meeting point of two tangents on the load displacement curve of a plate) showed that for all of the loading durations that have been checked, "dynamic buckling" loads were lower than the corresponding static ones.