טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentManor Amit
SubjectEffect of Tensioning of a Sandwich Plate on its Dynamic
Characteristics in Presence of Discrete Masses
DepartmentDepartment of Aerospace Engineering
Supervisor Professor Emeritus Tanchum Weller
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

In the field of aerospace, structures must be designed with low weight and high load bearing capacity.  This type of structure is more sensitive to dynamic problems associated with its natural frequencies.  In order to increase the structure's natural frequencies there is a need to stiffen the structure.  Usually, stiffening of the structure can be achieved by complicated/expensive or heavy design.

The objective of this study is to examine the possibility to increase the stiffness of sandwich plate structures, almost without increasing their weight or complexity. The structures dealt with in this study are tension stressed 3 layers sandwich plates, where tension is introduced into their skins only.

This way, the natural frequencies will increase and compensate for the decrease of the structure frequencies, particularly the lower ones, which are expected due to discrete mass dispersing on the structure.

This work presents an analysis dealing with the influence of the change in sandwich structures stiffness, by applying tension to their skins, on their dynamic characteristics, as reflected by their natural frequencies.  The analysis was performed using energy methods while considering different discrete mass dispersing on the plates and exposing them to different edge conditions and loads.

The results of the present study show that the natural frequencies are influenced by the magnitude of applied tension that changes the dynamic characteristics of the structure.  This influence is highly perceived when the edge conditions of the structure are of "soft" type. For those edge conditions it is possible to achieve an increase of tens percents in the natural frequencies while applying relatively reasonable tension stresses.