User:Eas4200c.f08.gator.edwards/Class Notes

Structural Elements
Aircraft are assembled from various elements that are made to withstand different loading conditions (axial, bending torsion).

Basic elements include:
 * axial members:truss/bar element
 * shear panels
 * bending members: beam
 * torsion member: bar/beam torsion

Some of these structural members have been introduced in statics and mechanics of materials.

Stringers


Q: Should bars with rectangular cross-sections be used for stringers?

A: No, bars with open thin-walled cross-sections should be used. This is because they are easier to manufacture (stamping of thin, flat sheets of metal) and they are easier to install on the aircraft (by rivetting. They also are light and strong and we want stringers to resist bending imposed from external pressure as stringers are reinforcement elements. By looking at the figure, we can see they both have the same Iy.

Q: Why don't we use vertical walls on a stringer (designated by the dotted lines in the figure)?

A: There can be many reasons as to why, with one of them being the ability to stockpile stringers when the arms are bent slightly outward. There can


 * also be strucutral reasons for this.

Shear Panel


Shear panels are thin sheets of material that can withstand in-plane shear loads.

$$G$$ = shear modulus

$$\gamma$$ = shear strain - counterpart of $$\epsilon$$, describes change in right angle between two (fictional) lines in the material; due to deformation

$$u=u_{x} ,\quad v=u_{y}$$, \quadby definition

$$\gamma = \frac{\delta u}{\delta y}+\frac{\delta v}{\delta x}=\frac{\delta u_{x}}{\delta y}+\frac{\delta u_{y}}{\delta x}$$

$$u$$ = displacement along x-direction

$$v$$ = displacement along y-direction

$$\varepsilon_{xy}$$ = tensorial shear strain = $$\frac{1}{2}\gamma _{xy}$$

Inspirational Quotes
 About independent thinking :

From The Beatles' "Think for Yourself":

"Think for yourself

'cause I won't be there with you"



 About intelligence :

From Montesquieu:

"Intelligence is the ability to see the difference between similar things and the similarity between different things."