User:Eas4200c.f08.gator.edwards/Textbook Chapter One

There are two basic aircraft design goals: we want the aircraft to be both light and strong.

The desired aircraft material properties include: high stiffness, high strength, and lightweight.

Stiffness is the Young's Modulus  $$\displaystyle E$$ (slope) in linear relation between stress  $$\displaystyle \sigma$$ and strain  $$\displaystyle \epsilon$$, i.e.,   $$\displaystyle \sigma$$ =  $$\displaystyle E$$  $$\displaystyle \epsilon$$

Strength includes yield stess  $$\displaystyle \sigma$$ Y, and ultimate stress (rupture stress)  $$\displaystyle \sigma$$ u.

Toughness is the material's ability to resist fracture and damage. This is also called fracture toughness.

Some high stiffness and high strength materials include: steel alloys, titanium alloys (which have lower stiffness and strength than steel alloys), and aluminum alloys (which have lower stiffness and strength than titanium alloys).

A high stiffness and low toughness material is glass.

Some low stiffness and high toughness materials include: plastic and nylon. An example of a meterial with good fracture toughness is aluminum (which has lower stiffness, strength, and fracture toughness than steel alloys) and it is used in aircraft skin.

Some high stiffness and high toughness materials include: composite materials.
 * composite materials- fiber reinforced composites where the material used as the base material (called the matrix) is reinforced with many fibers (which increases strength and stiffness).

...FILL IN MORE INFO HERE