Tires: tires, steel belts, stress concentration

Question
Could a person repair a flat by installing an inner tube in the tire?

Answer
Rocky,

No, tubes should not be used in place of a proper repair.  

The repairable area of a tire is the tread excluding the outermost rib.  The repair can be no larger than 1/4" and must consist of a plug AND a patch.

The tread has 2 steel belts which stiffens the area, making the movement of the tread area fairly small.  This helps the adhesion of the patch.  The patch is there to make the tire air tight, although it has a bit of a "bridging" effect for the structural elements.  The plug is there to prevent outside contaminants form enter the injured area (Water tends to rust steel belts.)

The outermost rib is excluded because that's where the edges of the belts are.  The belt are the most highly stressed area of the tire.  Damage to that area tends to cause the belt to separate - which sometimes has tragic consequences.

The sidewall undergoes a complex motion as the tire rolls.  So complex that patches do not adhere well.  The other reason this area is not repairable is that the motion of the sidewall tends to cause cracks to radiate from the injured area.  This takes some time to develop, but when the sidewall fails, if will do so suddenly and you lose the traction that corner of the vehicle had and the car could go out of control.

If you want to know more about crack propagation, look that phrase up in Wikipedia.  Also, stress concentration is a related subject.