A few notes on stormtrooper armor.
The design in my opinion is to imitate the appearance of a skeleton. Following fantasy motifs, Darth Vader is the dark wizard and the stormtroopers are his army of undead. Lucas based much of Star Wars on the old cliffhanger serials and B movies of his day. Imagine the skeleton armies in Sinbad. If you look at the helmet and the plating, the face resembles a death's head and the plating the bones and joints. The Empire is very much based on the Nazis. SS officers would have death's heads on their caps and decorating other parts of their uniforms and equipment.
I played the Star Wars role-playing game and according to the rules stormtrooper armor does supply some protection. Strength is the statistic used to defend against damage. It is measured in a number of dice, the average person being 2D, the hero 3D. Stormtrooper armor provides 1 additional die. A protective vest adds only 1 pip, so by comparison and average of 2D+1 compared to 3D.
Stormtroopers are accurate with rifles in the game, having around a 5D skill rating, again the average untrained person being 2D.
However, in the movies stormtroopers are just an obstacle or foil and pose no great threat for the heros.
Wow. That was a lot of nerd just then.