How can I determine the maximum load on a surface?

[r19ecua]

I'm trying to determine what equations I can use in order to calculate the maximum load (in pounds) across a sheet of plexiglass. Could anyone help me look in the right direction? This is just a sheet that's 10" x 10" x 1/8", that's held by 4 screws. You see, my project involves placing my robotic arm on top of this sheet, but I want to know the maximum weight my arm can carry while on top of this plate! I know (theoretically) that my arm can carry up to 1 pound (approximately). Any direction?

 

[elegysix]

Well, there are a lot of variables here. I would recommend you do load testing to find the maximum weight, rather than trying to calculate it.
The other thing you should watch out for is if your robot lifts something while it sits on your sheet, there will be an impulse that will make it 'weigh' more than it does, briefly, especially if the motion is rigid (not smooth and slow) - that will likely be the time it breaks.