Quoted from Zzap:Here's a few of the parameters of eSun PLA+ to give you an idea of how the properties of 3d filament can be measured.
Density(g/cm3) 1.23
Heat Distortion Temp(℃,0.45MPa) 53
Melt Flow Index(g/10min) 5(190℃/2.16kg)
Tensile Strength(MPa) 63
Elongation at Break(%) 20
Flexural Strength(MPa) 74
Flexural Modulus(MPa) 1973
IZOD Impact Strength(kJ/㎡) 9
Those are great starting points to understand the material and are needed if you are going to try to do a finite element analysis of your model. If you are looking for values in lb/in^2 (psi) , 1 mega pascal (MPa) is roughly 145 psi.
Your part is also going to be greatly influenced by the geometry, such as if you are creating stress concentrations that will create failure points. What are the loading conditions of the part? Is it under tension, compression, is there a torque or bending moment being applied? Will the part move? How is it supported? These are all important in determining how strong your part is and weather it will fail.
How your print is printed, such as line height, nozzle temp and size, in fill pattern and percentage of fill, etc will have an impact on the final part strength.
If you want to know more about material properties and how they are tested, Wikipedia has some good entries that cover some of what you would learn in a 100 level strength of materials class in engineering school.
https://en.wikipedia.org/wiki/Ultimate_tensile_strength
https://en.wikipedia.org/wiki/Flexural_strength
https://en.wikipedia.org/wiki/Izod_impact_strength_test