Calculations for unknown properties

[alecGraves]

Notes about calculations for unknown properties:

I have been estimating shear modulus with

$G=\frac{E}{2(1 + \nu)}$

where $G$ is shear modulus, E is Young's modulus, and $\nu$ is Poisson's ratio. Young's modulus is usually given.

I generally assume $\nu$ based on the material category (e.g., .35 for nylon-ish plastics), so IDK how correct that is for printed plastics.

Also, tensile strength is usually given, while I usually estimate yield strength to be about 50-90% tensile, depending on the material. If bending strength is given, I might also assume yield strength is close to bending strength (I did this for the PA12-CF material).

For the PA12-CF material, I also used the wet X-Y (strong direction) properties. Thus, it is probably good to have a 50% factor of safety for weak-direction parts. Also, print with a higher temperature to increase layer adhesion and reduce the difference between x-y (strong) and z (weak) directions.