When to use flexural modulus
When to use flexural modulus
(OP)
I've been recently looking at switching over from a metal to a plastic for one of my components. The plastic supplier has provided values for tensile (Young's) modulus and flexural modulus. I'm doing some hand calculations to predict deflection of a circular beam under a simply supported 3-point bend scenario and my default is to use Young's modulus.
My question is when is flexural modulus used in stress and strain calculations for elastic beams? Or is flexural modulus only used to compare different materials? I'm guessing the later given my understanding of the test methods such as ASTM D790.
My question is when is flexural modulus used in stress and strain calculations for elastic beams? Or is flexural modulus only used to compare different materials? I'm guessing the later given my understanding of the test methods such as ASTM D790.





RE: When to use flexural modulus
I would use tensile modulus if my part will be stretched.
I'd use compression modulus if the part will be compressed.
I am not being flippant. Use the property that fits how the part will be used.
Deflection of a circular beam under load = flexural modulus
If you have only one and need the other tensile and flex usually work out close to one another. There are exceptions.
Chris DeArmitt PhD FRSC CChem
RE: When to use flexural modulus
RE: When to use flexural modulus
If going from metal to plastics, redesign is usually necesary to account for their lower stiffness but higher formability.
RE: When to use flexural modulus
Chris DeArmitt PhD FRSC CChem
RE: When to use flexural modulus
Flexural Modulus per ISO 178 = 21.2 GPa
Tensile Modulus per ISO 527 = 15.0 / 9.9 (parallel / perpendicular to fill direction)
Compression Modulus per ISO 604 = 11.1 / 9.7 GPa (parallel / perpendicular to fill direction)
Shear Modulus per ISO 15310 = 3.6 GPa
The flexural modulus can be about twice that of the tensile or compressive modulus!