Today's KNOWLEDGE Share :EYRING PLOT

Today's KNOWLEDGE Share

When plotting Yield Stress vs. Log Strain-rate (The EYRING plot, as we call it), one mostly finds a perfect straight line for all polymers.

This line can be created by running at least 3 tensile tests, at 3 different strain rates (a decade apart each, for instance).

Such plot is incredibly interesting as it reveals the strain-rate sensitivity of your polymer (visco-elastic behaviour).

A low sensitivity (green GOOD line) means the Yield Stress remains high at CREEP rates, leading to good creep performance. But it also remains lower at IMPACT rates, making DUCTILE failure more likely.

A high sensitivity (red BAD line) means that Yield Stress will be lower at CREEP rates leading to more creep (bad). But it also means that Yield Stress will be higher at IMPACT rates, making BRITTLE failure more likely.

What I find unbelievably interesting is that this plot tells us that :

"Polymers that are bad in CREEP tend to be also brittle in IMPACT"

" Polymers that have good CREEP performance, also will show more ductile IMPACT performance"

So contrary to the classical anti-correlation between stiffness and toughness, we find here that both creep and impact move together in a good or bad direction when the Eyring slope changes.

So why don't we focus nearly enough on this simple plot ????

It is just a lack of education and scientific knowledge in our industry.

source: Vito leo