Ultra high stretch cycle elastics?

[electrical_eng]

Hi all. I'm trying to find a durable elastic material for a project of mine but I can't seem to find the needed information. basically what I need is a elastic/rubber band that can withstand at least 100 000 (or preferably over 1 million) stretch cycles without its resting length increasing more than a few percent.

In my device I have a rubber band that is 100mm long that gets stretched to 170mm in each cycle and if its resting length increases more than 2.5mm then the device will cease to function. I'm aiming for at least 100 000 stretch cycles and a temperature range between -15 and +35 celsius with the resting length staying inside -2.5 and +2.5mm.

Are there any materials that can handle this?

Thanks!

 

[Danger]

Have you investigated Silastic? I'm not sure how far it can stretch, but it sure is durable. Its temperature range far exceeds your requirements, and it's chemically inert (in any normal circumstance).

 

[lostminty]

Could a spring be more appropriate?

 

[electrical_eng]

@Danger

That looks promising. I will try it and see how it works, thank you.

@lostminty

Do you know any specific types of springs that are known to withstand a very high number of stretch cycles?

 

[lostminty]

Do you know any specific types of springs that are known to withstand a very high number of stretch cycles?

The process of failure is fatigue. In turn fatigue also has a temperature dependent process called creep. You'd have to select a material that can withstand the cycles at the specified max temperature.

Having said that, many steels possesses a fatigue limit, which is loosely defined as a cyclic load that it will never (statistically speaking) fail under. As long as the cyclic load is well below the fatigue limit, and the temperature isn't in the region of creep occurring then any will do.

Spring steel should be fine.

 

[lostminty]

To add,

You will have to analyse the force the spring will be under, then convert it to a force/area to get the tension. This can be compared to the fatigue limit of spring steel to see if its under. If it isn't then one will have to choose a spring with a larger diameter wire.

 

[manifespo]

resilin

The super elastic protein in insect wings and legs... resilin

Resilin or elastin

 

[Danger]

The super elastic protein in insect wings and legs... resilin

Resilin or elastin

That stuff is bloody amazing. I looked at only the Wikipedia link, because I'm very tired right now. While it has been synthesized through genetic manipulation, and is intended to be used in tennis shoes, I didn't see an explanation of how it is maintained outside of a host body or artificial version thereof. What keeps it alive?

 

[mheslep]

The super elastic protein in insect wings and legs... resilin

Resilin or elastin

I don't know about this particular case, but the ability of many biological materials that perform superlatively over the long term even under harsh conditions, compared to inanimate materials, is often due to in part to regeneration over time. Chloroplasts in plants come to mind, being regularly destroyed by sunlight.

Thus if the design approach is to "do it like nature does it" then the first step may have to be, "grow the material in Petri dish and keep it alive"

 

[manifespo]

http://scholar.lib.vt.edu/theses/available/etd-06212010-163917/unrestricted/King_RJ_T_2010.pdf

a quote from this linked pdf about the mechanical properties of resilin

"Resilin is an almost perfect elastic protein found in many insects. It can be
stretched up to 300% of its resting length...While much is known about the static mechanical properties of resilin, it is most often used dynamically by insects. Unfortunately, the
dynamic mechanical properties of resilin over the biologically relevant frequency range are
unknown."

in other words, science doesn't understand the fluid mechanics of resilin yet... i can imagine there will be future combinations of graphene, nanotubes, buckyballs and resilin-esque UV-proofed biopolymers

although they might not be the best or most viable material solutions to this post, i do believe they fit the subject of the original post - "ultra high stretch cycle elastics."

recombinant elastin and resilin have been produced as well as other biomimetic hyper-elastomeric biopolymers
"Design and production of a chimeric resilin-, elastin-, and collagen-like engineered polypeptide."

 

[manifespo]

http://phys.org/news/2013-07-insect-inspired-super-rubber-medicine.html