Comparative strengths

[Dust Buster]

Kevlar: 2,514 kN.m/kg
Carbon-fibre: 2,457
Glass-fibre: 1,307
Spider silk: 1,069
Steel alloy: 245
Aluminium allow: 222
Oak: 87

I actually had a layer of stab-proof put into the back of my motorcycle jacket, more as a deterrent for road rash. The seamstress was not impressed with the number of broken needles.

What is stab-proof? It is Kevlar coated with a rubbery compound. Kevlar is usually pierced by a bullet. It is the layers of Kevlar weave that traps the bullet (usually) and absorbs a lot of the energy. The rubbery stuff helps prevent that initial piercing.

Why was stab-proof invented? Apparently it came from a request of British parents to protect their children from bullies with knives.

[j-c-c]

I would think a road rash important material attribute would be low heat transfer/resistance, and maybe with an ablative contribution, like maybe nomex?

[Dust Buster]

Kevlar is heat-resistant and used in some fire-fighter uniforms. Natural rubber begins to melt at approximately 180 °C (356 °F).

The point I was trying to make is that Kevlar is stronger, yet one only hears of carbon-fibre manufacturing these days. Carbon-fibre must be cheaper than Kevlar.

[hoodeng]

Graphene is king of the compound materials as far as strength/weight goes, we are still yet to see it in main stream products. but it will be a game changer.

Cheers.

[j-c-c]

Kevlar is heat-resistant and used in some fire-fighter uniforms. Natural rubber begins to melt at approximately 180 °C (356 °F).

The point I was trying to make is that Kevlar is stronger, yet one only hears of carbon-fibre manufacturing these days. Carbon-fibre must be cheaper than Kevlar.

Well nomex is comparatively nearly as strong as Kevlar, and has better heat properties, as I suspect road rash generates a lot of localized heat issues, and i don't see strength being a greater issue. The ablative characteristics of any of these materials is beyond me, which is why I focused on Nomex, regardless, it will mainly come down to the binder used when concerning low temp curing composites as far as thermal properties, not the reinforcement used. CF's main attribute is stiffness, an attribute of reduced importance IMO, for road rash protection..

[Dust Buster]

Both Kevlar and Nomex are aramids. Nomex strands cannot align during filament polymerisation and has less strength. However, it has excellent thermal, chemical, and radiation resistance for a polymer material. When Nomex is worn, Kevlar threads usually hold the fabric together at the seams. When you are sliding along the tarmac and things start getting warm, you want to know that the material has the strength to stay in place (between you and the road).

[pdq67]

Back before I left AP Green Refractories, I had to hot gun industrial furnaces like aluminum reverbs!

We had silvered asbestos coats and pants to try to stop the heat from burning us.

I think they use Kevlar now since asbestos is a no-no!

Oh, hot gunning was done from like 1200 degrees all the way up to 2950 degrees so it wasn't fun at all.

I blistered my cheeks and the backs of my hands doing this crap! I have even stood on ceramic fiber with a 1/2" air hose blowing on me so I could get the hot patch done! Broke up aluminum reverb here!! As well as a cement rotary kiln cooler roof.

pdq67

[lefty o]

nomex is great for resisting heat transfer, but as far as strength, its physical properties are very much like cotton.

[pdq67]

Nomex you say.

Refractory ceramic fiber will withstand upwards to 3,000 degrees!

If I remember right AP Green made 2,000, 2,400, and 2,600 degree fiber at their Pryor, OK fiber plant..

And the stuff looks just like cotton!

pdq67

[Dust Buster]

Some bulletproof vests have ceramic plates.

Many exhaust heat wraps use ceramic fibre that itch like mad and probably aren't good for one's lungs. There's always a layer of sparklies in the engine bay near in situ installs.

[pdq67]

^^^^^^^^^^^^^^^^^
"Many exhaust heat wraps use ceramic fiber that itch like mad and probably aren't good for one's lungs. There's always a layer of sparklies in the engine bay near in situ installs."

Might install the wrap wet???

And I am off the opinion that ALL heat resistant friable fibers are just like asbestos!

Mineral wool, (aka, Block Insulation), slag wool, ceramic fiber, FIBERGLASS, all of them...

I have worked around them all so kinda worry about my lungs.

pdq67

[gruntguru]

https://www.youtube.com/watch?v=o4eNFAJIeHI

[Dust Buster]

I really got a lot out of the longer version: https://youtu.be/KHXVf0SaJpA such as the pros and cons of the different classes: S & E Glass, Kevlar 49 & 29, high-tenacity carbon (which corrodes steel and aluminium; therefore use titanium fasteners)

So, one really needs to know the application (requirement for compression loading (buckling) / tension, stiffness, tensile strength, density / weight, strength to weight, elongation / toughness, flex, abrasion, impact, UV exposure, cost / budget).

[Geoff2]

D/buster, exactly. Application is key. A house brick can withstand a tremendous amount of weight on it when sitting on a flat surface, but will break if you drop it on concrete.

[j-c-c]

I really got a lot out of the longer version: https://youtu.be/KHXVf0SaJpA such as the pros and cons of the different classes: S & E Glass, Kevlar 49 & 29, high-tenacity carbon (which corrodes steel and aluminium; therefore use titanium fasteners)

So, one really needs to know the application (requirement for compression loading (buckling) / tension, stiffness, tensile strength, density / weight, strength to weight, elongation / toughness, flex, abrasion, impact, UV exposure, cost / budget).

OK then share the rational/pertinent details for your decision with the Kevlar road rash protection solution.