
Stronger Than Steel: Synthetic Spider Silk [video] - pseudolus
https://www.bloomberg.com/news/videos/2019-08-22/stronger-than-steel-synthetic-spider-silk-is-real-video
======
ggcdn
There are two main objectives when designing conventional structures: strength
and serviceability. We want to make sure structures have sufficient strength
under very rare and severe loading to prevent collapse. But we also want to
make sure they don't move too much under normal loading. It sounds like using
silk would be a challenge to satisfy both objectives in many applications. In
order to actually mobilize the tensile strength, it would require huge strains
that would be incompatible with conventional materials. Or everything would
need to be pretensioned up to some high stress. Likewise, for serviceability
it would require either lots of strand under low stress or pretensioned
strand.

That's not to say these are insurmountable problems, just something Ive never
thought about before.

~~~
dragontamer
The "obvious" solution to using spider silk is to create a weave of it, like a
textile, and then use the spider-silk in the form of a composite.

Imagine spider silk replacing fiberglass threads for example, or carbon-fiber
threads. Its not fiberglass or carbon-fibler per-se that makes the material
strong, its the composite. The mixture of plastic (which provides compressive
strength) with fiber (which provides tensile strength).

There are a ton of composite fibers in the marketplace. I'm not a materials
engineer, so I don't know exactly what people are looking for in their fibers
(aside from high tensile strength). Probably low-weight, high strength... and
probably low-compressive strength (or at least, people ignore the figure).

"Elasticity" in spider-silk sounds interesting, but I'm not sure if thats good
or bad for a composite.

\-----------

The composite for structures is going to be Reinforced concrete: Steel Rebar
provides tensile strength, while Concrete provides compressive strength.

Where spider-silk (or fiberglass / carbon fiber composites) shine, are low-
weight applications. Bicycles, bullet-proof armor, and flywheels. The question
is if spider-silk is actually any better than carbon fiber (or Kevlar)

That's the thing: we have a LOT of manufactured fibers. Maybe spider-silk has
a niche that can be used. But its competing against Carbon Fiber, Fiberglass,
and Kevlar.

\-----------

It seems like Spider-silk has less tensile strength than Carbon Fiber /
Kevlar. However, due to its flexibility, spider-silk can absorb significantly
more energy before breaking (aka "Toughness").

So spider-silk might be superior for stopping bullets in a composite weave,
but it would be awful as a load-bearing structure (unless that load-bearing
structure were expected to be "catching" objects a lot). Hmmm... maybe a
Tennis Racket would be the ideal use of Spider Silk...

~~~
ggcdn
Because I'm a structural engineer, I like to think about the future of
structures, not bicycles. Many good ideas came about by taking something from
one obvious application and transferring it to another. I also don't think we
will be using reinforced concrete in the year 2070 the same way or as
extensively as we are now - the carbon footprint is too large. Maybe these new
materials can spawn completely new types of structural systems that were never
possible with conventional strengths and stiffness. Low weight is ultimately a
goal of structural engineering as well, but not to the same extreme as
sporting goods. Obviously cost comes into play, but many things that were once
prohibitively expensive are now used on structures, including carbon fiber.

Elasticity (or in the case of conventional materials, ductility) is a trait
that has applications in seismic design, so I disagree with your last claim.
The trick is combining the good parts of that material with the good traits of
other materials into a composite that achieves stability under gravity and
predictable deformability under seismic loads.

------
iso1337
The problem with these silk biotech companies will be scale up and competing
with existing cheap and abundant fibers.

Silkworm silk already has issues with water and such clothing has to be
professionally cleaned. Many silks have the property of supercontraction and
will shrink by 50% upon exposure to water.

Furthermore, these silk companies claim they can produce stuff as strong as
natural spider silk, but that’s a very tall hurdle to jump. They stole VC
interest by claiming that the fiber properties are engineerable, but very
little academic research has been done in that space.

So you have to wonder what is the market for expensive fibers that don’t
perform well in the context of clothing that gets wet.

Already you see companies like Bolt Threads pivoting towards cosmetics,
because why not? The technical challenge is much lower and the profit per gram
should be much higher.

------
ianai
Is this strong enough for a space elevator?

~~~
aerophilic
Spider Silk has a tensile strength of 1.3GPa, at a density of 1.3g/cm^3 [0].
This translates to 1300 kg/m3, or a specific strength around 1,000,000.

So short answer is probably “maybe?”, based on the equations here [1], however
there are other mitigating considerations, everything from how would you mass
produce it, to the fact it can constrict up to 50% when wet. Hopefully those
are just engineering problems.

[0]
[https://en.m.wikipedia.org/wiki/Spider_silk#Density](https://en.m.wikipedia.org/wiki/Spider_silk#Density)
[1]
[https://en.m.wikipedia.org/wiki/Space_elevator](https://en.m.wikipedia.org/wiki/Space_elevator)

~~~
abakker
All the synthetic silk products I’ve ever seen are very susceptible to UV
damage. Modern synthetic winch lines are synthetic silks, and while they are
very strong, they need to be kept covered to ensure UV stability.

~~~
ianai
That’s very informative! What do you figure are potentially new applications
for this that aren’t possible without it?

~~~
abakker
Safety. It’s light, and doesn’t store a lot of elastic energy, so when it does
fail it doesn’t whip. That is a feature for winch lines and webbing bits for
climbing.

Usually with these new fibers, the applications are lightness, since for
applications without weight sensitivity steel is pretty awesome.

------
imvetri
Whats the point of using such a good invention for making shoes?

What is the right kind of application for using spider silk?

~~~
gingabriska
It's just a concept shoe made from spider silk. There can be many more
application.

It's biodegradable (I guess) so probably we can use it to replace plastics.

Instead of plastic or metal or wood, we might end up using proteins.

~~~
agumonkey
I can really take stronger biodegradable grocery bags. The corn plastic based
ones are an exercise in softness.

------
sabujp
I think another problem is high heat applications, how well does spider silk
stand up to fire?

------
kontorlaore
So, did they tried weaving a 1-cm diameter rope, and testing it against a
similar diameter steel rope?

