I've plans for somewhat 'realistic' (and that's already quite a stretch of the word) superhuman characters whose muscles have the strength, density, and tensile strength that can stop most low-powered firearms (probably a 9mm pistol at the most). I figured that strength and density doesn't play a huge role with stopping bullets, but do offer some defense against stabs and slashes (and the super strength thing). An object's tensile strength is usually what stops bullets, but a muscle's tensile strength is usually quite low (no matter how much you weightlift), so I was wondering if having bullet-stopping tensile strength on one's muscles would drastically change a character's physical characteristics? Specifically, would it change what they look like? Would they still even look human?
My friend, grab graphene and roll it. Voilá! nano tubes.
These are posed as real world wonders that can make almost anything (except leaving the lab so far.... )
The mechanical upper limits are dictated by the weakest part of the chain. In this case, since the material that makes the muscle can take TONNES per strand of hair, your ligaments will snap.
Say your ligaments are anchored to the bone using nano tech too.....Your bones snap. So you add a graphene matrix in your bones. Now you can take a hit.
Lets distribute that energy even further.
Add non newtonian layers that hardens on violent impact like suspended silica or calcium on some liquid. Liquid armor on the wiki
The end result? Get shot, your skin outer layer gets damaged but as soon as it hits the subdermal muscle tissue, it inflicts pressure. The pressure makes the suspended particles push the strata out and harden. Since this is contained on a material taht can hold tonnnnnes of kilograms in tension, won't burst.
Possible cons would be how to get a surgeon to operate you in the event you have a medical issue. Run of the mill tools won't cut it.
Also you take all the energy since even a 50 cal won't pass! A full auto machinegun will push you, since it will transfer almost all the energy to you.
A 50 cal could hurt your brain due to clashing inside your skull. Most common injury on traffic is when your organs hit your ribcage or brain hits the inner skull.
Instantly accelerating as effect to .50 MBG to the triceps will mess your internal organs something fierce.
9Mil parabellum will be a risk on your head since your eyes lack protection. Also your fingers lack any real muscle group to shield them.
All in all, a real dangerous individual who can take thousand of Nato 7.62 and lower bullets to the gut/arms/legs. And stands a fair chance to take a 50 cal and tell the tale. Not to shabby, eh?
There are 3 general ways to make something more bulletproof:
1. You can make it harder so that it can disintegrate the bullet on impact
Your muscles' ability to give and flex is vital to motility. Making them hard enough to disintegrate a slug would make them useless as muscles; so, I highly recommend avoiding this approach.
2. You can make it thicker so that the bullet needs to ablate more material to penetrate it
Thicker muscles would make you slightly more bullet resistant. A low calibre round that has to go through thicker pectoral muscles is less likely to make it past your rib cage to hit a vital organ, but muscles would have to be obsenely thick to actually stop anything bigger than a .22. Again, you run into the issue of mobility vs protection. As many bodybuilders can tell you, by the time your muscles get that thick, you lose most of your flexibility.
3. You can make it better at impact distribution.
This leaves impact distribution. Your muscles are already great shock absorbers. It is why a person with good muscle tone can take a punch to the gut so much better than someone who is out of shape, but muscles have a weakness when it comes to being penetrated by bullets. They are striated.
This means they are made out of parallel fibers optimizing their ability to pull along their needed vector. Along that angle you can punish them all you want with relatively little risk of injury. However, bullets generally hit muscles along the sides which allow them to force themselves between the muscle fibers with relatively little force. If muscles were woven more like kevlar, they would be immensely harder to penetrate. Unlike thicker or harder muscles, woven muscles would not significantly reduce flexibility, but you might suffer a bit of a reduction in pulling strength since you are no longer pulling straight.
Perhaps a better option for natural armor without seeming less human would be reinforcing your person's entire body with dura mater.
Dura mater is the outermost protective membrane that covers your brain and spine. It is exceptionally strong, flexible, and made out of irregular cross-woven fibers. A report from the New Jersey Public Health System shows that the dura mater of rats can withstand 1.3 million Pascals of stress, which is a lot especially given their size. By layering dura mater between your skin and striated muscles, your person would look, feel, and move very much like a normal person, but when shot by a low caliber round, the fibers of the dura mater would distribute the impact across a large cross section of muscles instead of letting it just pierce between them. With the impact distributed, your muscles could do what they do well and compress.
By distributing the impact across a larger surface, you'd probably have torn skin, plenty of bruising, and some some serious muscle inflammation after getting shot, but the bullet be a lot less likely to be able to impact in major organs.