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Stressed Explosive

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Defect-free crystals can endure tensile strains which are just below those needed to break all the interatomic bonds in the material. (Most materials have defects which act as stress concentrators, meaning the material will break well below this level of strain.) As a result, when such crystals break in tension, they often disintegrate into microscopic particles, since the stored strain energy was almost enough to break every [longitudinal] bond in the crystal.

As a result of this, the strain energy in a highly-strained crystal can be roughly equivalent to its chemical energy.

It follows, then, that a highly-strained crystal of an explosive will release significantly more energy when detonated than an unstrained crystal. In other words, its explosive yield will be significantly (maybe 10-30% higher) if it is pre-stressed.

(As an aside, many explosives are already stressed at the molecular level, since they contain rings of atoms that can't adopt their preferred bond angles.)

How, though, to make pre-stressed explosives that can be easily handled? Well, one way would be to make long-chain polymeric explosives and encapsulate them in very fine glass capillaries. In fact, the ideal would be to have an explosive that can survive glass-melting temperatures (which can be quite low, with the right sort of glass), and to draw out fibres consisting of a thin glass skin with an explosive core. If the explosive polymer melts at a different temperature to the glass, then a lot of strain will be built into it as the fibre cools, due to differential contraction of the glass and the explosive. Once cooled, the fibres could be compacted, woven or otherwise formed into suitable shapes.

MaxwellBuchanan, Feb 26 2019

Octanitrocubane https://en.wikipedi...iki/Octanitrocubane
Should be #3, but not yet made to pack densely enough [notexactly, Feb 26 2019]

Heptanitrocubane https://en.wikipedi...ki/Heptanitrocubane
#3 currently because it packs better [notexactly, Feb 26 2019]

Octaazacubane https://en.wikipedi.../wiki/Octaazacubane
#2 [notexactly, Feb 26 2019]

Cubic gauche nitrogen https://en.wikipedi...trogen#Cubic_gauche
#1 [notexactly, Feb 26 2019]

[link]






       How do you expect the yield to be 10–30% higher? I don't see you putting that much energy in just by stretching it.   

       I added links to the four best chemical explosives yet developed or predicted (IIRC), which are good examples of // already stressed at the molecular level, since they contain rings of atoms that can't adopt their preferred bond angles //.
notexactly, Feb 26 2019
  

       //I don't see you putting that much energy in just by stretching it.// For materials you're likely to encounter day to day, that's true - most materials fail at a tiny fraction of the strain (and stress) predicted solely from bond strengths and numbers. But a defect-free crystal can be strained (and stressed) much further.   

       If it helps, look at it this way. A material is held together only by interatomic bonds. If it burns or detonates, all those bonds are broken (and usually new ones are formed - the energy you get out is the difference). If you strain the material, and don't allow it to fail at a stress concentration (or to undergo slip, like ductile metals do), then you eventually reach the breaking point dictated by the bond strengths. At that point, all of the longitudinal bonds are storing as much energy as you'd get from breaking them chemically. In other words, in energetic terms, it doesn't make much difference whether you break the material chemically or by stressing it to its limit.
MaxwellBuchanan, Feb 26 2019
  

       //encapsulate them in very fine glass capillaries//   

       Even if you had 100% extra energy from stored mechanical energy, you have to add a whole lot of capillaries. These are dead weight. You also put yourself at risk of accidental detonation, breakage of a single capillary might release enough energy to detonate the content. Wouldn't it be simpler to just add extra explosive? All that glass flying around might get someone hurt.   

       I like the principle though. Maybe there are explosives that can be grown as large single crystals and pre- stressed in a casing, or internal stress could be added by tempering processes.
bs0u0155, Feb 26 2019
  

       //Wouldn't it be simpler to just add extra explosive?// Hello, [bs0], and welcome to the Halfbakery.   

       If you designed it right, the glass capillary could be stressed to its limit in compression whilst the explosive was stressed in tension, or vice versa. In that way, the capillary becomes part of the explosive.
MaxwellBuchanan, Feb 26 2019
  

       So it's only just NOT an explosion. How about other mechanical means, O2 really likes to be a gas, but if you really force it, you can make it a liquid. Maybe you could get a good ratio of say, methane to dissolve in it. Keep them in a container that ONLY JUST doesn't explode, and you have extra energy stored right there. Only you can keep it cold/drop the pressure a bit when you need to move/breathe near it.
bs0u0155, Feb 26 2019
  

       I've often wondered if you could make little micrometre-sized plastic bubbles containing liquid oxygen under intense pressure. A slurry of those in oil would make a great rocket fuel.
MaxwellBuchanan, Feb 26 2019
  

       // All that glass flying around might get someone hurt. // [+]
Voice, Feb 27 2019
  

       hmmmm, could you contain an explosive within a Prince Rupert Drop?   

       //I've often wondered if you could make little micrometre- sized plastic bubbles containing liquid oxygen under intense //   

       It can be done, I just calculated it, not in a particularly sophisticated manner, just spherical approximation from the thick-walled hoop stress formulae. A 1um sphere of O2 would need about 50 GPa to keep it liquid, that gives you a wall thickness of about 1.5mm. The rocket would run a touch rich.
bs0u0155, Feb 27 2019
  

       //contain an explosive within a Prince Rupert Drop// A P.R.D is an excellent example of a highly-stressed solid, thanks, [2fries]. The strain energy it stores is enough to turn all of it into powder. Even higher energy density is possible with small, perfect crystals.   

       //It can be done, I just calculated it// Many thanks; I knew that smaller bubbles can sustain higher pressures. What happens if you make the central void slightly bigger - is there a size that gives a higher ratio of contents to wall?
MaxwellBuchanan, Feb 27 2019
  

       I'm seeing large single-use crystal chandeliers.   

       And what about those toasts which are followed by dashing the glass into the fireplace? This idea could certainly add something there.
pertinax, Feb 27 2019
  

       There are many very good (and one truly excellent) reasons why this has never, and will never, be done - even though it is technically possible.   

       In fact, although large (multi-kilogramme) single crystals of HMX have been around for decades, after manufacture they are carefully annealed to avoid this very effect.
8th of 7, Feb 27 2019
  

       // I've often wondered if you could make little micrometre- sized plastic bubbles containing liquid oxygen under intense pressure. A slurry of those in oil would make a great rocket fuel. //   

       I feel like I just read about that very idea (or its inverse, maybe) yesterday. There was math and everything.
notexactly, Feb 27 2019
  

       //There are many very good (and one truly excellent) reasons// I am leaving the following space blank so that you can write down those reasons.   

         

         

         

       .
MaxwellBuchanan, Feb 27 2019
  

       In typical usage, one of the strengths of an explosive is its insensitivity to minor knocks.
This is why dynamite was widely used, instead of straight nitroglycerin.
  

       So I'm not sure the market for your proposed product range would be large.
Loris, Feb 28 2019
  

       It might be large but transient.
MaxwellBuchanan, Feb 28 2019
  

       No, no, don't let me stop you - feel free to go ahead with the experiment.   

       Maybe you'll be able to sweep up both the Ig Nobel prize and Darwin awards in one fell swoop. That would certainly get you into the Halfbakery hall of fame.
Loris, Feb 28 2019
  

       Wigner energy springs to mind, too.   

       Having made your crystal of stressed explosive, irradiate it with neutrons until it almost but not quite goes bang.   

       Then work out how to store it.
Wrongfellow, Mar 01 2019
  

       // I am leaving the following space blank so that you can write down those reasons.//   

       Aren't those reasons self-explodery ?   

       I wonder if a Prince Rupert Drop can be used to ignite some shock detonated explosive ?
bigsleep, Mar 02 2019
  

       ^ How are you going to collapse the Prince Rupert Drop?   

       A variable of stress that isn't in the working environment would be good. High magnetic field?
wjt, Mar 02 2019
  

       [Wrongfellow], you may take this Platinum star and affix it next to your name on the class achievement chart. Wigner energy is absolutely spot on.
8th of 7, Mar 04 2019
  

       //many explosives are already stressed at the molecular level// I'm currently able to stop just short of throttling the near-terminally stupid...oh dear, I may be the personification of this idea.   

       //if you had 100% extra energy from stored mechanical energy, you have to add a whole lot of capillaries// This idea explains the growing network of spider veins (not possibly due to the Collingwood Select), and the throbbing vein appearing intermittently just over my right orbital socket at times of maximum stress.   

       //little micrometre-sized plastic bubbles containing liquid oxygen under intense pressure// News reports say that every living thing on Earth--even the unnamed citizens at the bottom of Mariana Trench--now contains plastic. So, every time I breathe, I pressurize these plastic bubble beads.   

       Stand back.
Sgt Teacup, Mar 04 2019
  
      
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