|
Boozehawk
|
|
|
Group: Forum Members
Posts: 7,
Visits: 23
|
This guy gives a good comparison of CF KvLr v FG from an engineering perspective. https://www.youtube.com/watch?v=KHXVf0SaJpA
|
|
|
|
|
Boss
|
|
|
Group: Forum Members
Posts: 15,
Visits: 185
|
|
|
|
|
|
Boss
|
|
|
Group: Forum Members
Posts: 15,
Visits: 185
|
I'm not an expert on any of this, as my role in the business was administrative, but I do know there are two primary resin systems used in composite armor.
One uses thermoset resins, the other uses thermoform resins, and materials like Kevlar, Spectra, and Polystrand primarily use thermoform resins allowing the consolidation to remain flexible as it catches the spall.
Thermoset resins are used in spall liners as well and the one I'm most familiar with is called the HJ1 System, which is licensed by AGY. It is a consolidation of S2-Glass using uria-formaldehyde resins and the armor is and very hard.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Very interesting stuff. I don't know much about armour, so it's great to read such a good piece of info from someone in the know. The theory does seem to differ somewhat from the experience I have with composites and impacts, and I would wager that is due to the high energy point losing that is involved with stopping bullets and projectiles. My experience is mainly in the mining sector, I was involved in a project making carbon fibre haul pack trays. The impact loading is somewhat different, very large and heavy rocks and debris being dropped onto the tray. The theory here is that a composite laminates ability to resist an impact is it's resistance to deflection. The brittleness of carbon fibre comes from the fact that it has extremely poor elastic performance, so any failure is catastrophic. In order to resist failure, the laminate needs to be able to take the load without deflecting past its plastic loading capacity. Hence, stiffness is key and carbon fibre is the best material for it. In this situation, Kevlar is a poor choice due to its very poor compression properties, and there is no use for its higher elastic performance in a hail pack tray.
|
|
|
|
|
Zebra
|
|
|
Group: Forum Members
Posts: 14,
Visits: 32
|
It's all about selecting the right material for the job. Carbon fiber is used in cars because it's rigid, strong and light. Car's aren't made to be "impact resistant" in the same way as a bullet proof vest. They are designed to crumple up and take the force of the impact, leaving the driver intact, but not necessarily the car. Because cf is so strong, light and rigid, it's great for cars, planes and rifle stocks (what I use it for). Materials like Kevlar and fiberglass require far more layers to become rigid so parts end up heavier and heavier parts make baby Jesus cry... Because they aren't rigid, fiberglass and Kevlar will bend more before they break so, they are useful where those properties are desirable. Kevlar is incredibly annoying to work with. Cutting it hurts your hands and breaks your tools. It's impossible to sand. I avoid it wherever possible.
|
|
|
|
|
Boss
|
|
|
Group: Forum Members
Posts: 15,
Visits: 185
|
Having been in the armor business for a number of years starting right after 9/11, we found that carbon fiber was two brittle. Armor consists of multiple layer constructions where each layer plays a specific role in defeating the threat.
The role composite armor plays in that sandwich could be likened to a catcher’s mitt. Armor generally consist of a strike face, which is something like AR500 steel, then has a ceramic plate behind it, and the composite materials are the last layer.
Depending on the threat, the projectile passes through the steel, which deforms it giving it a larger footprint and slows it down, the ceramic breaks the projectile into smaller pieces called spall, and the composite referred to as a spall liner catches the spall.
I’ve attached an image showing a .30-06 caliber armor piercing incendiary round lodged in a consolidation of Spectra and Polystrand. Polystrand is S2-Glass that is laminated in 0° / 90° cross bands, with each corresponding layer being in that same orientation.
The composite portion of this armor consolidation was about a .250” thick. The other two layers were .125” thick each and consisted of AR500 and ceramic. This armor layup weighed 7lbs per sqft, and stopped the round within 15’ of target, traveling at 2800 ft per sec.
This particular armor was for a riverine gunboat, which I've attached a picture of.
I’ve also attached a picture showing a consolidation of pure Polystrand used in the .500” thick AR500 floor of armored tactical vehicles. This is the spall liner that is combined with the steel, which is used to defeat mines and IEDs. You can see the thickness in relationship to the dime. In all the testing we did, we never found carbon fiber to be a suitable material for armor, but Kevlar is used a lot as it has good flexural strength. 
|
|
|
|
|
scottracing
|
|
|
Group: Forum Members
Posts: 460,
Visits: 5.2K
|
In f1 the anti intrusion protection panels are made from Zylon, which is similar to Kevlar but has better properties. It was used in bulletproof jackets for a time until they realised it aged and the properties of it reduced rapidly. Unfortunately it wasn't found out until a police office was shot in the US and the bullet passed through. Oh and zylon is one of the worst types of prepreg to laminate and cut, absolute pig of a material.
|
|
|
|
|
Dravis
|
|
|
Group: Forum Members
Posts: 592,
Visits: 1.9K
|
@ArturK ...
You may want to study that a bit more before making such brash statements ...
Aluminium honeycomb has close to zero "impact resistance" on its own .. -- but it can be used to construct "impact absorbing cell structures" by combining the honeycomb with stronger materials in carefully constructed "crash cells" --
The primary purpose of Nomex/kevlar honeycomb or Aluminium honeycomb is to provide an ultra lightweight "filler" for sandwich-panel constructions, that has high strength in the cross-section direction.
In effect it creates a very stable distance between the two or more sandwich panel layers -- Stiffness of a given sandwich panel increases dramatically with the distance between the "skins"
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
I haven't come across Ali honeycomb in a street-oriented production car... Ali honeycomb is certainly used for intrusion protection in motorsports, but it is often a composite sandwich laminate, generally carbon fibre. Have seen Ali honeycomb with Ali skins, but that's super heavy stuff. Useful in a front crash box structure. Technically speaking, the only reason Kevlar is better in an impact situation is because it maintains a degree of elasticity. Carbon fibre has a higher tensile strength and better plastic performance, but absolutely no elastic performance. So in the event of catastrophic failure, carbon fibre is broken and no longer offers any sort of protection. Kevlar however will maintain some strength once broken.
|
|
|
|
|
ArturK
|
|
|
Group: Forum Members
Posts: 19,
Visits: 53
|
In sport cars impact resistance is guaranteed by aluminium honeycomb, not by carbon fiber or even kevlar.
Carbon fiber sheets and composites . www.dexcraft.com
|
|
|
|