Heckler & Koch G36: the rifle held in all the wrong places
http://www.dw.de/heckler-koch-g36-the-rifle-held-in-all-the-wrong-places/a-18402772
I found the referenced article interesting about the problems the Bundeswehr is having with the H&K G36. New material technologies have been introduced in the last couple of decades, the Glock leading the bow wave for polymers and pistols. After reading this article it seems H&K made use of polymer composites on their G36, to lighten the weapon, but according to the article the plastics are overheating. As far as I know plastics don't expand on heating, such as metals do, instead thermoplastics turn back to a liquid and thermoset plastics char. I suspect the G36 receiver is a thermoplastic as plastics are a lot cheaper to fabricate. Cheap coke bottles and similar items are made of thermoplastics, machines can blow them into a mold. Thermosets take a lot of hand labor and therefore are costly. It has been a long time since I looked at the material properties of thermoplastics, but it is my recollection only a few can be considered "high temperature" and those temperatures were not anywhere near the glowing red of a steel barrel. My guess, based on this article, is that the Germans never required or tested the G36 to the point where cartridges would ignite in the chamber to heat, and therefore their requirements never took into account the heat load that can happen under extended combat conditions. In combat, their weapons were melting.
Before any Americans feel smug about any supposed inherent National superiority, let me show this American made all plastic AR15 receiver. This came out into the market a few years ago. The manufacturer simply copied the dimensions of an aluminum AR15 receiver and poured the thermoplastic into a diminsionally correct mold. It is obvious that the American manufacturer never considered the material property differences between aluminum and discontinuous fiber reinforced plastic, nor the stress paths. The end result was that once loaded up with barrel, bolt, buttstock, these plastic receivers cracked.
However, they were good enough to quickly replace all these design defective receivers with an improved version. If you notice, there is an metal insert where the previous receivers broke.
.
http://www.dw.de/heckler-koch-g36-the-rifle-held-in-all-the-wrong-places/a-18402772
I found the referenced article interesting about the problems the Bundeswehr is having with the H&K G36. New material technologies have been introduced in the last couple of decades, the Glock leading the bow wave for polymers and pistols. After reading this article it seems H&K made use of polymer composites on their G36, to lighten the weapon, but according to the article the plastics are overheating. As far as I know plastics don't expand on heating, such as metals do, instead thermoplastics turn back to a liquid and thermoset plastics char. I suspect the G36 receiver is a thermoplastic as plastics are a lot cheaper to fabricate. Cheap coke bottles and similar items are made of thermoplastics, machines can blow them into a mold. Thermosets take a lot of hand labor and therefore are costly. It has been a long time since I looked at the material properties of thermoplastics, but it is my recollection only a few can be considered "high temperature" and those temperatures were not anywhere near the glowing red of a steel barrel. My guess, based on this article, is that the Germans never required or tested the G36 to the point where cartridges would ignite in the chamber to heat, and therefore their requirements never took into account the heat load that can happen under extended combat conditions. In combat, their weapons were melting.
Before any Americans feel smug about any supposed inherent National superiority, let me show this American made all plastic AR15 receiver. This came out into the market a few years ago. The manufacturer simply copied the dimensions of an aluminum AR15 receiver and poured the thermoplastic into a diminsionally correct mold. It is obvious that the American manufacturer never considered the material property differences between aluminum and discontinuous fiber reinforced plastic, nor the stress paths. The end result was that once loaded up with barrel, bolt, buttstock, these plastic receivers cracked.
However, they were good enough to quickly replace all these design defective receivers with an improved version. If you notice, there is an metal insert where the previous receivers broke.
.