I'm quite well versed in how medieval armour evolved throught the centuries, so I have a pretty good picture of how a rich knight would be armoured at each time in the medieval period, but I would like to ask you how the average man-at-arms or levied peasant was protected (I assume a gambeson, mail coif, and some sort of kettle helm or Norman helm with noseguard?)
Also, I have found conflicting reports in academic writing about the composition of medieval armies. Some sources suggest that levied peasants made up a tiny percentage, if any at all, of an army, while others consider them to form the basis. I obviously realize that this must have varied throught the period, having much less unspecialized infantry in the Late Middle Ages, than in the High Middle Ages
Thanks.
This recent question on /r/AskHistorians has some discussion about the composition of Medieval armies, which should give you some input on the second part of your question. It also touches on some of the equipment levied peasants might be equipped with:
http://www.reddit.com/r/AskHistorians/comments/37dzi3/during_medieval_warfare_what_equipment_and/
I don't have time for a full answer right now, but I might tomorrow if you give remind me. I'll try and answer some of your questions in brief, though.
We don't know a huge amount about what the average soldier would have been equipped with in the Early or High Middle Ages since sources don't really talk about them very much. As you've mentioned we know a decent amount about the nobility but how far down the social track things like chain mail and high quality swords would have gone is not always readily apparent. This significantly improves in the Later Middle Ages.
The other big problem with talking about army composition is that it changes drastically by kingdom and time period. As an example, for much of the Hundred Years War England used semi-professional soldiers who were recruited specifically for campaigns. In contrast France was still using more traditional peasant levies in part because the French King lacked the sophisticated tax system of the English and couldn't afford to pay for the kinds of armies the English had. Near the end of the same war, though, Charles VII established one of Europe's first permanent standing armies thanks to some serious reform of the tax law.
While it only deals with one specific case study Michael Prestwich's Infantry Warfare in the Fourteenth Century: The English Experience is well worth a read for its in depth discussion of this subject. His bibliography should also suggest good further reading options.