Hi, lady here who owns and wears armor sometimes. There are a few things wrong with this.
(Prefacing that only a very very small number of women historically wore armor)
You'll find that basically ALL medieval plate bulges out in the chest. That is specifically because dome shapes are stronger, but also for ease of movement. A flat plate will make it harder to bring your shoulder back (or you'll need to make a bigger arm hole).
You'll also find that most people who do stuff while in plate armor tend not to carry a lot of fat, and since boobs are mostly fat, women who wear armor "for a living", and are thus swinging pole arms quite a lot, tend not to be very busty.
Thirdly, the main difference between my armor and the armor the guys are wearing is not in the plate, but in the padding underneath. I have a gambeson and armor coat that is thicker above and above my breasts than right in front. There's basically a boob-slot in the padding, so that a hit to my chest gets absorbed by my body instead of my boobs.
I'm so glad you wrote all of that, and so much better than I could have. Men have no idea of the ways in which breasts need support, or how generally the better it looks, the less comfortable it is.
@Tar_alcaran@Shivirani The typical breastplate shape is what I call the "Robin's breast," a swollen dome shape that protects the vitals from strikes to the body center.
So does that mean if my husband gets armor I could wear it too, I'd just need a different gambeson? My breasts protrude a couple of inches even in a sports bra.
Also, added chest muscle makes your boobs stick out more...
Is a breastplate/gambeson/armor coat etc something you can effectively buy online, or is it something you want to try on in-store before you buy? And where did you get yours from?
Buying armor is like buying a suit, and all the answers are kind of similar.
You can get a cheap mass produced one, but it won't fit as well as a tailored one, and that won't be as good as a custom made one. You can wear someone else's (within reason), as long as they're mostly the same size, but it won't be great.
A gambeson or arming coat (typo before) is similar, off the rack is fine, but it'll fit much better if you have it custom made. And like bras, being a woman is expensive here. I bought a good one and modified it myself.
I got my armor custom made by a guy in Ukraine like 15 years ago, the whole thing was 6000 euros which was a huge bargain. But if you just want a breastplate for occasional use (larp, cosplay, etc) getting one online and accepting it's kinda awkward is very much an option. If you need it to actually stop swords (reenactment, HEMA) that's still an option, but you'll need to be much more selective.
Hits to full armor aren't about cutting through or breaking the armor, but trying to get as hard of a hit as possible. One central outward curve will deflect hits.
Two bulbous curves next to each other will deflect hits on the outside but focus hits on the inner curve into a shape that will ensure all of the power in the hit goes right to the chest. A great way to ensure the wind is knocked out of the wearer.
Plus, the biggest concern regarding the deflection of blow by plate armor was lances. A lance blow is often described as having the momentum of both the rider and the horse behind it (not quite true, but certainly more than just the knight). That is a lot of force for a body to absorb