My favorite subject !!! ARMOR!!!! hehehe
Well it is possible to build fake standing armor statues..but wearable armor..i wouldnt advise papier maché ..most of my good friends either run or distribute items to dungeons & dragons outdoors or medieval events and believe me when i say ..we have tried EVERYTHING has armor components hehehe so i would strongly recommend you NOT to use papier maché has armor BUT!!!! you can use it to make the base piece for building one in another medium.

I dont know whats the real word for it but we call it shirt transfers..you basicaly mold in 2 parts the shape of one's chest in papermache mixed with plaster over a used t-shirt ( the front part and back part ) here's the basic idea and steps to do it if your interested:

1 : the person you want to mold puts on an old t-shirt and lays down on his back on a table or other strait surface ( put a opened up garbage bag at the seam over the table first )

2 : make a line from beneath the arm pit to the bottom of the shirt on eahc side of him with masking tape and from the neck to the end of the sleeve on each side

3 : cover the front of him with papermache pulp mixed with plaster , when its done use a hair dryer and dry it out for a good 15 to 20 minutes.

4 : grab delicaly the edges and gently pull it off

5 : use a laundry basket filled with old towels and cover them up with news paper so that when you put the piece on it they take up the form of the piece so it dosent warp while drying.

6 : do the back and repeat steps 3 to 5

7 : when everything is perfectly dry ( 1 to 2 weeks ) cut and sand down the edges so the meet perfectly together ( front and back ) and glue them together

Voila you have a perfect shape of the bust for whom you wish to build an armor for : )

Yeah i am french : )
if you want more info on the subject just e-mail me

Plastic and polyuretane are good one's..check my provider listing post for more info : )