The second word of the Dragon Aspect Shout is located at the Raven Rock Mine. This is near Raven Rock. To get to the mines from Raven Rock, start from the Raven Rock Docks and go out towards the stairs but dont climb the stairs instead go left, and keep going and climb a road going up to the entrance to the mine, here is what the mine entrance looks like:
There you find Crescius Caerellius who gives you a quest to retrieve his great grandfather's journal. This will lead you to the area where the word is. On the way you will pick up a sword that shoots waves of energy, which you will need to open a special door. Use the sword to do a power attack on the red lines on the edge of the doors, then a vertical attack on the central seam of the door.
You will fight a dragon priest called Zahkriisos and in a big chamber where the black book is, you will find the second word of power, Armor:
WORD OF POWER LEARNED - ARMOR, DRAGON ASPECT