What does the [2/4/4/2] notation in composite ply layup represent?

[Dave-Eng]

Hi,
I've come across this notation to describe a composite ply layup:

[2/4/4/2] – [45/0/-45/45/90/-45]s

I know that the second part is notation for: [45/0/-45/45/90/-45/-45/90/45/-45/0/45]
But what is the [2/4/4/2] in referrence to?

I have noticed that 2+4+4+2 = 12, and there are 12 ply orientations but I don't know if that is coincidence.

Thanks for any help people can share on this.

 

[Dave-Eng]

Hi Dave-Eng, I think I've just answered your own question:
The [2/4/4/2] refers to the number of plies of each orientation [0/+45/-45/90] respectively.
You could also argue that this is completely redundant because this information is captured within [45/0/-45/45/90/-45]s