Fiber Glass Tank

Dear All, Thanks for attention,

Iam doing fabrication for chemical injection skid, our client requirement for the tank is fiber glass (FRP), Iam trying to calculate the thickness for the tank, I found API 12P for FRP tanks and it have formula for thickness calculation but it require the S (stress value) and the code indicating ASTM D638, but I coud't find this code, my question is:

1- If any one have ASTM D639 please pass it to me,

2- I think there are alot of types of FRP is it mean that there are several values of stress?

Thanks