Do i need fresnel node for principle shader???
No. Fresnel is built into the principled BSDF. The specular slider controls it’s effect.
Glad to help.
By the way, if you prefer working with physical IOR values in the specular slider, there’s a formula in the Blender manual:
It’s the first hint in green. The default value is fine in most cases, but it’s there if you like to get technical.
You may want to use it if you mix the principled with a manual glossy (topcoat) shader, as it’s builtin topcoat is (was?) buggy wrt topcoat roughness in that it can’t be properly texture mapped (it stays at zero until a certain threshold is reached creating a sudden change in roughness).
If you’re mixing with anything else, you probably should use a different way of mixing, as fresnel is only for splitting “what goes into the object” and “what is bounced off the object”.