Importing a smooth skeletal mesh in ue4 from Maya

I am trying to import my character in ue4 from Maya, in Maya all the parts of the character look smooth. However, when I import the character in UE4 it is a different story for the hair.
I have been searching for 2 days.
I tried to select the mesh and press 3 in Maya then select the mesh and delete deform history, and export the mesh with the skeleton with and without smooth groups and smooth mesh but the result is one, the hair is still not as smooth as it supposed to be.
in UE4 I tried import Normals and Tangents but nothing has changed!