You say the metallic fibers are loosely bonded (almost glued) to the substrate.
You should not use beam elements for this because nodes on beam elements have 6 DOF while nodes on solid elements only have 3 DOF. That means if you have a line of nodes in the substrate that are shared between the solid and the beam, the beam gets no support for rotation about the axis of the beam. Model the metallic fibers with solid elements.
Is the tensile test going to apply a sufficient displacement to cause the bond to fail? If the answer is yes, then you don't want to merge the nodes on the fiber elements to the nodes on the substrate elements, since there will be no way for failure to occur.
There are several methods to model debonding in Static Structural (not Explicit Dynamic). One uses Bonded Contact. Read the Ansys Help manual on Debonding. Open Ansys Help, then copy paste the text below into the URL address bar at the top.