A Flitch beam is also known as a flitched beam. These types of beams are made of more than one material. A Flitch beam is a composite beam.
It is consist of two layers.
Example: A composite beam made of steel and wood.
Composite beams can be analyzed using the same bending theory used for general beam analysis. This is because the assumption that a cross-section that is flat before bending remains flat after bending is true in pure bending regardless of the material.
From this assumption, it can be seen that the longitudinal strain varies linearly from the top to the bottom of the beam. The location of the neutral axis need not be the center of gravity of the cross-sectional area. For multi-story beams, the cross-section is doubly symmetrical and the neutral axis is located in the middle of the section.
Here is another pic of Flitched Beam to understand better.
Flitched beams are double-layer composite beams made of wood and steel as shown above.