UD composites consist of an isotropic linear-elastic matric material and an isotropic or transversely isotropic (in 1 direction) linear-elastic fiber material.

Fibers are infinite, cylindrical, and have the same fiber diameter.

Fibers are perfectly aligned with the X-axis of the RVE.

Fibers form a regular (periodic) pattern.

Bonding between the fibers and matrix material is perfect.